Methacholine challenge test as an adjunctive investigative tool in patients with asthma-like symptoms: the Sabah experience

INTRODUCTION: Patients with asthma-like symptoms pose a diagnostic dilemma when physical examination is normal. The usual practice in Malaysia would be to give empirical asthma treatment. Bronchial challenge test (BCT) is widely used in many countries to diagnose asthma objectively but it is not widely available in Malaysia.
OBJECTIVE: To describe our experience with BCT using methacholine at Queen Elizabeth Hospital as a supporting tool in the investigation of patients with asthma-like symptoms.
METHODOLOGY: Review of case notes of patients who underwent BCT from July 2008 till April 2009. BCT was performed via dosimeter technique. Results were classified as high hyper responsiveness if the provocative dose of methacholine required to achieve 20% fall in FEV1 (PD20) was less than or equal to 0.125 micromol, moderate hyper responsiveness if PD20 was between 0.125 to 1.99 micromol or mild hyper responsiveness if PD20 was between 2.00 to 6.6 micromol. PD20 of more than 6.6 micromol constitutes a negative MCT.
RESULTS: 29 patients had BCT during the study period. 19 cases were included in this review. The age ranged from 13 to 70 years old. There were 12 males and 7 females. Duration of symptoms ranged from 2 weeks to 23 years. BCT was positive (mild or moderate hyper responsiveness) in 10 out of 19 patients. No patient had high bronchial hyper responsiveness.
CONCLUSIONS: BCT is a useful adjunctive tool in the investigation of patients presenting with asthma-like symptoms. This test obviates empirical asthma treatment. BCT should be made available in all major hospitals in Malaysia.