|TUBERCULIN SENSITIVITY IN YOUNG CHILDREN (0-4 YEARS
OLD) AS AN INDEX OF TUBERCULOSIS IN THE COMMUNITY.
|NL Bordia, Anton Geser, J Maclary, I Mundt & Kul
Bhushan: Indian J TB 1960, 8, 25-43.
The purpose of this study was to find out whether
the prevalence of infection in young children might be used as an
index of the tuberculosis problem in a population. Tuberculin testing
was done in a random sample of 2,883 children (0-4 years) in Bangalore
city, of those 2,589 (89.8%) actually completed testing. A total
of 4340 children were registered in 59 villages and of these 4090
(94.2%) were tuberculin tested. The villages were from Bangalore,
Kolar and Mandya as these districts were within 100 miles from Bangalore
city. The team went from house to house and made a complete registration
of the children 0-4 years in the selected houses. Information on
socio-economic status, density of population etc., was also collected
before giving tuberculin 1 TU RT 23 with Tween 80.
The results of the study showed that prevalence
of infection in 0-4 years age group of cantonment area was 1.6%
and in the crowded city area 4.1% at 14mm induration level. In the
rural population, the prevalence of tuberculosis infection was 2%.
In the city, a positive correlation between tuberculosis infection
and socio-economic condition was obtained while it was not seen
in rural areas. It was not possible to establish any correlation
between tuberculosis disease and infection either in rural or urban
areas, as the population was not examined for the prevalence of
|KEY WORDS: PREVALENCE, INFECTION, CHILDREN,
RURAL, URBAN, COMMUNITY.
|RESURVEY OF 15 VILLAGES FROM THE MADANPALLE ZONE
OF NATIONAL SAMPLE SURVEY ON TUBERCULOSIS
|Raj Narain, MV Jambunathan & M Subramanian: Proceed
Natl TB & Chest Diseases Workers Conf, Bangalore, 1962,
A study was undertaken with the following objectives:
(1) To estimate the proportion of population that would be available
for resurvey after 5 years. (2) To ascertain five years later the
fate of persons with X-ray pathology. (3) To compare the prevalence
of tuberculosis in the villages at an interval of 5 years. Population
of 15 of the 31 villages from the Madanapalle zone, was selected
for this study. About 9,500 persons were registered and 7,200 were
X-rayed at the initial survey. Five years later the same population
was re-examined and nearly 70% were available for X-ray examination.
Sputa were collected from persons with abnormal X-ray shadows interpreted
as such by either of the two readers. Two spot samples were collected
within an interval of 1-3 days and were examined by direct smear
and by culture.
Analysis of the data shadow showed that: (1) There
was no significant difference in the prevalence rates i.e., 3.6
and 4.6 per thousand respectively at two points of time. (2) During
the interval, 30% of active cases had died and 20% were still active
at the end of 5 years. (3) There was almost complete turn over of
the bacillary cases during the 5 years interval.
|KEY WORDS: RESURVEY, COVERAGE, PREVALENCE, MORBIDITY,
|SOME ASPECTS OF A TB PREVALENCE SURVEY IN A SOUTH
|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.
|A COMPARISON OF THE RELATIVE VALUE OF SINGLE AND
DOUBLE PICTURE TECHNIQUES IN TB PREVALANCE SURVEYS
|Raj Narain, SS Nair & P Chandrasekhar: Indian
J TB 1964, 11, 145-53.
Limitations of a single X-ray picture for locating
and interpreting shadows in the chest had been studied earlier.
In order to reduce these limitations, it was suggested that two
pictures of each person be taken where the second picture was to
be taken after a vertical displacement of X-ray tube, up or down
by about 4 to 5cms. The advantages of taking two pictures simultaneously
as compared to a single picture have not been studied so far. Two
mobile X-ray units each with an odelca camera were alternated for
the single and double picture examinations. A total of about 2,000
persons were X-rayed and were read independently by 3 readers. A
spot sample of sputum was collected 3-4 days later from persons
with abnormal X-ray shadows and was examined by direct smear microscopy.
Comparison of the readings of the two sets of pictures
did not show a better agreement between different (inter-
individual) readers or between two different readings of the same
reader (intra-individual) when the two picture technique was used.
The X-ray cases detected by double picture only by any one reader
were not confirmed, more often than those detected by single picture
only. The X-ray pictures of the bacillary cases were also not interpreted
more often as active tuberculosis by the two picture technique.
It was concluded that the double picture technique does not offer
any advantage over the single picture technique.
|KEY WORDS: SURVEY, PREVALENCE, X-RAY READING,
X-RAY FILM, SINGLE PICTURE, DOUBLE PICTURE.
|DISTRIBUTION OF INFECTION AND DISEASE AMONG HOUSEHOLDS
IN A RURAL COMMUNITY
|Raj Narain, SS Nair, G Ramanatha Rao & P Chandrasekhar:
Bull WHO 1966, 34, 639-54 & Indian J TB 1966, 13, 129-46.
Studies on the distribution of tuberculous infection
and disease in households have mostly been restricted to the examination
of contacts of known cases. Clinical experience has lead to a strong
belief that tuberculosis is a family disease and contact examination
is a must for case-finding programmes. A representative
picture of the distribution of infection and disease in households
can be obtained only from a tuberculosis prevalence survey.
This paper reports an investigation, based on a
prevalence survey in a rural community in south India. The survey
techniques and study population have been described in an earlier
report. Briefly, the defacto population was given a tuberculin test
with 1 TU of PPD RT 23 with Tween 80 and those aged 10 years and
above were examined by 70mm photofluorography. All the X-ray pictures
were read by two independent readers. Those with any abnormal shadows
by either of the two readers were eligible for examination of a
single spot specimen of sputum by direct smear and culture. The
defacto population numbered 29,813 and tuberculin test results were
available for 27,115. After excluding BCG scars, the study population
of 24,474 was distributed over 5,266 households which were further
classified as bacillary case household with atleast
one bacteriologically confirmed case, X-ray case household
with atleast one radiologically active case but with no bacillary
cases and non-case household with neither a bacillary
nor an X-ray case. Total bacillary cases were 77 and were distributed
in 75 household. 74 households had one case each and one household
had 3 bacillary cases.
The findings of the study have thrown considerable
doubt on the usefulness of contact examination in tuberculosis control;
(1) over 80% of the total number of infected persons, in any age
group, occurred in households without cases, (2) cases of tuberculosis
occurred mostly singly in households, and the chance of finding
an additional case by contact examination in the same household
is extremely small, (3) a common belief has been that prevalence
of infection in children in 0-4 age group is a good index of disease
in households, but in this study about 32% of households with cases
of tuberculosis had no children in this age group, (4) in houses
with bacteriologically confirmed case only 12% of the children in
0-4 age group showed evidence of infection, a possible explanation
of such a low intensity of infection could be that there is resistance
to infection. It is well known that some children even after repeated
BCG vaccination do not become tuberculin positive. It is felt that
a large number of children do inhale tubercle bacilli, but a primary
complex does not develop or even if it develops, the children remain
tuberculin negative. A hypothesis has been made that in addition
to resistance to infection, there is something known as resistance
to disease. Otherwise, it is difficult to explain why under
conditions of heavy exposure in infection, only some individuals
develop evidence of infection and very few develop disease thereafter.
|KEY WORDS: PREVALENCE, INFECTION, DISEASE,
CONTACT EXAMINATION, HOUSEHOLD, RURAL COMMUNITY.
|FATE OF CASES DIAGNOSED IN A SURVEY
|Raj Narain, G Ramanatha Rao, G Chandrasekhar &
Pyare Lal: Proceed Natl TB & Chest Dis Workers Conf,
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
|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,
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
|KEY WORDS: M.TUBERCULOSIS, SENSITIVE STRAINS,
RESISTANT STRAINS, CASE, FATE, PREVALENCE, INFECTIVITY.
|SOME EPIDEMIOLOGICAL ASPECTS OF TUBERCULOUS DISEASE
AND INFECTION IN PAEDIATRIC AGE GROUP IN A RURAL COMMUNITY
|GD Gothi, SS Nair & Pyare Lal: Indian Paediatrics
1971, 8, 186-94.
The prevalence and incidence rates of tuberculous
infection and disease in the community are known in the age group
10 years and above from several surveys carried out so far. The
present paper provides various parameters of tuberculosis in particular
in the pediatric age group. A random sample of 119 villages in 3
taluks of Bangalore district were surveyed 4 times from May 1961
to July 1968 at intervals of 18 months, 3 years and 5 years of the
initial survey. Tuberculin test was done for the entire available
population with 1 TU PPD RT 23 with Tween 80, and 70mm X-ray for
all available persons aged 5 years and above. Two samples of sputum
were obtained from the X-ray abnormals, and examined by smear and
It was found that prevalence of infection increased
with age from 2.1% at 0-4 year age group to 16.5% at 10-14 year
age group, compared to 47% at 15 years and above age group. Prevalence
of disease in 5-14 year age group was considerably lower than in
age group 15 years or more. Tuberculosis morbidity increased with
the size of tuberculin reaction and it was high among children with
reaction 20mm or more. Incidence of infection increased with age
from 0.9% per year in age group 0-4 years to 2.8% per year among
that of 15 years and above. Incidence of disease also showed the
same phenomenon-, rising from 0.5% in age group 5-9 to 4% per year
in the age group 15 years and above. There were 10 sputum positive
cases in 5-14 years of age in first survey, of them, 8 became negative
and one died. While from among 152 cases in 15 years and above age
group, 48 became negative, 72 died and 32 remained positive. The
fate of cases of pulmonary tuberculosis in 5-14 years age was not
as serious as in 15 years and above age group. The survey had no
means of examining miliary and meningeal tuberculosis.
Children as well as adults with larger reaction
of 20mm or more to tuberculin test had higher mortality. This could
be considered due to tuberculous infection after taking into account
death due to non- tuberculous reasons in both the infected and uninfected
groups. Use of chemoprophylaxis might be considered for those who
give history of contact with open cases and have tuberculin reaction
size 20mm or more.
|KEYWORDS: CHILDREN, RURAL COMMUNITY, PREVALANCE,
INCIDENCE, INFECTION, DISEASE, TUBERCULIN, INDURATION SIZE, MORTALITY,
|PROBLEMS IN DEFINING A CASE OF PULMONARY
TUBERCULOSIS IN PREVALENCE SURVEYS
|Raj Narain, SS Nair, K Naganna, P Chandrasekhar, G
Ramanatha Rao & Pyare Lal: Bull WHO 1968, 39, 701-29.
Generally there is no acceptable definition of
the term case of pulmonary tuberculosis, although such
a definition is of fundamental importance both in clinical medicine
where results of various chemotherapeutic regimens are compared,
as well as for the comparison of different epidemiological data.
The main purpose of this paper is to focus attention on the difficulties
of defining a case on the basis of bacteriological examination,
X-ray examination and tuberculin test. Data from two successive
prevalence surveys in a random sample of 134 villages in Bangalore
district with a population 70,000 have been utilized to illustrate
some of the difficulties in defining a case of pulmonary
tuberculosis for reporting the prevalence or incidence of the diseases.
The entire population was tuberculin tested with 1 TU RT 23 with
Tween 80 at both rounds and those 5 years of age and older were
examined by 70mm photofluorogram. The sputum specimens (spot and
overnight) were collected from those with any abnormality on X-ray
as recorded by either of the two independent readers. Both the specimens
were examined by fluorescent microscopy and Ziehl-Neelsen technique
and by culture.
Analysis of data has shown that the term a
case of pulmonary tuberculosis does not represent a single
uniform entity, but embraces cases of several types, differing considerably
in their tuberculin sensitivity, results of X-ray and sputum examination,
in the reliability of their diagnosis and mortality experience.
The status of cases found at initial and subsequent surveys showed
changes with time, and such changes show considerable differences
for the various types of cases. It was felt that a single straight-forward
definition of a case was not possible to suit all situations. One
has to use more than one definition. Although theoretically, finding
a single bacillus in sputum should be adequate proof of pulmonary
tuberculosis, it was shown that finding of a few bacilli (3 or less)
was very often due to artifacts and should not be the basis for
a diagnosis. It has also been found that positive radiological findings,
in the absence of bacteriological confirmation, indicate only a
high risk of the disease and not necessarily pulmonary tuberculosis.
Direct microscopy appears to be a consistent index of disease but
in community surveys has the limitation of missing a substantial
proportion of cases and of adding some false ones.
In view of the difficulty of providing a single
definition of a case of tuberculosis, four indices have been suggested.
(1) Cases definitely positive by direct smear; (2) Cases definitely
positive by culture; (3) All cases positive by culture (including
less than twenty colonies); (4) Sputum positive cases which are
radiologically active. Each of these could be used for different
situations. However, it was concluded that, there seems to be no
option but to use more than one definition for assessing the prevalence
and incidence of disease.
|KEY WORDS: CASE-DEFINITION, SURVEY, PREVALENCE,
|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.
|TUBERCULOSIS IN A RURAL POPULATION OF SOUTH INDIA:
A FIVE YEAR EPIDEMIOLOGICAL STUDY
|National Tuberculosis Institute, Bangalore: Bull
WHO 1974, 51, 473-88.
A rural population of 65,000 belonging to 119 randomly
selected villages of Bangalore district was repeatedly examined
four times during 1961 to 1968, by tuberculin test, X-ray and sputum
examinations, to study the epidemiology of tuberculosis without
any active anti-tuberculosis measures. The interval between the
first and the fourth examination was 5 years. The coverage of various
examinations at different surveys were very high.
The main findings of the study are: Prevalence
rate of tuberculous infection in the population was about
30% (among females 25% and males 35%). The overall prevalence
rates of infection were fairly constant at all the four surveys,
but a steady decrease in the prevalence of infection was observed
in the age group 0-24 years. Annual incidence rate of infection
on the average was about 1%. During the study period,
the incidence of infection showed a decline from 1.63% to 0.8% for
all ages combined. Prevalence rate of disease ranged from
337 to 406 per 1,00,000 population during the study period,
the highest being at the time of first survey and lowest at the
time of third survey. For the younger age group of 5-34 years, the
rates showed continuous decrease during the study period. Annual
incidence rate of disease ranged from 79 to 132 per 1,00,000
population, highest being between first and second surveys and lowest
between second and third surveys. The incidence rate in younger
age groups below 35 years showed a decline during the study period.
Those with tuberculin test induration of 20mm or more had highest
annual incidence rate of disease. The annual incidence rate
of bacteriologically confirmed disease in the three radiological
groups of population was (i) 185 per 1,00,000 with normal X-rays,
(ii) 958 per 1,00,000 with abnormal shadows judged as inactive
tuberculous are non-tuberculous and (iii) 4,530 per 1,00,000 with
abnormal shadows judged as active or probably active tuberculous
but bacteriologically not confirmed. The third group constituted
1% of the total population and contributed 34% of the total incidence
cases. In each of the above three radiological groups, the incidence
of disease was highest among those with tuberculin test induration
of 20mm or more to 1 TU RT 23 with Tween 80. Those with 20mm or
more tuberculin test induration in the third radiological group
constituted 0.45% of the total population but contributed 27% of
the total incidence cases. Incidence rate for males was nearly double
that of females. More than half of the new male cases were 35 years
of age, whereas more than half the females were below the age of
35 years. Out of 126 cases followed up at three subsequent surveys
over a period of 5 years, 49.2% died, 32.5% got cured and 18.3%
continued to remain sputum positive. Both death and cure rates
were highest during the first one and a half year period.
About 30% of newly detected cases come from population
uninfected at an earlier survey. Both infection and disease showed
a decline in the younger age group. There was no evidence of an
increase in drug resistance among newly diagnosed cases. Incidence
of cases showed a higher natural cure. These findings indicate that
tuberculosis cases are not a uniform entity. There can be different
gradations from the point of view of diagnosis and ability to benefit
from treatment. The differences between male and female patients
with regard to death and cure rates support this view
|.KEY WORDS: TREND, RURAL POPULATION, PREVALENCE,
INCIDENCE, INFECTION, DISEASE, LONGITUDINAL SURVEY.
|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.
|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.
|PREVALENCE OF NON-SPECIFIC SENSITIVITY TO TUBERCULIN
IN A SOUTH INDIAN RURAL POPULATION
|AK Chakraborty, KT Ganapathy, SS Nair & Kul Bhushan:
Indian J Med Res 1976, 64, 639-51.
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.
|KEY WORDS: NTM, PREVALENCE, INFECTION, BOOSTING,
TUBERCULIN REACTION, RURAL POPULATION.
|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.
|TUBERCULOSIS IN CHILDREN IN A SLUM COMMUNITY
|GD Gothi, Benjamin Isaac, AK Chakraborty, R Rajalakshmi
& Sukant Singh: Indian J TB 1977, 24, 68-74.
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.
|KEY WORDS: CHILDREN, SLUM COMMUNITY, PREVALENCE,
INFECTION, PEDIATRIC TUBERCULOSIS.
|USE OF 20 TU RT 23 AND 5 TU BATTEY ANTIGEN FOR ESTIMATION
OF PREVALENCE OF NON-SPECIFIC TUBERCULIN SENSITIVITY
|GD Gothi, AK Chakraborty, MJ Jayalakshmi & KT Ganapathy:
Indian J Med Res 1977, 66, 389-97.
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.
|KEY WORDS: BATTEY ANTIGEN, PREVALENCE, NON SPECIFIC
|PREVALENCE AND INCIDENCE OF SPUTUM NEGATIVE ACTIVE
PULMONARY TUBERCULOSIS AND FATE OF PULMONARY RADIOLOGICAL ABNORMALITIES
FOUND IN A RURAL POPULATION
|GD Gothi, AK Chakraborty, VV Krishnamurthy & GC
Banerjee: Indian J TB 1978, 25, 122-31.
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%.
|KEY WORDS: SUSPECT CASE, PREVALENCE, INCIDENCE,
RURAL POPULATION, FATE.
|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,
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
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.
|PREVALENCE OF INFECTION AMONG UNVACCINATED CHILDREN
FOR TUBERCULOSIS SURVEILLANCE
|AK Chakraborty, KT Ganapathy & GD Gothi: Indian
J TB 1980, 72, 7-12.
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
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
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.
|KEY WORDS: PREVALENCE, INFECTION, BCG SCAR,
|PREVALENCE, INCIDENCE AND FATE OF SUSPECT CASES
OF TUBERCULOSIS IN A RURAL POPULATION OF SOUTH INDIA
|VV Krishna Murthy: NTI Newsletter 1982, 19, 75-80.
The data from a longitudinal survey conducted in
Bangalore district from 1961-1968 by National Tuberculosis Institute
was analysed to find out the prevalence, incidence and fate
of suspect cases. In brief, the survey was conducted in 119
randomly selected villages in three taluks of Bangalore district
and repeated within the next five years. At each survey, eligible
population was subjected to tuberculin, X-ray & sputum smear
and culture examinations.
The overall prevalence rate of suspect cases among
persons aged five years and more was 1.06% at I survey, 0.68%, 0.49%
and 0.43% at II, III and IV survey respectively. In males, the prevalence
rate was 1.19% at I survey & 0.62% at IV survey corresponding
figures for females were 0.94% and 0.24% respectively. A decline
of prevalence of suspect cases from 1.06% at I survey to 0.43% at
IV survey was observed. The overall incidence of suspect cases was
0.16% between I & II surveys, 0.10% between II & III, and
0.06% between III & IV surveys. The overall as well as age specific
annual incidence rates between III & IV surveys were significantly
less than that between I & II surveys. At all the three intervals
the incidence increased with the age. Incidence of suspect cases
in males was more than that in females. Change in disease status
over a period of time is termed as "fate". The
disease status was classified as (i) cure (ii) continued to be suspect
case (iii) converted into bacillary cases and (iv) dead. The percentage
of cure (51.9%, 53.2% and 50.3%) and conversion into bacillary cases(7.2%,5.8%
and 5.4%) were almost the same at all the three intervals. But the
percentage of those who remained suspect cases reduced from 33.5%
at the end of 18 months to 17.5% at the end of 60 months. On the
other hand, the death rate increased from 7.4% at the end of 18
months to 26.8% at the end of 60 months. The decreasing trend of
continuing to be suspect cases at the rate of 10% between two observations,
appears to be corresponding to the increasing trend in the death
rate as seen from the observations made at the three intervals.
|KEY WORDS: PREVALENCE, INCIDENCE, FATE, SUSPECT
CASE, RURAL COMMUNITY, LONGITUDINAL SURVEY.
|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.
| CHANGES IN THE PREVALENCE RATES OF INFECTION IN
YOUNGER AGE GROUPS IN A RURAL POPULATION OF BANGALORE DISTRICT OVER
A PERIOD OF 5 YEARS
|AG Kurthkoti & Hardan Singh: NTI Newsletter
1985, 21, 28-40.
The utility of repeated estimates of prevalence
rates of infection in children as a tool for surveillance in tuberculosis
is now well recognized. Two prevalence surveys at an interval of
5 years were conducted by National Tuberculosis Institute, Bangalore,
with the main objective of studying changes in prevalence rate of
infection among children in the age group of 0-9 years. A total
population of 42,343 residing in 90 randomly selected villages of
Doddaballapur taluk, Bangalore, were registered; of them, 12,535
were children in the age group of 0-9 years. Children were further
classified into two sub groups 0-4 and 5-9 years, with or without
BCG scars. The unvaccinated children in these two age groups formed
the study population.
The population in the study area during the 2nd
repeat survey was similar to that of first survey with regard to
age, sex distribution, except that a growth rate of 1.1% per year
was registered. The BCG scar rate, among children in the age group
0-4, 5-9 years, was 8% & 39% respectively at survey I. All the
unvaccinated children below 10 years were given tuberculin test
with 1 TU PPD RT 23 and reactions were read 72 to 96 hours after
tuberculin testing. In the first survey, level of demarcation to
classify the infected children was 10 mm and above, while in II
survey it was 12 mm and above. It was observed that the prevalence
rate of infection from I survey to II survey was not altered (2.58%
& 2.46%) in the 0-4 years of age, while there was an increase
in the rate from 8.93% to 12.3% in 5-9 years of age in the II survey.
The increase in the infection rate could be attributed to the rising
trend of infection, over reading by tuberculin-readers', skills
of both tuberculin tester and reader, boosting of tuberculin reaction
or scarless BCG vaccination. In conclusion, the study of changes
in the prevalence rate of infection in the younger age group is
simple, cheap, less time consuming. The data can be used for calculating
annual risk of infection as well trend of transmission of infection.
|KEY WORDS: TREND, RISK OF INFECTION, PREVALENCE,
SURVEILLANCE, RURAL COMMUNITY.
| 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.