Background
Irritant-induced asthma (IIA) is a rare form of occupational asthma of which long-term outcome is poorly known.
Objective
To evaluate the long-term clinical outcome of patients with IIA.
Methods
We identified 69 patients diagnosed with IIA at the Finnish Institute of Occupational Health during 2004-2018. Twenty-eight of them participated in follow-up evaluation. Median interval since 1st exposure to causal agent was 11.0 years (IQR 6.5-15.6) for participants and 15.9 years (IQR 11.7-22.0) for non-participants. Otherwise, these groups appeared comparable.
Results
| Variable | Participants (N=28) | P-value | |
| Baseline | Follow-up | ||
| Male | 26 (93%) | X | X |
| Age Mean (SD) |
46 (10.7) | 54 (9.5) | X |
| BMI, kg/m2 Mean (SD) |
28.7 (5.2) | 30.4 (6.6) | 0.014 |
| Smoking of ?10 pack years | 10 (36%) | 11 (39%) | 1.000 |
| GINA 4-5 step asthma medication | 12 (43%) | 18 (64%) | 0.754 |
| Exacerbation ?1 year | 8 (29%) | 4 (15%) | 0.375 |
| Poor symptom control1 | 13 (76%) | 11 (39%) | 0.008 |
| Non-specific bronchial hyperreactivity2 | 13 (46%) | 8 (36%) | 0.508 |
| FEV1% <80% | 8 (29%) | 6 (22%) | 1.000 |
| FeNO ?25ppb | 8 (29%) | 7 (25%) | 1.000 |
| B-Eos ?300u/l | 5 (18%) | 10 (36%) | 0.125 |
| Impaired exercise capacity in bicycle ergometry3 | X | 15 (58%) | X |
| Score of <17.1 in Newcastle laryngeal hypersensitivity questionnaire | X | 6 (23%) | X |
| Dysfunctional breathing4 | X | 7 (26%) | X |
1Asthma Control Test score of ?19 represented poor symptom control. Seventeen participants took the test at baseline
225 and 22 participants took the test, respectively
3Values of Wmax4%? 80% represented normal exercise capacity
4Score of ?23 in Nijmegen questionnaire
Conclusions
In the long-term follow-up, patients with IIA need frequently intensive medication and show poor exercise capacity. Majority of them have normal lung functions and asthma control appears to improve by time.