In this study the material from “Five year study of Epidemiology of Tuberculosis” (1961-68) has been analysed to find out an improved method of interpretation of chest X-rays to get accurate estimation of prevalence of “suspects” in the community. The population of a random sample of 119 villages from the three taluks of Bangalore district was surveyed four times with intervals of 1½ to 2 years by tuberculin testing, 70mm chest photofluorography and sputum bacteriology. Out of 45,434 persons X-rayed during the first survey, 590 were read as active pulmonary tuberculosis on the basis of single picture interpretation by two independent readers. Of them, 460 being sputum culture negative were classified as initial “suspects” and these were reviewed in this study by the panel of three readers together by the method of “joint reading”. The interpretation was done comparing the serial X-rays of individuals taken at intervals along with other available examination results and personal data. Out of 460 initial suspects only 110 (23.9%) were confirmed as “suspects”, the remaining were judged as non-tuberculous and/or inactive tuberculous (62.2%) and normals (13.9%).

Fates on five year follow up were compared between 85 “confirmed suspects” and 385 “initial suspects”. The mortality and sputum positive status were found more among the former group i.e., 23.5 and 25.5 and 14% and 7.2% respectively. Radiologically, 48.7% of the confirmed suspects and only 10% of the initial suspects could be classified as suspects at 5th year follow up. Incidence of bacillary disease among the confirmed suspects was also found higher. On the basis of “joint reading” and five year follow up study, the limitations of single picture interpretation resulting in considerable over diagnosis were clearly seen. The comparative reading of serial X-rays along with other examination results did help in the better assessment of etiology and activity status of disease. Of the X-rays read as non-tuberculous and inactive tuberculous when reviewed by “joint reading” method, about 67 more suspects could be added. Even then the estimates of prevalence of “suspects” based on single film interpretation which are widely used in India appear to be about 3 times the actual prevalence.

Some of the parameters relating to duration of infected status and incidence of disease have been measured by analysing the data collected from the five year study. Between 1961-68, 119 villages in Bangalore district with total average population of about 62,000 were surveyed at intervals of 1, 3 and 5 years from the first survey. All persons were tuberculin tested with 1 TU RT 23 and those aged 5 years or more were X-rayed. Sputum of those persons showing any X-ray abnormality were collected and examined for AFB. Persons with X-ray abnormality but bacteriologically negative or with normal X-ray in all the preceding surveys, and who became culture positive with X-ray abnormality in the current survey were termed as "New cases". New cases who had shown 10 mm or more reaction to 1 TU RT 23 at I Survey were considered infected previously. New cases, tuberculin negative at I survey but who showed an increase of 16 mm or more between two consecutive surveys were considered infected midway between the two surveys.

Of the 42 new cases diagnosed from among the newly infected during 5 years, 81% came from those infected within one year. Incidence rate of cases among those who were infected within one year was about 5 times more than those infected earlier than one year. Incidence of cases steadily decreased with the increase in the duration of infection. Further, it was found that one fourth of all newly diagnosed cases came from the newly infected persons. However, the size of the pool of previously infected persons in a community being much larger, at least 72% of the new cases came from the reservoir of previously infected persons. The incidence of disease among the newly infected was almost the same in the three age groups i.e., 5-14, 15-34 and 35 years or more. But, the ratio of the incidence rates for the newly infected and the previously infected decreased from 13 for the age group 5-14 to 3 for the age group 35 years and above. In other words, the incidence of disease among the newly infected in the age group 5-14 was thirteen times more than for the previously infected in the same age-group whereas in the age-group 35 years and above, the incidence among newly infected was only thrice that among the previously infected.
Out of the 160 new cases diagnosed during the three repeat surveys, 21 per cent cases came from among those who were infected on the average for one year or less. This is almost in conformity with the hypothesis that one-fourth of all new active cases come from new infections less than a year old.

The five year longitudinal epidemiological study in south India (1961-68) showed that a considerable proportion of bacteriologically proven cases found in a survey got cured naturally without the facility of organised treatment in the survey area. This "natural cure" could be an epidemiologically significant phenomenon- depending on the stability of such a cure or in other words, the frequency of relapses among the naturally cured. In all, 108 naturally cured cases of tuberculosis out of a total of 269 cases, from among about 62,000 persons surveyed twice, were followed up for varying periods of 1 to 3½ years.

It was observed that the average relapse rate was 85.4 per 1000 person years of observation, there being no difference between the two sexes. Relapse rates were however higher in persons aged 20 and more compared to those 5-10 years old. Relapses were not dependent on the bacteriological status at initial diagnosis i.e., whether positive by culture alone or positive by smear and culture. The death rate among the naturally cured was 42.7 per 1000 person years and together with relapse constituted the unfavourable fate after natural cure. It has been calculated that as an input, adding to the pool of bacillary cases in the community, the ratio of relapse cases to cases arising afresh from the general population in a year would roughly be in the order of 1:16. It is concluded that the naturally cured status could be considered as an epidemiologically favourable situation, though much less so when compared to the chemotherapeutically achieved cure.

The study was undertaken in a sample of 103 villages of 3 sub-divisions of Bangalore district as a part of the 5 year study of epidemiology of tuberculosis between 1961-68. The follow ups were done at 1.5, 3 & 5 years after the first survey. The entire population was offered tuberculin test with 1 TU RT 23, a second test with 20 TU RT 23 to those persons who were having reactions of 0-13 mm to 1 TU. All aged 5 years or more were offered 70mm photofluorograms at each survey. Two specimens of sputum were collected from persons having abnormal X-ray shadows for examination of tubercle bacilli. Procedures were uniform at each survey. The population was divided into three groups on the basis of their tuberculin reactions: (a) reactors to 1 TU (infected with M.tuberculosis), b) non-reactors to 1 TU but reactors to 20 TU (infected with atypical mycobacteria), c) non-reactors to both 1 TU & 20 TU (not infected with either M.tuberculosis or other mycobacteria). Incidence of disease and crude mortality were studied separately among these groups.

The five year incidence of culture positive disease was the highest among 1 TU reactors and the least among reactors to 20 TU. In the younger age group (5-14 years) the five year incidence of culture positive disease among reactors to 20 TU was significantly lower compared with that among 20 TU non-reactors. The reduction of incidence of culture positive cases in the former group over that in the latter was 75% for culture positive cases and 61% for combined culture positive and negative disease. As regards crude mortality, the overall rate was significantly lower among 20 TU reactors compared with non-reactors. Even if the significance of the finding on crude mortality is debatable, it could be concluded that non-specific infection provides some protection against development of tuberculosis, at least in younger age groups.

The data from a tuberculosis prevalence survey carried out in three taluks of Bangalore district in south India during 1961-68 were analysed to study (i) the prevalence of non-specific sensitivity in the community i.e., prevalence of infection with mycobacteria other than M.tuberculosis, as found by testing the population with tuberculin RT 23 of a lower strength (1 TU) and higher strength (20 TU), both with Tween 80 and (ii) additional boosting if any, resulting from testing with higher dose of tuberculin, immediately following a test with 1 TU RT 23.

The level of demarcation between infected and uninfected with 1 TU was 0-9 mm induration size and this negative group tested with 20 TU dose induration of 8 mm or more was considered positive. Prevalence of infection with M.tuberculosis in the community were 2.1% in 0-4 years, 7.9% in 5-9 years, 16.5% in 10-14 years, 33.2% in 15-24 years and overall 14.5% in 0-24 years of age group. Infection rate with other mycobacteria were 12.9%, 44.9%, 66.2%, 62.4% and 45.7% respectively in the above stated different age groups.

Testing the population with 20 TU RT 23 following a 1 TU test was found not to boost the tuberculin reactions over that observed on a single test with 1 TU only.

The study was undertaken among 22,957 persons belonging to 55 randomly selected villages of Nelamangala taluk of Bangalore district in 1975, to find out precise estimates of prevalence of bacillary disease. Symptom screening was done by well experienced social investigators, according to a brief interview schedule. Sputum was collected from all above the age of 5 years reporting chest symptoms for seven or more number of days during the previous two months. Within two weeks after symptom questioning, all were tuberculin tested and all 5 years and above were X-rayed. Additional sputum collection was done for those asymptomatics who had abnormal shadows in their chest X-rays.

The overall prevalence rate of culture confirmed bacillary cases by symptom and/or X-ray screening was 0.32 percent. Same prevalence was seen with X-ray alone also. But the overall prevalence rate based on symptom screening alone was 0.21 percent which is significantly lower than that of symptom and/or X-ray screening, or X-ray screening alone. The prevalence rates by age and sex based on symptom screening were about two-thirds that of rate based on X-ray and/or symptom screening. Hence to obtain prevalence rate according to X-ray and/or symptom screening, a correction factor of 1.52 should be applied to the prevalence rates obtained by symptom screening alone. This correction factor is fairly good for most of the age groups. It was also estimated that the cost of surveying the population by symptom screening alone is about half that of surveying the population by X-ray screening.

A study was conducted in a slum area of Bangalore, to get information on the prevalence of all forms of tuberculosis in 0-4 year age group, respiratory tuberculosis in 5-14 year age group and the proportion of respiratory tuberculosis among total respiratory diseases in 0-14 year age group. Entire population in a slum area was investigated. Children aged 0-9 years were given tuberculin test and their nutritional status assessed. All persons were X-rayed. Sputum specimens were collected from those having radiological abnormality in chest, chest symptoms of one week or more in 0-4 years, in addition from those with any kind of sickness, malnutrition and tuberculin reactors.

In 0-9 year age group, 5.5% were tuberculin positive (without BCG lesions), in 0-4 years, 1.8% and 5-9 years, 11.3%. Among the X-rayed children, 47.4% had some kind of sickness, the proportion being significantly high in 0-4 year age group. The respiratory sickness is the commonest among children of all ages followed by malnutrition (21%). Among children with chest symptoms, upper respiratory infections were 33%. Chest X-ray abnormalities were present in 4.5% of children and of these 82.5% had non-specific pneumonitis. Of 71 persons with respiratory disease, about 7% were tuberculous. Out of 1408 children, only 5 had active primary tuberculosis, giving a prevalence of 0.35%. None in 0-4 year age had sputum positive disease or extra pulmonary tuberculosis.

It has been highlighted that non-tuberculous chest diseases are common in pediatric age group and many of these may be wrongly classified as active tuberculous in practice. It is concluded that tuberculosis in the pediatric age group in this community is not a serious public health problem.

Estimates of prevalence of non-specific tuberculin sensitivity in south Indian population are based on studies using large doses of tuberculin prepared from Mycobacterium tuberculosis. In the present study, comparison of tuberculin test done on 2168 children aged 0-9 years with 20 TU RT 23 and 5 TU Battey antigen, belonging to rural areas, have been done. The distribution of induration to 20 TU RT 23 test has been compared to that of 5 TU Battey test, to see whether estimates of prevalence of non- specific tuberculin sensitivity based on the former could be compared with those based on tests with antigen derived from other mycobacteria.

It was seen that distributions of reactions, mean size of indurations as well as percentages of positive reactors to either test were not significantly different in the two randomly selected groups i.e., one tested with Battey antigen and the other with 20 TU RT 23. The prevalence of non-specific sensitivity in 0-4 years age group based on Battey test was 18.4 per cent and that with 20 TU test, 16.6 per cent. In the age group 5-9 years corresponding rates were 54.2 and 60.1 per cent. From these observations, it is suggested that if other antigens are not available, 20 TU RT 23 could be used for estimation of non-specific sensitivity.

Because of slow nature of decline and the long span of the declining phase spread over a couple of centuries it is difficult to obtain direct evidences of decline by conducting studies over relatively short period of time and comparing the rates so obtained. Therefore, one has to take into account the total current epidemiological situation by considering both indirect and direct evidences to know the trend of disease; A) Indirect Evidence i) tuberculosis morbidity being largely confined to older age groups, prevalence rates being similar in both rural and urban areas and a wide gap between infection and disease rates (38% and 0.4% respectively). ii) Information on tuberculosis mortality although not very reliable, still appears to suggest that the disease, since the turn of the century, has taken a declining course. It has been observed to be 253 for 100,000 persons in 1949 in Madanapalle and 84 per 100,000 in Bangalore during 1961-68. There might he some regional variations but there is definite suggestion of decline in the mortality. iii) Considerable change in clinical presentation from more acute and exuberative to a more chronic disease and a shift in age during last quarter of the century, a marked decrease of the concomitant problems of pulmonary tuberculosis, are all indirect indicators of decline. B) Direct evidences are: i) Information available from various epidemiological surveys in India indicates no change in the prevalence rates of bacillary tuberculosis in the country during the last two decades. ii) The longitudinal survey conducted in south India and the other in Delhi have shown a declining trend of the disease specially in the younger age group. However, to see that the trend is secular or not, these surveys have to be continued for a longer period of time - atleast 15-20 years.

From the above evidences it may be reasonable to infer that there is a gradual but slow natural declining trend of tuberculosis in the country. To hasten the process of natural decline and to give relief to a large number of prevailing cases, anti tuberculosis measures should be further strengthened.

Out of 56,146 persons without BCG scar examined at the first survey in 119 villages of Bangalore district (1961-63), 22,468 were subsequently examined 3 times over a period of five years by tuberculin test, X-ray and sputum at intervals of 1½ years to 2 years. No organized anti-tuberculosis services were provided in the study area. On the basis of tuberculin status and chest X-ray interpretations, the population was classified into 6 sub groups for the study of risk of sputum positive disease viz., Normal X-ray (N), Inactive Tuberculosis (AB) & Probably Active Tuberculosis (CD) and each of these into tuberculin positives and negatives.

The annual incidence of sputum positive disease observed was 1.45 per thousand among 18,207 eligible persons aged 5 years and more. The incidence of the disease in tuberculin positive group was 7 times as compared to that among tuberculin negatives. The incidence rate of bacteriological disease was 0.79 per thousand among X-ray normals (N) of the first survey; it was 3.73 per thousand among persons with inactive tuberculous lesion and non- tuberculous shadows (AB) and 26.04 per thousand among the group of persons with active or probably tuberculous shadows (CD). Of the total incidence cases, 76% were contributed by the tuberculin positives. The group of active or probably active shadows (CD) contributed 26.6% of the total new cases. The population without any radiological abnormality (N) contributed 48.2% of the new cases.

A study was carried out mainly to find out the prevalence and incidence of sputum negative active pulmonary tuberculosis (suspect cases) among 35,876 persons aged 5 years and above in rural areas of Bangalore district during 1968-72. Two surveys (I & II) at an interval of 3 months, succeeded by a follow up examination of the X-ray abnormals of the earlier surveys, were conducted in the same villages. Examinations at each survey consisted of tuberculin test, X-ray and sputum examinations. X-rays were interpreted individually at the time of each survey by single picture interpretation method and subsequently by Joint Parallel Reading (JPR) method to arrive to a diagnosis. In the JPR method X-ray readings and their comparison was done by a panel of three X-ray readers with full knowledge of age, sex, result of sputum examination and tuberculin test of each person with chest abnormality at any of the three surveys.

On a single picture interpretation the overall prevalence rate of suspect disease was found to be 5.4 per thousand at I survey and 4.59 per thousand at II survey. There was no significant difference in the overall age and sex specific prevalence rates of suspect disease between I & II surveys. Incidence of suspect disease at the end of 3 months was 2.24 per thousand. By JPR method the prevalence rates of suspect disease was 3.2 per thousand at I survey and 3.6 per thousand at II survey. The prevalence rates by single picture method were overestimated to the extent of 38% at I survey and 19% at II survey when compared with those found by JPR method. At I survey prevalence rates on JPR method was significantly lower than by single picture method. This was not so at II survey. Similarly, incidence rate of 0.2 per thousand of suspect disease on JPR was about 1/10th of that found by single picture method.

The incidence of bacteriologically positive cases in 6 months from among suspect cases on JPR was found to be 28%. Majority (76%) of non-tuberculous or inactive tuberculous shadows continued to remain as such after 6 months and about a quarter (23%) became normal. Incidence of bacteriologically positive cases from this group was minimal. Of 19,640 persons with normal X-rays 134 (0.7%) developed new shadows in 3 months; 103 (0.5%) cleared after 2-12 weeks (fleeting shadows). Mis-interpretation of the latter as active tuberculous may falsely boost the estimates of suspect disease to the extent of about 5%.

Information on cause specific mortality rates due to tuberculosis in India is inadequate. In the study under report, these have been estimated based on the data obtained from a five year epidemiological study of 119 villages of Bangalore district in south India. For this purpose, the estimated number of excess deaths due to causes other than tuberculosis among patients of tuberculosis, have been attributed to the disease.

The annual mortality due to all causes on 5 year observation could be calculated as 893 per 1,00,000 population (9%) aged 5 years and above. Agewise as well as overall mortality rates were not different from survey I & II, II & III & III & IV. The average rate of the periods is calculated to be 84 per 1,00,000 annually. The death rates were the highest in 55 years and above age groups, lower in 5-14 years and showed an increasing trend with age. Compared to the estimates of tuberculous deaths in India available for 1949 (about 250/1,00,000), the present rates were lower.

The incidence rates of sputum positive pulmonary tuberculosis (cases) from the five year follow ups of a rural population done by National Tuberculosis Institute were reported on the basis of studies at intervals of one and a half to two years. Information on fate of cases was also likewise reported. These parameters appear to be imprecise since incidence and fate of cases at shorter intervals were not taken into account. Thus, the information on incidence of pulmonary tuberculosis in India is meager as compared to that on prevalence of disease. Therefore, a study mainly to find out the incidence and fate of cases at shorter intervals of 3-6 months was undertaken in 87 randomly selected villages of Nelamangala sub-division, Bangalore district which was one of the 3 sub-divisions where repeated epidemiological surveys had been conducted between 1961-68. The sample of villages in the present investigation was other than that included in the earlier report. Organized Case-finding, anti-tuberculosis treatment and BCG vaccination neither existed nor could be provided in the area till the completion of the study. The present study was conducted between 1968-1972.

This study conducted among 30,576 persons has shown that incidence of cases over a period of three months was 0.99 per thousand and was not much different from the annual rate of 1.03 per thousand reported on the basis of repeated surveys at longer intervals. That the three months rates were not a quarter of the annual rates meant that the procedure of calculating incidence rates on the basis of surveys done at varying intervals after adjusting for the interval had to be used with great caution. The study of fate of cases showed that cases converted or reverted even at shorter intervals and this appeared to be going on continually in the community. However, incidence of cases and cure and death from among the existing as well as the fresh cases kept on balancing each other so that the prevalence rates of cases studied at shorter or at longer intervals did not show variations.

The entire population of a slum area of Bangalore city, comprising of 3313 persons was registered, questioned for symptoms and offered chest X-ray at a centre located in the slum itself. Those, who had any chest symptom and/or X-ray abnormality, were offered detailed examinations, viz., clinical examinations, repeated examinations of sputum for tubercle bacilli, and further chest X-rays. Of the total 2855 persons X-rayed and/or questioned, 1039 needed detailed examinations and about a fifth of the latter required referral to a consultant panel for diagnosis of chest diseases. Further, about 60% of those referred to consultants needed special investigations. Thus, the study of prevalence of chest diseases in the community needed considerable facilities and were operationally difficult. It is envisaged that similar problems will also be faced if peripheral dispensaries are to make proper diagnosis of chest diseases, due to the need for referral of large number of patients and provision of complicated diagnostic facilities at the referral hospitals. The study seeks to quantify the problem of chest diseases and tuberculosis in the slum community.

The prevalence of sickness in the population at any point of time were 49.5%. Sickness related to the respiratory system was 13.3%. It increased with age and was highest (42.6%) in those aged 55 years and above. Among 2855 persons X-rayed, 145(5.1%) had any radiological abnormality in chest. It is seen that respiratory systems symptoms were commonest in all the age groups. A total of 172 patients were diagnosed to have respiratory system abnormalities with or without X-ray lesions. Of them, 75% had non- tuberculous etiology, 7.6% had active pulmonary tuberculosis and the remaining 17.4% had inactive tuberculosis. Prevalence of sputum positive cases was 0.26% and prevalence of total active pulmonary tuberculosis was 0.44%. The problem of arriving at final diagnosis was dependent on application of complicated special investigation tools to a large community. In view of the low coverage (47.4%) for the special investigations, prevalence of different chest diseases in the community could not be investigated.

It is concluded that in the community under study, the size of the problem of non- tuberculous diseases of the chest and operational problems in their diagnosis were considerable.

A survey was carried out among 12,535 children in the age group 0-9 years of 90 villages in Doddballapur sub-division of Bangalore district to study the possible variation in the prevalence of tuberculous infection among the unvaccinated children in a village depending upon the varying prevalence of BCG scars in the same population. In each village, all the children in the age group of 0-9 years were registered and examined for the presence or absence of the BCG scar. Of the 12,535 children, 6269 (50%) who did not have BCG scars were eligible for tuberculin test, while 6045 were actually tested. Each child without BCG scar was tuberculin tested with 1 TU RT 23 with tween 80 and the reaction read between 72 and 96 hours. Two proportions were calculated in each village viz., a) the proportion with BCG scars and b) that of infected children among those without scar and the villages were distributed by these two proportions.

On the basis of distribution of tuberculin reactions, 10 and 12 mm induration was the demarcation between positive and negative reactors. Prevalence of infection among 0-9 years was 4.9%, 2.6% among 0-4 years and 8.9% among 5-9 years. Distribution of villages according to two variables i.e., prevalence of BCG scars and prevalence of infection among unvaccinated children did not show any correlation with the prevalence of infection among the unvaccinated in the same villages.

It is seen from the study that exclusions of various proportions of children with BCG scars did not have any correlation with the prevalence of infection among the unvaccinated in the same villages.

In non-e of the villages any association was seen between these two. In view of this finding, it is felt that the simple method of periodic tuberculin testing of the population in younger age groups could be developed into a method of tuberculosis surveillance even in areas where direct mass BCG vaccination is given. This would appear to be the cheapest, practicable and technically appropriate method of studying the overall tuberculosis situation.

Contact examination is not recommended as a routine procedure for Case-finding in the District Tuberculosis Programme. The rationale for not including contact examination as a routine Case-finding measure is: (1) prevalence rate of tuberculosis among the contacts is not much higher than in the general population (2) at the time of diagnosis of an index case, a second case may not be found in the same household. Though more prevalence cases cannot be diagnosed by contact examination, is it possible that by keeping the household contacts, as a group, under surveillance, future incidence of cases in the community can be substantially prevented? A model situation has been created by using hypothesis derived from various studies conducted in India, designed to answer the question. Variables used in the model are: 40% of the general population are infected at any point of time, there is only one prevalence case of TB at any given point of time in an average household of five, 40% of the non-infected population in a contact household are infected per year, incidence of disease among newly infected group is seven, times of the incidence among previously infected, incidence of disease in general population is 0.13% and from among previously infected persons 0.3% per year develop sputum disease.

At an incidence rate of 0.13% per year among general population aged >5 years, it is expected that 111 cases would arise in a year in the population of 1,00,000 under study. Thus, of the 111 cases occurring in the community, 101 arise from those who are not contacts.

The proportional contribution of new cases from the contact group to the total incidence cases in the entire community is so small, that even if all the contacts are kept under surveillance, BCG vaccinated or placed on chemoprophylaxis, still over 90% of incidence cases cannot be prevented from occurring. This is apart from the fact that keeping them under surveillance will be highly costly and is an operational problem of considerable magnitude.

The problem in using simple tools e.g. chest symptoms for epidemiological surveys, designed to quantify the problem is that estimates from these simple surveys are considerable underestimates. Recent research has, however, paved the way for the use of these simpler tools for use in estimating tuberculosis case prevalence rates in the community. A tool which is simple, convenient to use and maintain, cheap but highly sensitive is called "screening tool". Such tools are used for making initial selection of the given population. Tuberculin test, X-ray & symptom elicitation are the main screening tools used for epidemiological surveys and TB Control Programme. In the programme, symptom elicitation and X-ray examination are the screening tools of choice for Case-finding. In the survey, tuberculin and X-ray are the only two tools used, although tuberculin is not a good screening tool (40% population infected). Use of symptom screening in surveys, however, is restricted in the absence of adequate information on comparison of prevalence rates obtained by this method of screening with the best estimate. The performance of symptom screening with either culture or smear microscopy have been attempted. They showed that by applying suitable correction factors they may be rendered comparable to the best estimate. The symptoms may be useful in the survey as a screening tool and may give the rates as proximate to the true rates as possible. They will enable considerable simplification of epidemiological studies in tuberculosis without compromising on the precision of the estimates arrived at.

Prevalence of tuberculous infection in young children is an important surveillance measure. However, the hypersensitivity may be depressed by malnutrition and thus interfere with the interpretation of tuberculin test leading to underestimation of the infection rate. Objective of this investigation was to study the relationship between tuberculin reaction with 1 TU RT 23 and nutritional status of children. The study was carried out in 1974 among children aged 1-9 years of age living in an urban slum area of Bangalore city and who were not given BCG vaccination.

Of the 1151 registered children aged 0-9 years, 482 in the age group 1-4 and 526 in 5-9 years formed the study group. Of these 1008 children, 980 had both clinical evaluation and anthropometric measurement for nutritional status and 963 had both tuberculin test readings and anthropometric measurements carried out for them. Of the 482 children aged 1-4 years, 230 were classified as suffering from Protein Calorie Malnutrition (PCM) and of the 498 in the 5-9 years of age, 227 were classified as suffering from PCM. Distribution of tuberculin test indurations in mm among the normals and the undernourished were compared; no significant difference in the mean size of tuberculin indurations as well as in the distributions of these indurations was observed, regardless of the method used for arriving at the classification.

The trend of tuberculosis in a sample of 22 villages of Bangalore district observed over a period of about 16 years (1961-77) is reported. Distribution of tuberculin indurations did not show a clear cut demarcation between infected and non-infected. The method adopted to demarcate the cut off point has been described herewith: Distribution of tuberculin induration size of 0-14 years was attempted and extrapolated to higher age groups. Even in these younger age groups the antimodes were not clearly defined, so the antimode was arrived by fitting two normal curves as two likely modes.

The choice of demarcation level, therefore, is somewhat arbitrarily made on the basis of the distributions and these varied from survey to survey; between 10 mm at survey I and 16 mm at survey V. The actual and standardized infection rates showed more or less declining trend in 0-4 years, 5-9 years and 10-14 years age groups. The prevalence of cases was not significantly different from survey to survey (varying from 3.96 to 4.92 per thousand from first to fifth survey). However, there was a shift in the mean age of cases, and better survival rate of cases diagnosed at later surveys.

Material from a community survey carried out in rural areas of Karnataka by the National Tuberculosis Institute, Bangalore, has been analysed in an attempt to identify significant categories of the population that may yield higher proportion of cases. In all, 170 cases diagnosed among 61,581 persons have been distributed by their role, i.e., head of family (HOF) or not, kinship, (relationship to the HOF) by age and sex.

It has been observed that a comparatively small size of HOF male population (16.9%) would contain 55.9% of the total cases prevalent in the entire X-rayed population. On the other hand, the broad category other than HOF-male, would have case content relatively much less in proportion to their population size. Implications of the finding for house-to-house Case-finding by Multi-purpose Health Workers (HWs) are discussed here. It is possible to obtain higher case yield from the group having a higher case content which is aged 20 years and above and constitutes about 30% of the total population by confining to symptom screening. On the other hand, since cases are mostly in the HOF-males, would make it difficult for HWs to contact them in their normal visiting hours during day, as most of HOF-males may not be at home. Determined efforts have to be made by HWs to contact them during their beat schedule.

Distribution of tuberculin test indurations were studied in relation to nutritional status of 930 rural children aged 1-4 years and 796 aged 5-9 years. Using Quetlet's Index, it has been observed that the distribution of indurations were similar in normal and malnourished children. By following Jelliffe's criteria of grading nutrition, no correlation was observed between the size of induration and degree of malnutrition. It is concluded that malnutrition in the community may not influence the prevalence rates of tuberculin infection based on such testing.

A study was conducted in 1983-84 by the National TB Institute (NTI) in the districts of Dharmapuri (Tamil Nadu) & Ananthapur (Andhra Pradesh). Thirteen health personnel were trained in census taking, tuberculin testing & reading and data keeping etc., at the NTI according to the standard methodology. The trainees were repeatedly assessed and only those who achieved a reasonably high inter-reader correlation with the standard reader were chosen for the field work. Field work was carried out by these health workers and supervised by the team leaders of NTI. Children between 0-9 years were tested with 1 TU RT 23 with Tween 80 in tuberculin testing centres specially set up in each village and the reactions were read between 48 & 72 hours after the test. The tuberculin testing/reading coverage was very high. Of 6702 eligible children, 5904 (97%) were tuberculin test read.

Individual reading assessment carried out at Ananthapur and Dharmapuri for the State Field Workers (SFWs) showed that agreement with Standard Reader (SR) of NTI at three induration levels i.e., 10+ mm, 14+ mm and 18+ mm were very high. The demarcation line between infected and uninfected appeared to be about 18 mm. In Ananthapur, the agreement at 18+ mm was 99% and at Dharmapuri it was 100% for SFW, and 98.4% for SFW-2. The estimates of prevalence rate of infection were 9.3% - SFW V/s 9.7% - SR at Anantapur, 5.2% - SFW V/s 5.2% - SR and 7.2% - SFW.2 V/s 7.2% - SR at Dharmapuri. The study further showed that it was possible to train general health workers, within a period of 3 months to attain a high level of efficiency. The general health services can successfully organise on their own a programme of tuberculin testing in the community with proper liaison and supervision by some nodal agency. The training and field supervision responsibilities may be shouldered initially by NTI or another suitable organisation, till these nodal agencies come up.

The question of carrying out a repeat epidemiological survey in India has been engaging the attention of many for quite some time. The first nationwide tuberculosis prevalence survey was conducted in India during 1955-58. It served as an eye opener and produced data which were profitably used by the planners to decide about the form and state of national control programme. Doing a repeat survey will be useful only if it would be capable of yielding epidemiological information on the future course of action. At the time of formulation of the District Tuberculosis Programme (DTP), it was perhaps presumed that programme would work with optimum efficiency as in the operational studies and as such the real performance was not envisaged. Secondly, due to low prevalence rates of tuberculosis as shown in all the surveys could reflect a small rate of change or no change at all, thus these longitudinal surveys with inadequate samples, did not have enough discriminatory power to observe a statistically valid change with time.

It is now globally realised that instead of looking at mortality rates or small changes in the prevalence rates of cases, it is the Annual Risk of Infection (ARI) which holds the key to epidemiological trend in a community. However, through a model recently constructed at the National Tuberculosis Institute, it is possible to extrapolate the findings of well planned small surveys in certain areas. It gives an idea what to expect over a period of 50 years - a slow decline. Therefore, when the present efficiency of Case-finding programme is about 33%, treatment efficiency also of the same order or even worse and with persistent rise in the population, it is futile to talk of epidemiological assessment through repeat surveys. Instead, we should concentrate on raising the efficiency of the DTP as near to the level which could be called the critical level of efficiency. Till then nation wide surveillance through the calculation of ARI is the only choice.

In a chronic disease like tuberculosis, the exact levels of prevalence or incidence of infection and disease are of lesser importance than its time trend. Surveys should be conducted repeatedly if possible, in order to study the latter. Longitudinal surveys, conducted by National Tuberculosis Institute (NTI) & New Delhi TB Centre, could provide information only on the incidence and prevalence of the disease & infection and not on the time trend due to inadequate sample size of the population selected for the surveys. To measure an annual decline of 1% after 12 years, NTI should have taken a population of 4,45,000 for Tumkur survey instead of 35,000 actually taken. An attempt to measure the trend with the help of epidemetric model also suffers from the inherent infirmity of the small population size. It gave little statistical support to the coefficient of variations of the observed rates, thus imparting little discriminatory power to the observed rates. The error of taking inadequate sample size of the population for these surveys, could be attributed to: (1) The statistical concept of epidemiological assessment through repeated measurement of TB problem had not yet concretised in the minds of the Epidemiologists and Programme Planners. (2) A very high rate of decline was expected after the implementation of the District TB Programme (DTP). (3) The purpose of longitudinal surveys was to get information only on the incidence of infection & disease and not to measure the change. (4) It was not envisaged in 1962 when DTP was being formulated, that there would be no change situation in the prevalence rate of tuberculosis after implementation of DTP from that found in National Sample Survey carried out during 1955-58. The hypothesis underlying static situation was formulated by the Indian epidemiologists later taking their clue from Grigg's momentous work.

Mean time it was established that the Annual Risk of Infection (ARI) holds the key for evaluating the epidemiological trend in a community. From the available data from Longitudinal Survey of NTI it has been found that almost identical rates of ARI were calculated as incidence rates of infection actually observed during the initial surveys. Over a period of 23 years, there has been an annual decline in the risk of infection for the area at the rate of 3.2%. Estimation of incidence of smear positive cases on the basis of the ARI could be made (1% ARI being equivalent of 50 cases per 100,000 population). The findings commensurate with observations made 23 years later, wherein incidence of cases was observed 23/100,000 population and ARI of 0.6% (a parametric relationship seen). The programme operation of average 33% efficiency for nearly three decades would give an annual declining trend of the following extent: 1.4% in case rate, 2.0% in smear positive case rate and 3.2% in ARI. Alternatively the above trend could also represent the natural dynamics.

Screening of the population by Mass Miniature Radiography (MMR) followed by sputum examination by culture of the X-ray abnormals is the customary method for arriving at the prevalence rate of cases in the community. It is not possible to use this methodology by states to carry out prevalence surveys in these areas, even if they desire to evaluate the effect of anti tuberculosis measures implemented by them. Therefore, simpler means of screening population through chest symptom for sputum examination has been studied by National Tuberculosis Institute (NTI). The objectives of the present investigation were to find out the prevalence of bacillary cases by screening the population through identification of chest symptomatics by Social Investigators (Sls) or General Health Workers (GHWs) compared to that by MMR. In a peri urban area 10 kms away and around Bangalore city all the villages were listed and of the 60 villages were selected on the basis of a sample random sample. Of them, 30 were covered by Sls of NTI and the other 30 by GHWs of the state government. The methodology adopted was that (1) After census taking and registration of the entire population aged 15 years and above, Sls questioned the persons house to house for presence of cardinal chest symptoms of any duration. All chest symptomatics were subjected to MMR and sputum examination. (2) Similar methodology was adopted by GHWs in the other 30 villages allotted to them. (3) Without knowing the symptom status of all the registered persons, aged 15 years and more belonging to all the 60 villages, were subjected to MMR and from among those having X-ray abnormalities, to sputum examination.

It was found that GHWs had identified the same proportion of the persons either having general symptoms or having chest symptoms from the general population, as Sls. Prevalence rates of culture positive as well as smear positive cases were similar by any of the three methods i.e., 0.18%, 0.23% & 0.25% respectively. Prevalence rates of smear positive cases obtained through symptom questioning, either by Sls or GHWs, were more or less similar to the estimates obtained by the more comprehensive screening method of MMR and/or symptom questioning. The culture positive prevalence rate following MMR screening was 0.25%, which was lower than the rates observed in other surveys. The paper discusses the possible hypothesis that could explain the observation. It also presents correction factors to compute rates comparable to the best estimate i.e., that obtained through comprehensive screening by MMR and/or symptom questioning, followed by sputum culture.

Mass miniature radiography (MMR) is the usual tool for population screening in tuberculosis case prevalence surveys. However, this facility is not available at most centres in India. An attempt was made to study the feasibility of carrying out sputum positive case prevalence survey in a population by introducing methodological variation in the screening, in order to select those eligible for sputum test without resorting to the customary use of MMR for the purpose. The study was carried out in Bangalore rural district during 1984-1986. The area was the same as for six earlier prevalence surveys conducted since 1961. The population aged up to 44 years was tuberculin tested. Persons with test induration size of = 10 mm were eligible for sputum examination, besides all those aged over 45 years were eligible. It was observed that 78.4% of the registered population (29400) in the age group 10 years and above were required to undergo sputum examination by the present method of screening leading to a very high work load of sputum examination necessitating deployment of additional sputum cultures. Thus, the purpose of pre selection for sputum examination was hardly fulfilled. Further, a high contamination rate was observed. The changed screening procedure in this survey made comparison with the earlier data difficult.

The overall prevalence rate of cases was 438/100,000 in persons aged 10 years and above, while smear positive prevalence rate was 68/100,000. The observed prevalence rate was similar to earlier surveys, while smear positive prevalence rate was much lower. In conclusion, the screening methodology was found to be operationally unfeasible, ineffective and counterproductive to complicate the survey procedure in the quest for simplicity.

At present, Case-finding activity of tuberculosis through the self reporting chest symptomatics attending Peripheral Health Institutions, is at a low ebb. With the introduction of Multi Purpose Workers (MPW) scheme, a machinery has emerged through which this activity could be augmented. An operational study was therefore undertaken in five Primary Health Centres (PHCs) of Chittoor district, Andhra Pradesh in June 1978.

The study has revealed that if the MPWs collect sputum smears from the symptomatics of the age group of 20 years and above during their routine visits to each household of the specified population allotted to them and despatch the smears to the PHC for examination, there is a possibility of augmenting the existing Case-finding activity by 4 5 times. An intensive training of 2 3 days for this purpose seems adequate. The average work load for a MPW would be preparation of one smear a day initially for a couple of months and thereafter as a routine one smear a week. In an average PHC, the work load for the microscopist would be to examine 10 to 12 slides a day initially, the load will then progressively decline and subsequently as a routine it will not be more than 3 4 slides a day. An additional microscopist would probably be needed at PHC laboratory for examination of sputum smears as well as to assist the existing microscopist who at present is primarily engaged in malaria work. Meticulous supervision and regular flow of supplies and equipment is however a 'must' for the success of the scheme.

The results of the tuberculosis prevalence surveys carried out in 59 villages of Tumkur district, Karnataka in 196l before launching the District Tuberculosis Control Programme (1964) and the second one, nine years after the introduction of the programme (1973), were compared.

The prevalence rates in both the surveys were similar viz. 0.41 per cent in 1961 and 0.44 per cent in 1973 indicating the poor impact of the programme. The present analysis provides information on long term cumulative performance of the District Tuberculosis Programme (DTP) in diagnosing the cases detected in a prevalence survey at a point of time. Of the 70 cases diagnosed during I survey 12 (17.1%), and of 121 during II survey 20 (16.5%) were diagnosed by the District TB Programme independently over a total period of 19 years. Of the 12 DTP cases of I survey, 1/3rd were diagnosed by DTP within 3 years and the remaining were distributed over a period of 12 years. Similarly, of the 20 cases of II survey, 45% were found within 3 years after the survey and 25% within 3 year periods immediately prior to it. In subsequent years, Case-finding activity about these prevalence cases was erratic and at much lower rate. There was no difference between smear positive and culture positive survey cases with respect to their diagnosis by DTP. The changes brought about in the prevalence of cases from year to year by death, cure, incidence and performance of DTP, in diagnosing such prevalence cases, could not be studied from the available material. Under reporting of the diagnosed cases and missed diagnosis are attributed to be the main factors for poor performance of the DTP.

Potentials of Case-finding and case holding through operational studies conducted by National TB Institute (NTI) and elsewhere have been quantified. The potential of case holding is not satisfactory and needs revision of strategy to obtain better treatment completion. The present report reviews the programme in its ability to meet the potential in Case-finding and treatment (CFT), and bring about a reduction in the problem. Outcome at the current levels of efficiency of activities as well as following hypothetical changes in them, are studied. Further it identifies the areas for carrying out studies on structural changes to be introduced in the programme, so as to obtain higher results in terms of epidemiological gains.

A set of hypothesis which have been used in constructing the model are based on the currently available information on the epidemiology of tuberculosis and performance of the programme. An average Indian district as per 1991 census is considered to have: (a) a population of 1.9 million; (b) 6460 smear and culture positive patients (prevalence rate of 4 per thousand) in all at any time; (b1) 2584 of the prevalence cases are smear positive; (b2) 2196 newly occurring cases every year (annual incidence of 34% of prevalence); (b3) 879 of the b1 being the annual incidence of smear positive cases; (c) 3230 of the prevalence cases who present themselves for diagnosis (50% of b); (d) 2584 can be diagnosed if all the available PHIs participate in the programme as per the manual. This is called Case-finding potential (CFP). The Case-finding Efficiency (CFE) is expressed as a proportion of the cases being diagnosed out of the CFP by a DTP. The current CFE is calculated at 36% of CFP, as 936 cases are being diagnosed (as per the periodic DTP reports prepared by NTI). The result of treatment at the current treatment efficiency TE1 for the cases on Standard Regimen (SR) (Compliance 45% at level 4) is 50%, TE2 for those on SCC (compliance 56% at level 4) is 79%, TE3 WHO recommended 85% cure rate (compliance level and regimen not stated). DTP efficiency (DTPE) is the proportion of cases which could be cured with the respective TE, calculated out of the CFP. DTPE under SR l8%, under SCC is 28.44%.

Epidemiological impact is calculated while taking into consideration the natural dynamics of tuberculosis without intervention and the dynamics of the programme where the cases are diagnosed and treated with SR under the current efficiency, the same is computed for the patients treated with SCC with present level of efficiency. The cure and death rates among treated cases is added to the natural cure without a programme (Case fatality rate of 14% and cure rate of 20% is equal to 34% of incidence rate which keeps the prevalence rate unchanged in natural dynamics). With all the cases treated with SR, programme appears to show a problem reduction of 4.6% annually and with SCC of 6.5%. The latter shows a relative benefit of 41% over the former besides causing prevention of deaths at the end of treatment.

 Addl decline alternative in question
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               Relative Benefit

Decline with 36% CFE & on SR with 45% compliance level IV

Intervention alternatives with fixed CFE by raising compliance level 4 from 45% to two higher levels to 70% and 90%, are studied. They give an additional decline of 2.1% and 3.0% respectively. While raising compliance level 4 of patients on SCC from current 56% to 70% and 90%, the additional decline is marginal (2.6% & 2.9%). At the same time raising the compliance to the level 4 is not only operationally a difficult task but does not commensurate with epidemiological gains also.

Intervention Alternative Recommended by WHO : To further epidemiological gains, it is obvious that CFE also needs to be raised. The WHO has recommended the target of CFE as 70% of all smear positive cases, TE as 85%. For this alternative, DTPE is 59.5%; epidemiological gain 13.7%, additional decline 9.5% on SR with 45% compliance level and relative benefit of 206.5%. This alternative appears to be feasible provided coverage of implementation of PHIs and treatment compliance are high and use of SCC regimens in the programme are ensuring for such achievements.

Operational Alternatives on Improving Treatment Compliance To improve treatment compliance level it is essential that patients are treated free, get supply of drugs regularly as near to their homes as possible and may be given supervised treatment specially in the intensive phase. Recent development of infrastructure makes it possible to consider alternatives to ensure the supply of drugs close to patients residence. Some of the health functionaries below the level of PHIs are: Health Worker (HW) Anganwadi Worker, Dai (Traditional Birth Attender), Community Health Volunteers (CHV) and Private Practitioner. The possibility of involving them in some or other manner in tuberculosis treatment activity under a programme may be explored.