The temporal relationship between increases in airway responsiveness to histamine and late asthmatic responses induced by occupational agents.

The temporal relationship between increases in airway responsiveness and the late asthmatic response was assessed in nine patients challenged with occupational agents toluene diisocyanate (one patient), carmine (one patient), maleic anhydride (two patients), colophony (four patients), and trimellitic anhydride (one patient). The provocation concentration of histamine causing a 20% decrease in FEV1 (PC20) was measured before challenge and at approximately 3 hours and 24 hours on control and active-challenge days. Thirteen active challenges provoked eight definite late asthmatic responses (maximum fall in FEV1 greater than 15% at 3 to 11 hours). At 3 hours after the challenges that provoked late responses, there was a significant (p less than 0.02) decrease in PC20 that was more (p less than 0.03) than that observed for the five tests provoking early (late FEV1 fall 0% to 5%) or equivocal late (FEV1 fall 6% to 15%) responses. At 24 hours, PC20 remained decreased (p less than 0.05), although it was less so than at 3 hours (p less than 0.05) and not significantly when compared with challenge tests causing single early or equivocal late responses. The 3-hour decreases in PC20 were identified when FEV1 (five of seven observations) was greater than 90% of prechallenge values. For the nine independent tests, the 3-hour decreases in PC20 correlated (r = 0.72; p less than 0.05) with the magnitude of the late falls in FEV1, whereas this was not observed at 24 hours (r = 0.35; p, not significant).(ABSTRACT TRUNCATED AT 250 WORDS)