Comparing the adrenaline-Pirquet test with international PPD tuberculin tests

Abstract

Several tuberculins, strengths and setting methods are in everyday use. We wanted to compare the Norwegian reference adrenaline-Pirquet test with the internationally recommended Mantoux PPD test and Rhoditest. In responders of a random sample of young adults, with randomization of test subjects, we intra-individually compared the adrenaline-Pirquet (aP) test with Norwegian-produced synthetic medium tuberculin (SMT) with either the Mantoux test with PPD 2 tuberculin units (TU) (M2), the Mantoux-PPD 5 TU (M5) or the PPD 2 TU-Rhoditest (Rh). The criteria for a positive reaction were ≥ 4mm for the aP test, ≥10 mm for the M2 test, ≥ 6mm for the M5 test and ≥2mm for the Rh test. Strongly positive reactions were defined as aP test ≥10 mm and M2/M5 test ≥15 mm. One of the tuberculin tests was positive while the comparison test was negative in 14% of the M2 test group (n = 236), 15% in the M5 test group (n = 162) and 20% in the Rh test group (n = 187). The three PPD tests had positive reactions 3-10 times as often, with a simultaneous negative aP test, than vice versa. Strongly positive reactions occurred in 7% of the aP tests (≥ 10 mm), 32% of the M2 tests (≥ 15 mm) and in 41% of the M5 tests (≥15 mm). Receiver operating characteristic (ROC) curves gave the best agreement, with aP test ≥ 3 mm compared with the M2 and the Rh tests. Regression equations are presented for transformations of the Norwegian reference method of adrenaline-Pirquet results to internationally recommended PPD tests. The international recommendations, globalization in general and the skill of Norwegian public health nurses in performing intra-dermal BCG suggest a future shift to the PPD 2 TU Mantoux test in Norway. Due to the lack of sensitivity and specificity of all tuberculin tests they might be used in targeted tuberculin testing and not as a general screening procedure in a low-incidence tuberculosis area with BCG-vaccinated inhabitants. © 2001 Harcourt Publishers Ltd.