|INTERPRETATION OF PHOTOFLUOROGRAMS OF ACTIVE PULMONARY
TB PATIENTS FOUND IN EPIDEMIOLOGICAL SURVEY AND THEIR FIVE YEAR FATE
|GD Gothi, AK Chakraborty & GC Banerjee: Indian
J TB 1974, 21, 90-97.
In this study the material from Five year
study of Epidemiology of Tuberculosis (1961-68) has been analysed
to find out an improved method of interpretation of chest X-rays
to get accurate estimation of prevalence of suspects
in the community. The population of a random sample of 119 villages
from the three taluks of Bangalore district was surveyed four times
with intervals of 1½ to 2 years by tuberculin testing, 70mm
chest photofluorography and sputum bacteriology. Out of 45,434 persons
X-rayed during the first survey, 590 were read as active pulmonary
tuberculosis on the basis of single picture interpretation by two
independent readers. Of them, 460 being sputum culture negative
were classified as initial suspects and these were reviewed
in this study by the panel of three readers together by the method
of joint reading. The interpretation was done comparing
the serial X-rays of individuals taken at intervals along with other
available examination results and personal data. Out of 460 initial
suspects only 110 (23.9%) were confirmed as suspects,
the remaining were judged as non-tuberculous and/or inactive tuberculous
(62.2%) and normals (13.9%).
Fates on five year follow up were compared between
85 confirmed suspects and 385 initial suspects.
The mortality and sputum positive status were found more among the
former group i.e., 23.5 and 25.5 and 14% and 7.2% respectively.
Radiologically, 48.7% of the confirmed suspects and only 10% of
the initial suspects could be classified as suspects at 5th year
follow up. Incidence of bacillary disease among the confirmed suspects
was also found higher. On the basis of joint reading
and five year follow up study, the limitations of single picture
interpretation resulting in considerable over diagnosis were clearly
seen. The comparative reading of serial X-rays along with other
examination results did help in the better assessment of etiology
and activity status of disease. Of the X-rays read as non-tuberculous
and inactive tuberculous when reviewed by joint reading
method, about 67 more suspects could be added. Even then the estimates
of prevalence of suspects based on single film interpretation
which are widely used in India appear to be about 3 times the actual
|KEY WORDS: FATE, SUSPECT CASE, X-RAY, JOINT
READING, SINGLE PICTURE, OVER DIAGNOSIS.
|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.