COMPARISON OF HISTAMINE AND ACETYLCHOLINE FOR USE IN BRONCHIAL CHALLENGE TESTING IN ATOPIC AND NONATOPIC SUBJECTS WITH CHRONIC AIRWAYS OBSTRUCTION - A REVIEW OF 180 CASES

A retrospective study was performed to evaluate the diagnostic yield for bronchial hyperresponsiveness from histamine and acetylcholine challenge tests. The records of 180 cases from the last 10 years were analysed. They were selected because their hyperresponsiveness to inhaled histamine or acetylcholine was equal or less than 32 mg . ml-1. Increasing doses of histamine and acetylcholine were given up to a maximum of 32 mg . ml-1 according to the method of de Vries et al. [3]. The challenges were accomplished on two separate days. The provocative dose of agonist causing a 20% fall in FEV1 (PC20) was noted. The interrelationships between smoking history, objective markers of allergy, patient's complaints, histamine and acetylcholine responsinevess were examined. Separate statistical analyses are presented for atopic and nonatopic subjects with chronic airways obstruction. More subjects had a measurable PC20 with acetylcholine than with histamine (43 vs. 16 subjects, p <0.0001). Using the chi2 test, the relationship between PC20 histamine and PC20 acetylcholine was similar in smokers and nonsmokers, and in atopics and nonatopics. It is concluded that for an equal molar basis, acetylcholine evokes a higher frequency of bronchus obstruction than histamine in patients.