Comparative thresholds for adenosine monophosphate (AMP) and methacholine (MCH) challenge testing

Abstract

Rationale Current use of the PC20 threshold for bronchial challenge precludes its use in more severe asthmatics with FEV1 <60%. We aim to evaluate whether the doubling dilution (dd) shift in PC10 and PC15 in response to anti-inflammatory treatment correlates with the shift in PC20. Methods We examined, retrospectively, data from previously published studies [n=8, 4 using AMP, 4 using MCH] and recalculated 10% and 15% thresholds for AMP and MCH.MCH data were pre and post inhaled corticosteroid (ICS) [n=3] and pre and post monteleukast (ML) [n=1]. AMP data were either: pre and post ICS [n=1], antihistamines [n=1] or ML [n=2]. Results 175 individual MCH challenges and 152 AMP challenges were evaluated. Pearson correlation coefficients and P values are shown. MCH PD20 vs. PD15: 0.80 (1.5×10 −40). MCH PD20 vs. PD10: 0.65 (2.0×10 −22). AMP PC20 vs. PC15: 0.96 (7.2×10 −85). AMP PC20 vs. PC10: 0.84 (7.8×10 −43). Subgroup analysis of AMP for pre and post ICS only [n=22] shows: AMP PC20 vs. PC15: 0.917 (1.9×10 −17). AMPPC20 vs. PC10: 0.843 (2.2×10 −12). Conclusions Our data suggest that lower 10% or 15% thresholds may be used for both challenges, although the relationship to the 20% threshold was strongest for AMP.