Long-term prognosis of work-related asthma after specific inhalation challenge.

Abstract

Few studies have assessed the long-term prognosis of work-related asthma (WRA). We evaluated outcomes in WRA patients after specific inhalation challenge (SIC), including remission rates and factors associated with poor outcomes. Cases with positive SIC were diagnosed as occupational asthma. A follow-up questionnaire was sent to 618 WRA patients. Difficult-to-treat asthma was defined as poor symptom control, ≥2 asthma exacerbations or ≥1 serious exacerbation within a year despite treatment with GINA step 4-5 asthma medication. Clinical asthma remission off-treatment was defined as no symptoms, exacerbations or medication within a year. Altogether 274 (44%) WRA patients responded a median of 8.5 years after SIC; 110 had positive and 164 negative SIC reaction. Among responders, 216 (79%) reported no current exposure to the suspected causal agent, and 173 (75%) of working-aged patients reported being in work life. Seventy (67%) SIC positive and 75 (47%) SIC negative patients had changed their occupations (p=0.002). Eighty-seven (32%) had difficult-to-treat asthma and 12 (4%) had clinical asthma remission off-treatment, with no significant differences between SIC positive and negative groups. Factors predicting difficult-to-treat asthma at follow-up included age ≥ 45.8 years (adjusted OR 2.10, 95% CI 1.19-3.70), Asthma control test score < 20 (OR 2.02, 1.13-3.61), GINA step 4-5 medication (OR 3.10, 1.68-5.71), and difficult-to-treat asthma (OR 5.73, 2.66 - 12.35) at diagnosis. Long-term outcomes are largely comparable in WRA patients regardless of SIC results. Clinical asthma remission is rare. The patients with poorly controlled asthma at diagnosis require close follow-up and support.