EPIDEMIOLOGY <<Back
 
 
002
SIZE & EXTENT OF TB PROBLEM IN URBAN & RURAL INDIA
Raj Narain: Indian J TB 1962, 9, 147-50 & also in Proceed Natl TB & Chest Dis Workers Conf 1962, 155-68.

The aim of modern Public Health Programmes, is a reduction in the total amount of disease in the community. The unit for treatment and cure is not an individual but a sick community. With this new aim, it becomes essential to know the size and extent of tuberculosis in the community as it will be helpful not for purposes of planning only but essentially for the assessment of their effect on the problem. An attempt is made to review the important features of the available knowledge about infection, morbidity and mortality through various surveys. (i) Prevalence of Infection: Tuberculosis infection is widespread in both urban and rural areas of almost all parts of the country. Nearly 40% of the population are infected. To avoid the effect of non- specific allergy and get a more reliable demarcation, tuberculin reactions of 14mm and more were considered as positive by National Tuberculosis Institute. (ii) Prevalence of morbidity: The prevalence of radiologically active tuberculosis in the population is likely to be 1.5%, Prevalence of bacteriologically confirmed diseases is 0.4%. Based on single sample of sputum examination, the prevalence of infectious cases in the country is probably an under estimate. About two million are infectious at any one point of time. (iii) Mortality: Deaths from tuberculosis in the country is not definitely known. The impression of clinicians that death due to tuberculosis have fallen sharply may not be true. Half a million deaths will appear an underestimate. About 250 per 1,00,000 persons i.e., one million deaths due to tuberculosis per year seems to be a reasonable estimate. (iv) Bovine Tuberculosis: Only a few cases in man caused by the bovine tubercle bacillus have been reported although 2.75% to 25% of cattle have been found tuberculin reactors.

To put in a nut shell, the problem of tuberculosis in India is a gigantic one and our means of fighting it with the single tool of BCG, do not even touch the fringe of the problem.

KEY WORDS: INFECTION, SUSPECT CASE, CASE, MORTALITY, COMMUNITY.

006
SOME ASPECTS OF A TB PREVALENCE SURVEY IN A SOUTH INDIAN DISTRICT
Raj Narain, A Geser, MV Jambunathan & M Subramanian: Bull WHO 1963, 29, 641-64 & Indian J TB 1963, 9, 85-116.

The objective was to establish the prevalence rates for tuberculosis infection, radiologically active pulmonary tuberculosis and bacteriologically confirmed diseases for different age and sex groups. Tumkur District in Mysore State consisting of 2,392 villages, 10 towns of was selected for the study. The district headquarter town Tumkur was excluded from the survey. Random sample of 62 villages and 4 town blocks having a population of 34,746 persons constituted the study population. All the individuals available in the registered population were given a Mantoux test with 1 TU RT 23 with Tween 80. Longitudinal diameter of induration was read 3-4 days after the test. At the time of tuberculin test, all persons aged 10 years and above were offered a single 70mm photofluorogram. For each picture read as abnormal, a spot specimen of sputum of the individual concerned was collected at the time of reading the tuberculin test. Age and sex distribution of infection and disease were studied.

Various parameters concerning the prevalence of infection and disease in the community were reported. Prevalence rate of infection in all ages and both sexes of the population was found to be 38.3%, radiologically active tuberculosis 1.86% and 0.41% sputum positive disease. The infection and disease increased with age; of the total diseased, half were in age group 40 years and more and about 2/3 among males.

KEY WORDS: SURVEY, PREVALENCE, INFECTION, DISEASE, CASE, COMMIUNITY, RURAL, URBAN.

011
FATE OF CASES DIAGNOSED IN A SURVEY
Raj Narain, G Ramanatha Rao, G Chandrasekhar & Pyare Lal: Proceed Natl TB & Chest Dis Workers’ Conf, Calcutta, 1966,72-78.

The report describes the changes that occurred during second survey carried out after an interval of one and half years in the cases diagnosed at the first survey done during 1961-62 from among a total population of about 62,000 in 119 villages in Bangalore District. It was observed that (1) Of the 62 sputum smear positive cases also having suggestive chest X-ray shadows, 34% had died, 35% were sputum positive and 31% had become culture negative after 1½ years. Of the 10 smear positive cases who were X-ray normal, non-e was culture positive at the start and 7 were negative by culture and smear after 1½ years. Of the 67 scanty smear positive cases (1 to 3 bacilli seen), only 3 were sputum positive, 10 were having X-ray shadows and half were tuberculin negative after 1½ years. (2) Of the 88 culture only positive cases (20 or more colonies and with X-ray evidence of disease) 31% had died and 47% continued to be sputum positive after 1½ years. A much smaller proportion of these changes occurred among culture positive cases with less than 20 colonies. (3) There were 457 persons having radiologically active tuberculosis on the basis of interpretation of a single X-ray picture by two independent readers but whose sputum were negative for AFB (suspect cases). Of these, 38% were tuberculin negative also. Of those suspect cases who were tuberculin positive, 9% become sputum positive after 1½ years, while only 2% of the tuberculin negative suspect cases became sputum positive.

It is concluded that there is a lot of variation in fate among the different categories of cases of pulmonary tuberculosis. Further, attention has been drawn to the possibility of self healing in about 30% of the bacillary cases after 1½ years.

KEY WORDS: FATE, CASE, SUSPECT CASE, NATURAL CURE, PREVALENCE.

012
PREVALENCE, FATE, SOURCE AND INFECTIVITY OF RESISTANT IN MYCOBACTERIUM TUBERCULOSIS
Raj Narain, P Chandrasekhar, Pyare Lal and RA Satyanarayanachar: Proceed Natl TB & Chest Dis Workers’ Conf, Hyderabad, 1967, 37-51.

The material on resistant strains of mycobacterium tuberculosis is derived from the longitudinal survey conducted from 1961-68 in a random sample of 133 villages of 3 taluks of Bangalore district. About 54,000 persons aged five years or more were surveyed 3 times at an interval of 18 months, two samples of sputum were collected from persons whose chest X-rays were judged to have abnormal shadows. The sputum specimens were examined by direct smear and culture and sensitivity tests were performed.

An attempt is made to study prevalence, fate, source and infectivity of resistant mycobacterium tuberculosis in three rounds. PREVALENCE: In the 3 rounds, 199, 194 and 176 cases respectively yielded positive cultures; Of them, 30, 36 and 53 cases were having resistant strains. At round III, the number of culture positive cases has not fallen significantly, but the number of strains resistant to INH alone has sharply increased (13, 18 & 35). Both findings are likely to be due to the treatment with INH alone offered at round II and also due to the fact that treatment was taken very irregularly. FATE: Over period of 3 years, of the cases with INH resistant strains, more than 1/3rd were dead, 1/4th continued to remain positive and resistant, and 1/4th became culture negative. Whereas, of the cases with strains sensitive to INH, less than 1/3rd were dead, 1/3rd became negative and the remaining were positive, 1/2 with sensitive strains and 1/2 with resistant strains. SOURCE OF CASES: The prevalence of cases with resistant strains at any one round is not due to the persistence of such cases from previous rounds but by development of new cases with such strains at each round. INFECTIVITY: The incidence of infection among contacts with sensitive strain was significantly more than among the contacts of cases with resistant strain. It is inferred that the infectivity of sensitive strains is more than that of the resistant strains.

KEY WORDS: M.TUBERCULOSIS, SENSITIVE STRAINS, RESISTANT STRAINS, CASE, FATE, PREVALENCE, INFECTIVITY.

017
DISTRIBUTION OF TUBERCULOUS INFECTION AND DISEASE IN CLUSTERS OF RURAL HOUSEHOLDS
SS Nair, G Ramanatha Rao & P Chandrasekhar: Indian J TB 1971, 18, 3-9.

Data from 62 randomly selected villages in a district of south India, which formed part of a prevalence survey carried out by the National Tuberculosis Institute, Bangalore, during 1960-61, has been made use of. The survey covered 29,813 persons in 5,266 households. There were 70 cases with bacilli demonstrable either in smear or culture and 300 suspect cases. Using the village map (prepared by survey staff), ‘case clusters’ were formed first, with each case household as nucleus and adjacent households within a maximum distance of about 20 meters on either side of the case households. Households closest to the nucleus household on either side have been called as 1st neighbourhood and those coming next in proximity on either side as a 2nd neighbourhood and so on. The case household and its four neighbourhood together was called a cluster. If another case household was found within 4th neighbourhood of the first case the cluster was extended by including the 4th neighbourhood of the new case also. Such clusters were called composite case clusters and clusters with only one case household as simple case clusters. Similarly, suspect case clusters were formed and differentiated as simple suspect clusters or composite suspect clusters. Further, to serve as a control group, non-case clusters were constituted from a systematic sample of 10% households that were not included in case or suspect case clusters.

Out of 60 case clusters formed, only 7 have multiple cases showing that there was no evidence of high concentration of disease in case clusters. While the percentage of child contacts (0-14 years) infected was considerably higher in case clusters (25.8%), there was not much difference between suspect case clusters (14.9%) and non-case clusters (9.8%). Similarly, there was not much difference between simple and composite clusters. Infection among child contacts was higher in case households as compared to their neighbourhoods. To get some idea of the zone of influence of a case or suspect case, prevalence of infection was studied for 10 neighbourhoods, in simple clusters to avoid the influence of multiple cases. It appeared that the zone of influence of a case may extend at least upto the 10th neighbourhood. It was also noted that there was very little difference between zones of influence of suspect cases and non-cases. Case clusters in which the nucleus case had shown activity of lung lesion (evident on X-ray reading) or had cough showed significantly higher infection among child contacts. Clusters around cases positive on both smear and culture did not show higher infection than those around cases positive on culture only. (This may be due to sputum examination of single specimen only).

Out of the total infected persons in the community, only 2% were in case households and 7% in suspect case households, over 90% being in non-case households. The zone of influence of a case extending at least upto the 10th neighbourhood and the overlapping of such zones of influence of cases, present and past, seems to be the most probable explanation for the wide scatter of infection in the community. Prevalence of infection among child contacts was definitely higher in case clusters. But, the significance of this could be understood only from a study of the incidence of disease during subsequent years in different types of clusters. It is significant that only 10% of the total infected persons in the community were found in case clusters. The case yield in general population, cluster contacts, household contacts and symptomatics attending general health institutions have been also compared. The case yield in the last group (10%) is much higher than the case yield from both types of contacts (0.7% and 0.6%) which where only slightly higher than the case yield from the general population (0.4%).

KEYWORDS: RURAL, HOUSEHOLDS, CLUSTERS, CASE, SUSPECT CASE, CONTACT, PREVALENCE, INFECTION, DISEASE, SURVEY.

019
SOME ASPECTS OF CHANGES IN RURAL POPULATION AND FATE OF TB CASES AFTER AN INTERVAL OF TWELVE YEARS
MS Krishnamurthy, KR Rangaswamy, AN Shashidhara & GC Banerjee: NTI Newsletter, 1974, 11, 1-7.

During second epidemiological survey carried out in 1972-73, special efforts were made in 21 of 62 villages belonging to first survey (1961-62) to study the demographic changes and fate of TB cases after an interval of 12 years.

The findings were: The increase of dejure population was about 20% over a period of 12 years i.e., an annual increase of 1.7%. The age structure had altered mainly due to significant increase in the age group 60 years and above – 51% to 64% indicating aging of population. The loss of original population after 12 years was 44%, of which 33% was due to migration and 11% due to death. The overall migration was more among females. The migration rate was higher in younger age group, being highest in 10-19 years (49%), next in 0-9 years (38%). Thus, overall migration in 0-19 years was 43%. The death rate was highest in 60 years and above (58%). It varied from 4-9% in age group 0-39 years. Original population available after 12 years for re-examination was 56%. Distribution in different age groups were; 0-9yr = 57%, 10-19yrs = 47%, 20-49yrs = 66%, 50-59yrs = 44%, 60yrs and more = 28%.

Out of 88 X-ray suspect cases of earlier survey, 87 could be identified and present status of 72 were known. Of them, 16 were normal, 12 and 4 found to be suspect cases and bacillary cases respectively and 40 had died. Of the remaining fifteen, 11 migrated and 4 not examined. Out of 14 bacillary cases, 13 could be identified. Of them, 3 were sputum negatives (2 normal and 1 suspect case) 9 had died and 1 migrated.

KEYWORDS: FATE, CASE, SUSPECT CASE, MORTALITY, MIGRATION, RURAL POPULATION, DEMOGRAPHIC CHANGES, SURVEY.

024
ESTIMATION OF NUMBER OF REPEAT EXAMINATIONS REQUIRED TO DETECT ALL TB CASES IN THE COMMUNITY
R Rajalakshmi & SS Nair: Indian J Public Health 1976, 20, 118-21.

Examination of only one sputum sample cannot detect all the sputum positive cases in the community. To obtain better estimates of the prevalence of bacteriologically confirmed disease in the community, a study was conducted to find out the additional yield of cases through collection and examination of eight sputum specimens and also in order to work out correction factors for estimates based on one or two sputum samples, as collecting multiple sputa is very difficult. The study was carried out in 77 villages in Nelamangala Taluk of Bangalore. In all, 5826 persons were referred for sputum examinations.

Results of all the eight culture examinations were available for 2973 (51% of the eligibles). Of these 64 persons were positive by culture of atleast one specimen. Each of the eight specimens has the chance of detecting a case and any one of them could be considered as first or second specimen etc. To overcome this difficulty 80 permutations were randomly chosen out of the total 40,320 permutations possible. Cases from first specimen and additional cases from subsequent specimens were calculated through four mathematical equations. The first equation namely Y = KXm (28.66 x-1.40) has been considered as providing the best fit to the observed data. On the basis of this equation it appears that additional positives could be obtained upto the 1Oth specimen. Out of 64 culture positive cases, only 72% of positives could be detected by first two samples. To get about 95% of the cases, it is necessary to examine at least six specimens from each individual. Multiple samples are rewarding for detecting even high grade cultures.

KEY WORDS: MULTIPLE SPUTUM SPECIMEN, SPUTUM EXAMINATION, CASE YIELD, PREVALENCE, CASE, SURVEY.

025
PRECISION OF ESTIMATES OF PREVALENCE OF BACTERIOLOGICALLY CONFIRMED PULMONARY TUBERCULOSIS IN GENERAL POPULATION
SS Nair, GD Gothi, N Naganathan, K Padmanabha Rao, GC Banerjee & R Rajalakshmi: Indian J TB 1976, 23, 152-59.

This paper reports on a study conducted in the year 1975 to estimate yield of tuberculosis cases from multiple sputum specimens, and work out correction factors to be applied to estimates based on small number of specimens. Eight sputum specimens were collected within a fortnight from each person with an abnormal chest X-ray during an epidemiological survey in 77 villages in a district of south India. Each specimen was examined by Ziehl-Neelsen technique of microscopy and culture. In all, 3,199 persons were referred for sputum examination and results of all the eight specimens were available for 1,652. Of the latter, 64 were culture positive.

The first specimen detected 58% of the culture positives and the additional positives by later specimens generally decreased. The contribution from the first specimen was 71% for cultures showing good growth and 19% for cultures with scanty growth. Similarly for positives on both culture and microscopy, first specimen detected 87% whereas the corresponding proportion was 32% for those positive only on culture. The type of specimen (viz., spot or overnight) and age or sex of the case did not influence the yield from multiple examinations. The precision of an estimate of prevalence will depend on the number of specimens on which it is based and the coverage obtained in the collection and examination of specimens. Correction factors to be applied to such estimates based on one or two specimens, for various levels of coverage have been presented. For example, an estimate of prevalence based on one sputum specimen with 90% coverage will have to be nearly doubled to get a more precise estimate. Using these correction factors, revised estimates of prevalence have been presented for a number of prevalence surveys conducted in India. It has been estimated that the total number of infectious cases in India at present may be at least 3 million, as against 2 million according to earlier estimates.

KEY WORDS: PREVALENCE, CASE, RURAL POPULATION, MULTIPLE SPUTUM SPECIMEN, ESTIMATES, SPUTUM EXAMINATION.

026
INCIDENCE OF TUBERCULOSIS AMONG NEWLY INFECTED POPULATION AND IN RELATION TO THE DURATION OF INFECTED STATUS
VV Krishnamurthy, SS Nair, GD Gothi & AK Chakraborty: Indian J TB 1976, 23, 3-7.

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.

KEY WORDS: INCIDENCE, INFECTION, CASE, TUBERCULIN STATUS.

027
RELAPSE AMONG NATURALLY CURED CASES OF PULMONARY TUBERCULOSIS
AK Chakraborty & GD Gothi: Indian J TB 1976, 23, 8-13.

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.

KEY WORDS: RELAPSE, NATURAL CURE, CASE, RURAL POPULATION, SURVEY.

030
ESTIMATION OF PREVALENCE OF BACILLARY TUBERCULOSIS ON THE BASIS OF CHEST X-RAY AND/OR SYMPTOMATIC SCREENING
GD Gothi, Radha Narayan, SS Nair, AK Chakraborty & N Srikantaramu: Indian J Med Res 1976, 64, 1150-59.

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.

KEY WORDS: PREVALENCE, CASE, SYMPTOM SCREENING, X-RAY EXAMINATION, RURAL COMMUNITY.

038
A COMPARISON OF NEW CASES (INCIDENCE CASES) WHO HAD COME FROM DIFFERENT EPIDEMIOLOGICAL GROUPS IN THE POPULATION
VV Krishnamurthy, SS Nair & GD Gothi: Indian J TB 1978, 25, 144-46.

In a five year epidemiological survey conducted by National Tuberculosis Institute (NTI) from 1961 to 1968, the population was mainly classified into three epidemiological groups (i) with no radiological abnormalities seen in the lungs (Group N) (ii) having X-ray shadows of non-tuberculous etiology or tuberculosis etiology but judged as inactive (Group M) and (iii) with shadows of tuberculosis etiology judged possibly or definitely active but negative on culture (Group S). The objective of this paper is to compare the characteristics of cases coming from the above three groups (N, M and S) in respect to bacillary disease status (a) at the time of diagnosis and (b) after a lapse of time (Fate). Out of the total 172 new cases diagnosed during three follow ups, 70 were diagnosed between I & II surveys, 40 between II and III and 62 between III-IV surveys. In the two 18 months follow up periods, 45 of the total new cases had come from Group N, 31 cases from Group M and 34 cases from Group S, corresponding figures for 24 months follow up (III & IV surveys) were 26, 26 and 10 respectively.

In the 18 months follow up it was observed that proportion of new cases positive on culture in the three groups were not significantly different. Comparison of fate of cases coming from three groups were similar in terms of cure, death and culture positivity. The findings point out clearly that not only development of disease but also the fate of cases is independent of pre diagnosis status of the new cases.

From all the 3 groups, disease developed more rapidly in some cases than in others. This reveals that tuberculosis cases are not an uniform entity from the point of view of development of the disease and cure.

KEY WORDS: INCIDENCE, CASE, EPIDEMIOLOGICAL GROUPS, RURAL POPULATION.

040
INCIDENCE OF PULMONARY TUBERCULOSIS AND CHANGE IN BACTERIOLOGICAL STATUS OF CASES AT SHORTER INTERVALS
GD Gothi, AK Chakraborty, K Parthasarathy & VV Krishnamurthy: Indian J Med Res 1978, 68, 564-74.

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.

KEY WORDS: INCIDENCE, FATE, CASE, RURAL POPULATION, SURVEY, SHORTER INTERVALS

041
CHEST DISEASES AND TUBERCULOSIS IN A SLUM COMMUNITY AND PROBLEMS IN ESTIMATING THEIR PREVALENCE
AK Chakraborty, GD Gothi, Benjamin Issac, KR Rangaswamy, MS Krishnamurthy & R Rajalakshmi: Indian J Public Health 1979, 23, 88-99.

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.

KEY WORDS: PREVALENCE, URBAN, SLUM COMMUNITY, CHEST DISEASES, CASE.

044
INCIDENCE OF TUBERCULOSIS CASES IN CONTACTS - A SIMPLE MODEL
AK Chakraborty, Hardan Singh & P Jagota: Indian J Prev & Soc Med 1980, 11, 108-11.

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.

KEY WORDS: INCIDENCE, CASE, CONTACTS, MODEL

047
MORTALITY AND CASE FATALITY OF TUBERCULOSIS CASES DIAGNOSED IN A RURAL POPULATION OF SOUTH INDIA
VV Krishna Murthy: NTI Newsletter 1982, 19, 8-13.

Mortality from tuberculosis is an important epidemiological parameter for defining the problem of tuberculosis in any country. But due to lack of systematic recording and reporting system, precise information on cause of death is not available in our country. An attempt has been made to estimate the case fatality of tuberculosis cases as well as mortality of cases diagnosed in a longitudinal study conducted from 1961-68 in Bangalore district. Crude mortality of cases is defined as the ratio of total deaths observed among cases to the total number of cases observed, while case fatality is defined as the ratio of deaths that have occurred due to tuberculosis to the total number of cases investigated.

The overall observed annual crude mortality was 14.8%, while among culture positive smear positive (C+S+) it was 21%. An upward trend was seen with the increase in the age. The overall annual crude mortality among culture positive smear negative (C+S-) cases was 9.5% which is significantly lower than that among C+S+ cases. The death rates among old and new cases at the end of 18 months were 16.7% and 13.7% respectively. No statistical difference was found in the crude mortality either among old and new cases or in relation to the interval of diagnosis. Case fatality due to tuberculosis was computed by calculating the deaths among non-tuberculosis population of the same area and during same period and eliminated from the total deaths observed among tuberculosis cases. The case fatality of tuberculosis was found to be 13.3%. It was further observed that out of the total 38 deaths among cases, 89% were due to tuberculosis and 11% were due to non-tuberculosis causes.

KEY WORDS: MORTALITY, CASE FATALITY, CASE, RURAL POPULATION, SURVEY.

049
TUBERCULOSIS IN A RURAL POPULATION OF SOUTH INDIA: REPORT ON FIVE SURVEYS
AK Chakraborty, Hardan Singh, K Srikantan, KR Rangaswamy, MS Krishnamurthy & JA Steaphen: Indian J TB 1982, 29, 153-67.

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.

KEY WORDS: TREND, CASE, INFECTION, PREVALENCE, TUBERCULIN READING METHOD, LONGITUDINAL SURVEY.

051
DISTRIBUTION OF TUBERCULOSIS CASES AMONG FAMIILY RELATIONS IN A RURAL COMMUNITY
R Channabasavaiah & AK Chakraborty: NTI Newsletter 1984, 20, 63-72.

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.

KEY WORDS: CASE, FAMILY, RURAL COMMUNITY.

063
PREVALENCE OF PULMONARY TUBERCULOSIS IN A PERI-URBAN COMMUNITY OF BANGALORE UNDER VARIOUS METHODS OF POPULATION SCREENING
AK Chakraborty, R Channabasavaiah, MS Krishna Murthy, AN Shashidhara, VV Krishna Murthy & K Chaudhuri: Indian J TB 1994, 41, 17-27.

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.

KEY WORDS: SCREENING TOOLS, CHEST SYMPTOMATICS, MMR, PREVALENCE, CASE, PERI URBAN COMMUNITY.
 

 
  OPERATIONS RESEARCH  
 
A : Problem Definition
 
076
A SOCIOLOGICAL STUDY OF THE AWARENESS OF SYMPTOMS SUGGESTIVE OF PULMO NARY TUBERCULOSIS
D Banerji & Stig Andersen: Bull WHO 1963, 29, 665-83

This study was undertaken in 34 villages and 4 town blocks where a few weeks earlier an epidemiological survey was carried out. All persons above 20 years whose photofluorograms were read as inactive, probably active, or active by at least one reader, were age sex matched with an equal number of X-ray normals, to form the experimental and control groups respectively. Thus, a total of 2,106 were eligible for social investigation. Interview sheets, with particulars of the name and location of village, household number, and individual number and the identifiable data of the interviewees were made available to the social investigators at random for contacting and interviewing them at their homes. The interviews were non- suggestive in nature and deep probing on the details of symptoms experienced by the respondent, which were fully recorded. About 79% of the experimental group and 83% of the control group were satisfactorily interviewed, which constituted the data further analysed. Of the numerous symptoms recorded, only that were associated with pulmonary tuberculosis were considered, of which cough occurring for one month or more, fever for a month or more, pain in the chest, haemoptysis and all combination of these four symptoms were analysed statistically.

Cough was found to be the most important single symptom. It was not only the most frequent symptom alone or in combination in the experimental group but was less frequent in the control group that 69% of sputum positive and 46% of radiological positive had cough while only 9% of the control group had it. Considerably fewer people had fever and pain in the chest. Pain in the chest appears to be non- specific, giving a ratio of only 2:l among the experimental and control groups while fever was in the ratio of 6:l and haemoptysis was ll:l. It was seen that 69% of the sputum positive cases, 52% of the X-ray active or probably active, 29% of the inactive and 15% of the normals (control group) had at least one of the above mentioned symptoms. In all the groups, the proportion of symptoms were higher among males than among females. In both males and females the prevalence of symptoms was higher in the middle age groups than among the younger or older groups. This age variation was more marked in the females. The findings of the study were analysed further along with the data obtained from a couple of minor investigations, conducted in the rest of the 28 villages which formed the total of the villages surveyed epidemiologically. This brought out further that 95% of bacteriologically positive cases are aware of symptoms, 72% experience 'worry awareness' and 52% form the action taking group. The above findings have been of considerable importance in planning further studies and in formulating the National Tuberculosis Programme.

KEY WORDS: SOCIAL AWARENESS, SYMPTOMS, SOCIAL ASPECTS, CASE, SUSPECT CASE.
 

 
  ASSESSMENT & EVALUATION  
 
 
170
DIAGNOSIS OF SPUTUM POSITIVE TUBERCULOSIS CASES PREVALENT IN A DISTRICT OF SOUTH INDIA
R Channabasavaiah & AK Chakraborty: J Com Dis 1979, 11, 101-11.

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.

KEY WORDS: PREVALENCE, CASE, CONTROL PROGRAMME, RURAL POPULATION, CASE DETECTION, IMPACT.
 
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