|EFFECT ON TUBERCULIN ALLERGY OF TUBERCULIN TESTS
GIVEN 18 MONTHS EARLIER
|Raj Narain, GD Gothi, KT Ganapathy & CV Shyama
Sunder: Indian J Med Res 1979, 69, 886-92.
Enhancing effect of tuberculin allergy as a result
of repeat tests with 1 TU RT 23 on groups tested with I TU, 20 TU
and placebo was studied by random allocation among population not
vaccinated with BCG in 8 villages. In all, 2357 persons were tested
with 1 TU and 759 with normal saline at first round. Based on testing
at three rounds the study population could be divided into eight
different groups and were labelled with alphabets 'a' to 'h' having
been tested once, twice or thrice. The groups 'a', 'c', 'e' &
g' were tested at 2 months, round two with 1 TU RT 23 and
remaining half were not tested. However, all available persons in
the 8 groups were retested at the third round, 18 months after the
initial test. Thus, eight groups cannot be treated as independent
samples but representative of the whole population.
The study did not show enhancing effect due to
previous tuberculin test with 1 TU alone among groups tested once,
twice or thrice after an interval of 18 months. Part of population
was tested with 20 TU at round one; boosting effect was seen at
2 months when test was repeated. However, it was not seen after
18 months but when exactly the boosting effect disappeared was not
known. Thus, there was no increase in reaction even among those
who were tested with a higher dose of 20 TU earlier after 18 months.
The groups provided the largest number for comparison between tested
and the control groups. It is inferred from the study that boosting
with high dose or repeat tests with the same dose does not persist
after 18 months. Hence, for classifying positive tuberculin reactors,
no correction is required to the same individuals/population after
an interval of 18 months or more, as no boosting effect after 18
months has been observed, on the basis of this analysis.
|KEY WORDS: TUBERCULIN TEST, TUBERCULIN ALLERGY,