AIRWAY HYPERRESPONSIVENESS AND COUGH-RECEPTOR SENSITIVITY IN CHILDRENWITH RECURRENT COUGH

In children, recurrent cough is a common presenting symptom that may r epresent asthma. We tested the hypotheses that children with recurrent cough have increased cough-receptor sensitivity (CRS) or airway hyper responsiveness (AHR). Skin prick testing, the capsaicin CRS test, and hypertonic saline (HS) challenge were performed in 44 children (median age: 8.9 yr) with recurrent dry cough (greater than or equal to 2 epi sodes of cough, each lasting greater than or equal to 2 wk, within a p eriod of 12 mo) and 44 controls. Measures of CRS were the concentratio n of capsaicin required to stimulate greater than or equal to 2 coughs (Cth) and greater than or equal to 5 coughs (C5). During the coughing period, Cth (mean log: 0.62 [95% CI: 0.43 to 0.81]) and C5 (mean log: 1.15 [95% CI: 0.86 to 1.44]) of the subjects without AHR were signifi cantly lower (p = 0.0026, 0.027, respectively) than Cth (mean log: 1.2 7 [95% CI: 0.88 to 1.66]) and C5 (mean log: 1.79 [95% CI: 1.21 to 2.37 ]) of the subjects with AHR and those of the controls (p = 0.0002 and 0.0001). During the cough-free period, there was no difference in CRS among the groups. In subjects who demonstrated AHR, the provocation do se causing a greater than or equal to 15% fall in FEV1 (PD15) during t he cough period was significantly lower (p = 0.005) than that during t he cough-free period. We conclude that AHR or increased CRS is present during the coughing phase in children with recurrent cough.