Prognostic value of methacholine challenge in patients with respiratory symptoms

The objective was to study the current clinical status of 78 adults with respiratory symptoms, who were referred 3 to 10 years ago for diagnostic methacholine challenge. We tested the hypothesis that methacholine hyperresponsiveness would be associated on follow-up with increased symptoms of chest tightness, dyspnea, wheezing, cough, and more frequent use of selected treatment modalities.

Current symptoms were evaluated by means of interview questionnaire, and methacholine challenge was repeated during follow-up examination. Comparisons were made between patients who were and those who were not hyperresponsive to methacholine at initial and follow-up challenges by using specific symptoms and calculated symptom and treatment scores.

We found that subjects who had positive methacholine challenge results on initial challenge (n = 37) were significantly more likely than those with negative results (n = 41) to have nonexertional chest tightness, wheezing, and dyspnea, but not cough. A high proportion of both groups had current symptoms. Two thirds of the patients continued to have positive (n = 25) or negative (n = 27) methacholine challenge results, and one third had a change in status (n = 26). Significant correlations were also found between follow-up methacholine responsiveness and concurrent symptoms, again with the exception of cough.

Methacholine challenge warrants cautious interpretation in the individual patient as an aid to diagnosis and prognosis in the evaluation of respiratory symptoms, especially cough.