| 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.