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

BACKGROUND: Few studies have assessed the long-term prognosis of work-related asthma (WRA). OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.