|THE USE OF SCREENING TOOLS FOR THE ESTIMATION OF
TUBERCULOSIS CASE RATES IN A COMMUNITY
|AK Chakraborty: Indian J Public Health 1980, 24,
The problem in using simple tools e.g. chest symptoms
for epidemiological surveys, designed to quantify the problem is
that estimates from these simple surveys are considerable underestimates.
Recent research has, however, paved the way for the use of these
simpler tools for use in estimating tuberculosis case prevalence
rates in the community. A tool which is simple, convenient to use
and maintain, cheap but highly sensitive is called "screening
tool". Such tools are used for making initial selection of
the given population. Tuberculin test, X-ray & symptom elicitation
are the main screening tools used for epidemiological surveys and
TB Control Programme. In the programme, symptom elicitation and
X-ray examination are the screening tools of choice for Case-finding.
In the survey, tuberculin and X-ray are the only two tools used,
although tuberculin is not a good screening tool (40% population
infected). Use of symptom screening in surveys, however, is restricted
in the absence of adequate information on comparison of prevalence
rates obtained by this method of screening with the best estimate.
The performance of symptom screening with either culture or smear
microscopy have been attempted. They showed that by applying suitable
correction factors they may be rendered comparable to the best estimate.
The symptoms may be useful in the survey as a screening tool and
may give the rates as proximate to the true rates as possible. They
will enable considerable simplification of epidemiological studies
in tuberculosis without compromising on the precision of the estimates
|KEY WORDS: SCREENING TOOLS, ESTIMATES, CASE
RATE, SYMPTOMS, X-RAY, TUBERCULIN, SURVEY.
| 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.