Comparative cutoff points for adenosine monophosphate and methacholine challenge testing

Current use of the PC 20 (provocation concentration that causes a decrease in forced expiratory volume in 1 second of 20%) cutoff point for bronchial challenge precludes its use in patients with more severe airflow obstruction. To evaluate the efficacy and safety of lower cutoff points for adenosine monophosphate (AMP) and methacholine (MCH) bronchial challenge tools to monitor response to treatment in chronic asthma. We retrospectively examined data from 5 previously published studies (2 using AMP, 2 using MCH, and 1 with MCH and AMP arms) and recalculated 10% and 15% cutoff points for AMP and MCH. Data were analyzed for correlation of single results and doubling dose shifts after anti-inflammatory treatment intervention. A total of 175 individual MCH challenges and 152 AMP challenges were evaluated. Evaluating the doubling dose shift produced by the addition of anti-inflammatory treatment (inhaled corticosteroids or montelukast) produced the following Pearson correlation coefficients: MCH PD 20 (provocation dose that causes a decrease in forced expiratory volume in 1 second of 20%) vs PD 15, 0.80; MCH PD 20 vs PD 10, 0.65; AMP PC 20 vs PC 15, 0.96; and AMP PC 20 vs PC 10, 0.84 ( P < .001 for all). Subgroup analysis of AMP for before and after inhaled corticosteroids only (n = 41) shows AMP PC 20 vs PC 15 of 0.92 and AMP PC 20 vs PC 10 of 0.84 ( P < .001 for both). The 10% and 15% cutoff points strongly predict the 20% cutoff value for AMP and MCH, as do the doubling dose shifts after anti-inflammatory treatment. The lower thresholds are suitable for monitoring response to therapy, and they expose patients to significantly less provocation agent.