Use and safety of a shortened histamine challenge test in an occupational study

A shortened histamine challenge test was used in a study of occupational 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 results, and the average amount of time saved were measured. A standard protocol was used comprising 30 s tidal breathing with sequential doubling concentrations from 1 to 32 mg.ml-1 histamine. Subjects with no indication of hyperresponsive airways started at 4 mg.ml-1. If the decrease in FEV1 was < 6%, a concentration step was skipped (fourfold increase in concentration). The test was terminated when the decrease 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 < or = 4 mg.ml-1 (n = 16) started at the lowest concentration. Six subjects reached a > or = 20% decrease in FEV1 (range 21-24%) after a fourfold increase in concentration. Five subjects had a decrease in FEV1 of greater than 40%, and this decrease occurred after a doubling concentration. 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 histamine) was applied, resulting in a time reduction of nearly 50% per test, and reducing the time needed to complete the study from 5 to 3 months. The shortened test was repeatable within one concentration difference.(ABSTRACT TRUNCATED AT 250 WORDS)