Responsiveness to three bronchial provocation tests in patients with asthma.

STUDY OBJECTIVES To compare a new bronchial provocation test, the mannitol challenge, with cold air and histamine challenges to demonstrate airway hyperresponsiveness (AHR) in patients with difficult-to-diagnose asthma. DESIGN A prospective study. PARTICIPANTS Thirty-seven consecutive patients with recently diagnosed, steroid-naive, mild, or atypical asthma fulfilling the diagnostic criteria of Finnish Social Insurance Institution, and 10 healthy control subjects. INTERVENTIONS Each subject completed a symptom questionnaire and underwent spirometry, diffusion capacity measurement, skin-prick tests, and bronchial provocations with mannitol, histamine, and cold air. The severity of asthma was classified according to the Global Initiative for Asthma (GINA). RESULTS Fifty-one percent of the asthmatic patients responded to mannitol (> or =15% fall in FEV(1)), 24% to cold air (> or =9% fall in FEV(1)), and 81% or 49% to histamine (provocative dose causing a 15% fall in FEV(1) [PD(15)] < 1.0 mg or < 0.4 mg, respectively). None of the healthy control subjects responded. The GINA classification was not associated with responsiveness to any of the challenges. CONCLUSIONS Mannitol is more sensitive than cold air in demonstrating AHR in patients with mild or atypical asthma. Histamine was more sensitive than both mannitol and cold air if 1.0 mg was used as a cut-off value for histamine PD(15). However, if the cut-off value for histamine PD(15) is lowered to 0.4 mg, which represents a specific diagnosis of asthma according to previous studies, the sensitivity values of mannitol and histamine challenges are comparable.