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A COMPARISON BETWEEN LONGITUDINAL AND TRANSVERSE
DIAMETERS OF TUBERCULIN TEST INDURATIONS |
Kul Bhushan, MN Mukherjee, SP Chattopadhya & KT
Ganapathy: Indian J Med Res 1972, 60, 1724-30. |
In the epidemiological surveys carried out by the
National Tuberculosis Institute (NTI), Bangalore, instead of reading
the tuberculin reactions (indurations) by measuring their transverse
diameters as is done conventionally, the longitudinal diameters
were read. Later on, as the longitudinal diameters were observed
to be larger than the transverse diameters, an investigation was
carried out to study whether this difference would affect the estimation
of infection rates. Out of 1,240 tuberculin tested persons, for
1,189 both transverse and longitudinal diameters were read by each
of two readers, one accustomed to read the longitudinal diameter
and the other, the transverse diameter. All care was taken to avoid
bias on the part of the readers. All four reading were available
for 1,075 persons (87%).
It was found that longitudinal diameters were larger
than the transverse diameters for all ranges (of sizes) of reactions
when either diameter for each reader was taken as standard. The
prevalence of infection, considering 10mm+ reactions as the minimum
level for those infected, were almost the same for both the diameters
and for both the readers. Analysis according to age sex gave similar
results. Variations between the readers are known to be of much
higher magnitude than those observed between the diameters in this
study. The levels of post-vaccination allergy calculated on the
basis of longitudinal diameters, however, will be larger than those
for transverse diameters. In view of the above results, the findings
of the NTI epidemiological surveys wherein longitudinal diameters
of tuberculin reaction are read, will not only be comparable with
other studies conducted by NTI but also with studies done by other
organizations-national or international.
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KEY WORDS: TUBERCULIN, INDURATION SIZE, TRANSVERSE
DIAMETER, LONGITUDINAL DIAMETER. |