Comparative Study Between Bronchial Challenges With Methacholine And Adenosine In Asthma Diagnosis

RATIONALE: Bronchial hyperresponsiveness is usually measured by bronchial challenge with direct (e.g. methacholine) and indirect (e.g. adenosine) agonists. A prospective, randomized, crossover, single-blind study was performed to compare both methods in the diagnosis of asthma. METHODS: Fifty-seven patients were selected (21 male, 36 female). Fifty-four underwent both challenges following the five-breath dosimeter protocol. PC20 was calculated according to ATS guidelines. Data of symptoms developed during the challenge, PC20 methacholine and adenosine, and FEV1 improvement after bronchodilator therapy were recorded. RESULTS: Symptoms at consultation were consistent with asthma in 68.4% patients, asthma and rhinitis in 29.8% and exercise-induced asthma in 1.8%. Atopy was reported in 93%; 49.1% had family history of atopy and 26.3% of asthma. The most frequent symptoms developed during the challenge were cough (40.4% with adenosine and 20.4% with methacholine) and wheezing (26.3% and 7.4% respectively), statistically significant differences. In 30 patients challenge with adenosine was positive (52.6%). Twenty-seven of them underwent methacholine, being positive in 24. Every patient with negative result to adenosine, was also negative to methacholine. Positivity of both challenges was only associated with having a positive skin prick test to danders (p = 0.001). In 94.4% subjects the result of both challenges was concordant (kappa index = 0.889). PC20 in both challenges showed poor linear correlation (Pearson r = 0.43, p < 0.05). Percentage of improvement after bronchodilator was 34.9% (SD12.2%) with adenosine challenge and 33.9% (SD17.9%) with methacholine (not significant). CONCLUSIONS: Concordance in the result of both techniques is very high. Cough and wheezing are more frequent with adenosine. PC20 shows poor linear correlation.