USE AND SAFETY OF A SHORTENED HISTAMINE CHALLENGE TEST IN AN OCCUPATIONAL STUDY

A shortened histamine challenge test was used in a study of occupation al airway disease. We evaluated the safety, defined as the absence of a decrease in forced expiratory volume in one second (FEV1) of greater than 40%. The occurrence of complaints, the repeatability of test res ults, and the average amount of time saved were measured. A standard p rotocol was used comprising 30 s tidal breathing with sequential doubl ing concentrations from 1 to 32 mg . ml(-1) histamine, Subjects with n o indication of hyperresponsive airways started at 4 mg . ml(-1). If t he decrease in FEV1 was <6%, a concentration step was skipped (fourfol d increase in concentration), The test was terminated when the decreas e in FEV1 was at least 18%. A total of 697 subjects performed a test. All subjects with a provocative concentration of histamine producing a 20% decrease in FEV1 (PC20) value of less than or equal to 4 mg . ml( -1) (n=16) started at the lowest concentration. Six subjects reached a greater than or equal to 20% decrease in FEV1 (range 21-24%) after a fourfold increase in concentration, Five subjects had a decrease in FE V1 of greater than 40%, and this decrease occurred after a doubling co ncentration, Cough, flushing, and chest tightness were noted in 18% of the subjects, In 56% of the tested subjects, the shortest provocation scheme (phosphate solution followed by 4, 16 and 32 mg . ml(-1) hista mine) was applied, resulting in a time reduction of nearly 50% per tes t, and reducing the time needed to complete the study from 5 to 3 mont hs. The shortened test was repeatable within one concentration differe nce. We conclude that, in this occupational setting, the histamine cha llenge test can be shortened to save time without risk of excessive fa lls in FEV1.