Abstract
The present paper gives the results of a study on tuberculin reaction size—erythema and induration—at different intervals after intradermal testing with 1 TU.
In the course of tuberculin-testing some 18,000 textile workers in Mehalla el Kobra, Egypt, the tuberculin reactions of 417 men were read daily for five days after the tests had been given. The successive readings were made by the same observer without reference to his previous readings.
No difference of any practical significance was found between the results of readings made on the second through the fifth day. Almost all the reactions of over 6 mm of induration on any one day (except the first) remained above 6 mm on the subsequent days, and those measuring 0-6 mm did not exceed 6 mm on the later days. Thus, whether the reactions had been read on the second, third, fourth, or fifth day, essentially the same persons would have been classified as positive and negative according to the induration-reaction size.
Erythema could have served as well as induration for separating the study population into the same two groups, had 0-8 mm of erythema been defined as negative and erythema of 9 mm or more as positive for reactions read on the second through the fifth day.
In tuberculin surveys of the population under study there would thus have been no need to adhere to a fixed reading interval.
The material included in the present paper illustrates how the results of a relatively small and inexpensive preliminary study may serve to simplify and rationalize subsequent large-scale work.
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