|LIMITATIONS OF SINGLE PICTURE INTERPRETATION IN
|Raj Narain & M Subramanian: Proceed Natl TB
& Chest Dis Workers Conf, Bangalore, 1962, 64-106.
Survey with MMR remains as one of the most important
methods available for measuring the size and extent of tuberculosis,
specially in developing countries. Its value in case-finding programmes
is well recognised. Nevertheless, mass miniature radiography with
a single picture of the chest has a wide margin of error owing to
the intra & inter-individual differences in X-ray reading. A
study was undertaken to know the errors involved by repeating an
X-ray picture after an interval of 3 to 4 months and judging the
first picture in the light of a comparative reading of the two pictures.
It is postulated that two pictures taken at an interval, may afford
better judgement regarding the assessment of a case than a single
picture only. A prevalence survey was carried out in Tumkur district
in 1960-61, among 62 villages and 4 towns; 20 villages were selected
for this study. A total of 8,000 persons were registered, 5,300
of them were X-rayed and re-read by two readers. Photofluorograms
were repeated after three and a half months after the first picture.
At the time of repeat X-ray, a spot sample of sputum was collected
from persons with abnormal shadows.
Briefly the findings of the study were: (1) About
20% of bacillary cases were among those with inactive or non- tubercular
shadows on the basis of a single X-ray film. (2) Inter-individual
agreement for X-ray active cases was of the order of 50%. (3) Intra-individual
agreement for X-ray active cases was 52% for one reader and 69%
for the two readers. (4) Mass miniature radiography with a single
film, in spite of its inherent limitations, is the best available
method both for surveys as well as for case-finding programmes due
to its ability to find cases as well as potential cases in a short
time. (5) Even the agreement between two sputum samples collected
within an interval of 1-3 days was 42% for positive results.
|KEY WORDS: X-RAY READING, LIMITATIONS, SINGLE PICTURE,
MMR, RURAL COMMUNITY.