Comparison of different agents for bronchial challenge tests

Methacholine bromide(MBr) was commonly used for bronchial challenge testing(BCT). Since Dec '23, MBr was not available anymore, resulting in a switch to histamine diphosphate(HDP). In Feb '24 we were able to switch to methacholine chloride(MCl). According to the literature similar outcomes have been demonstrated with MCl and HDP. <bold>Aim:</bold> The aim of the study was to investigate whether there is a difference in the percentage of positive BCTs when using MBr, HDP or MCl with a modern breath-actuated nebulizer(BAN). <bold>Methods:</bold> Percentages of positive BCTs in adults were compared between MBr, HDP and MCl, executed between Dec ’22-Jan ’23 and Dec ’23-Feb ’24, using the Fisher’s exact test. All tests were performed with a 1-minute tidal breathing protocol. Tests were considered positive if there was a Provocative Dose causing a 20% fall in FEV1(PD20). A quadrupling protocol was used for MBr and MCl. For HDP, because of the side effects, a doubling protocol was used. <bold>Results:</bold> The groups were similar in age and BMI, 64% were females. The percentage of positive tests was significantly higher for HDP compared to MBr and MCl (p<0.001). There was no significant difference between MBr and MCl (p=0.275). <fig><object-id>erj;64/suppl_68/PA2325/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> <bold>Conclusion:</bold> The percentage of positive BCTs is significantly higher when using HDP instead of MBr or MCl. The reason for the difference between MBr, MCL and HDP needs to be investigated. Artificial intelligence could have a role in identifying unexpected patterns like these sooner.