Avoidance therapy in reactive dye—induced occupational asthma: long-term follow-up

Background

Previous studies reported that early diagnosis and avoidance therapy are the most important factors for prevention of permanent lung impairment; however, few studies have evaluated the long-term prognosis of reactive dye—induced occupational asthma (RD-OA).

Objective

To evaluate the long-term outcomes of RD-OA.

Methods

Methacholine airway hyperresponsiveness (AHR) and lung functions were evaluated and compared in 26 patients with RD-OA at the time of diagnosis and after complete avoidance of the causative agents. Patients with continued (n = 13) or remitted (n = 6) AHR were further monitored for up to a mean ± SD of 8.7 ± 1.8 years.

Results

The AHR resolved in 10 (38%) of 26 patients a mean ± SD of 2.2 ± 1.3 years after complete avoidance of RDs; however, prebronchodilator forced expiratory volume in 1 second (FEV₁) values were not different. Levels of IgE specific to the RD–human serum albumin complex were markedly decreased at first follow-up in 5 RD-atopic patients from whom paired serum samples were compared (P = .02). The AHR disappeared in an additional 5 patients and improved in 4 by the second follow-up. The FEV₁ values also improved compared with diagnosis and first follow-up levels. Favorable prognosis was associated with early diagnosis of RD-OA and complete avoidance of the causative agent. No association was found with smoking history, latent periods, the presence of RD specific IgE, baseline provocation concentration that caused a decrease in FEV₁ of 20%, or FEV₁.

Conclusions

Early diagnosis and avoidance therapy are the most important prognostic factors in RD-OA. The AHR and lung function of patients with RD-OA can sometimes be recovered steadily and slowly through avoidance measures.