Relationship of skin-prick reactivity to aeroallergens and hyperresponsiveness to challenges with methacholine and adenosine monophosphate

Background: Clarification of the relationship between atopy and bronchial hyperresponsiveness (BHR), both key features of asthma, is critical to our understanding of the disease. We therefore investigated the putative relationship between skin-prick reactivity to aeroallergens and BHR to direct and indirect stimuli. Methods: We performed a retrospective analysis of data from 332 patients presenting with a diagnosis of asthma. Patients were characterized by skin prick tests (SPT), spirometry and bronchial challenge with methacholine and adenosine monophosphate (AMP). Results: For patients who had BHR to methacholine but not AMP, the presence of atopy was associated with a lower PD20 (the provocative dose of methacholine producing a fall in FEV1 of 20%), amounting to a geometric mean (95% confidence interval (CI)) of 2.3-fold (1.4-4.0) difference. Furthermore, the number of skin-prick positive (SPP) responses was related to methacholine reactivity: 0-1 SPP, PD20 = 69.9 mug; 2-4 SPP, PD20 = 47.8 mug; 5-8 SPP, PD20 = 35.6 mug. There was a 2.0- fold (1.1-3.6) difference between the groups with a low (0-1 SPP) and high (5-8 SPP) degree of skin-prick reactivity. A similar pattern was seen when data were analyzed including only perennial allergens. Spirometry was unrelated to the degree of skin-prick reactivity. Discussion: These results suggest that skin-prick reactivity to aeroallergens is associated with BHR to methacholine.