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Published on: August 11, 2018
Comparison of different methods and times for reading the tuberculin skin test
O Morán-Mendoza1, M C Tello-Zavala, M Rivera-Camarillo
1Division of Respirology and Critical Care Medicine, Queen's University, Kingston, Ontario, Canada.
Background:
Current guidelines vary on the recommended method and time for measuring tuberculin skin test (TST) indurations.
Objective:
To evaluate the best time and method for assessing TST results and which purified protein derivative (PPD) to administer.
Design:
Standard PPD (PPD-S) and PPD-RT23 were applied concurrently on each forearm in random order in 78 nurses.
Measurements:
TST induration was measured at 48, 72 and 96 h by two nurses by palpation and a ruler, palpation and a Vernier caliper, ballpoint pen and a ruler or ballpoint pen and a Vernier caliper. TST differences were assessed using mixed-effects analysis. We also assessed the rate of false-positive/-negative results and the variability of the TST measurements.
Results:
We performed 767 TST measurements. The adjusted mean TST size was larger with PPD-S than with PPD-RT23 (12.8 vs. 10.8 mm, P < 0.001), and at 72 h than at 48 h and 96 h (13.4 vs. 11.8 vs. 10.1 mm, P < 0.05). The smallest number of false results was observed with PPD-S, the ballpoint pen-ruler and at 72 h; palpation+ruler had the least variability at 72 h.
Conclusions:
The TST should ideally be performed with PPD-S and measured at 72 h with the ballpoint pen+ruler or palpation+ruler methods.
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