Changes in exhaled nitric oxide after inhalation challenge with occupational agents

Background and objective: the use of fractional exhaled nitric oxide (feno) concentration has been proposed as a surrogate marker for monitoring airway response to specific inhalation challenge (sic). we investigated the usefulness of feno measurements for monitoring airway response to sic with occupational agents. material and methods: workers with suspected occupational asthma were recruited to undergo sic with occupational agents and subsequently feno testing at baseline and 24 hours. results: sixty-eight patients were evaluated,45 of whom had a positive sic. sic-positive patients showed a significant increase in feno 24 hours postchallenge,with an increase ratio of 1.25 (95% ci,1.05-1.48; p=.01); no increase was seen in patients with a negative sic (p=.08). the predictive capacity of variations in feno showed that for each unit increase in feno,the probability of a positive sic rose by 4%. a baseline feno value of 25 ppb predicted a positive sic with 60% sensitivity and 80% specificity. the increase in %feno cutoff point providing maximal sensitivity and specificity for predicting a positive sic was 41% (sensitivity 50%,specificity 95%). conclusions: we demonstrated that asthmatic reactions induced by occupational agents during sics are associated with a consistent increase in feno. however,the predictive diagnostic capacity of feno measurements is low. while feno may aid in the interpretation of sic in some cases,it cannot be used as a general surrogate marker to predict or to assess sics with occupational agents. © 2013 esmon publicidad.