|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.
|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.