Cough Reflex Sensitivity Test. Cough reflex sensitivity (log10 [C5]) to citric acid in chronic cough patients was performed using an ascending dose (0.03 – 4 M) with three additional randomly interspersed placebo (normal saline) controls. The number of coughs was counted by an experienced observer and the test was stopped after the concentration of citric acid eliciting at least 5 consecutive coughs (C5) was reached. Log transformed data are presented with error bars indicating mean +/− S.E.M. Reflex sensitivity was not significantly different between lymphocytic and non-lymphocytic patient groups (Student’s T-test).