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018
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.

KEY WORDS: TUBERCULIN, INDURATION SIZE, TRANSVERSE DIAMETER, LONGITUDINAL DIAMETER.
 

 
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129
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.

The purpose of this investigation was to compare the corresponding longitudinal and transverse diameters of tuberculin test and study the influence of reader variations, size of reaction and the age specific infection rates, in order to understand the effect of switching over from the transverse to longitudinal readings. The study was carried out in villages in south India where no BCG or tuberculin testing had been undertaken. A total of 1240 persons were given tuberculin test with 1 TU RT 23 in both longitudinal and horizontal diameters. The indurations were read after 2-4 days by two readers independently. The study showed that though the longitudinal diameters were bigger than the corresponding transverse diameters, these differences did not influence infection rates calculated at 10 mm or more induration level. In National Tuberculosis Institute (NTI), Bangalore the practice of reading transverse diameter was altered to longitudinal diameter in the epidemiological surveys as it was comparatively easier to read the longitudinal diameter. Obtaining almost similar infection rates at the 10 mm or more level of induration in this study, irrespective of readers and diameters has minimized the effect of the changeover from transverse to longitudinal diameter reading in the epidemiological surveys at NTI. This would also not pose any problem in comparing the results of NTI studies with other research studies by any national or international organisation where transverse diameters have been measured.

KEY WORDS: TUBERCULIN TEST, LONGITUDINAL, TRANSVERSE, TUBERCULIN INDURATION SIZE.
 
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