Assessment of inhaled corticosteroid treatment response in asthma using hypertonic histamine challenge-induced cough

Bronchial provocation tests may be utilised to monitor the efficacy of the corticosteroid treatment. Unfortunately, these measurements necessitate good patient cooperation during the spirometry. Coughing during such tests is related to the degree of the bronchoconstriction and occurs involuntarily, i.e. independent of patient cooperation. This study aimed to evaluate the utility of a hypertonic histamine challenge-induced cough in assessing the efficacy of inhaled corticosteroid treatment.

A total of 16 steroid-naïve asthmatics and 10 non-asthmatic, symptomatic controls received 800-microg beclomethasone (Beclomet Easyhaler(R), Orion Ltd., Orion Pharma, Helsinki, Finland) via powder inhaler per day for 8 weeks. Videoed inhalation challenge with hypertonic histamine solution was performed before and after the treatment. Symptom questionnaire was completed before both challenges. The airway responsiveness to hypertonic histamine was expressed as the cumulative number of coughs divided by the final histamine concentration administered [coughs/concentration ratio (CCR)] and as the provocative concentration of histamine to induce a 20% fall in FEV(1)(PC(20)).

CCR [geometric mean; 95% confidence interval (CI)] of the asthmatic subjects decreased from 494 (209-1168) to 73.6 (29.8-182) coughs per mg/mL (P = 0.002). Their PC(20) levels were 1.31 (1.07-1.60) and 1.91 (1.33-2.74) mg/mL over the treatment period (P = 0.01). The symptom frequency also decreased significantly in the asthmatics (P = 0.039). There were no significant changes in PC(20) level, in CCR level or in symptom frequency in non-asthmatic subjects during the treatment.

Hypertonic histamine challenge-induced cough and PC(20) are sensitive measures in assessing the treatment effect in asthma. The cough response may be especially useful in subjects who cannot perform spirometry reliably.