Occupational Asthma, Diagnosis & Classification

Diagnosis and classification of work-related asthma, distinguishing sensitizer-induced occupational asthma (immunologic, with a latency period) from irritant-induced asthma/RADS (non-immunologic, no latency) and work-exacerbated asthma. Emphasizes objective confirmation (serial peak flow at and away from work, specific inhalation challenge) and the central management principle: complete removal from the causative exposure, not mere reduction.

Evidence tier: Guideline-derived.

Decision points

  • Did asthma begin with or without latency?
  • Is the diagnosis objectively confirmed?

Do-not-miss pitfalls

  • Complete REMOVAL from exposure, not reduction, is required for sensitizer-induced OA. Continued low-level exposure (even with respirators) usually allows progressive decline in lung function. This is the single most important management principle and distinguishes OA from work-exacerbated asthma.
  • Diagnose OA objectively, not on history alone, the diagnosis ends careers and triggers compensation. Serial peak flow at and away from work is the practical first-line objective test; specific inhalation challenge is the reference standard.
  • A negative specific IgE/skin test does NOT exclude OA, low-molecular-weight agents (isocyanates, anhydrides, persulfates, metals) frequently act through non-IgE mechanisms. Immunologic tests confirm HMW-agent OA but cannot rule out LMW-agent OA.
  • The earlier exposure stops after symptom onset, the better the prognosis, delayed diagnosis worsens outcomes. Persistent exposure after symptoms begin predicts incomplete recovery.
  • Distinguish the three patterns: sensitizer-induced OA (latency, work caused it), irritant-induced/RADS (no latency, single high exposure), and work-exacerbated asthma (pre-existing asthma worsened by work). They differ in mechanism, testing, and whether the worker must leave the job.
  • Isocyanates (spray painting, polyurethane) are the most common LMW cause of OA in industrialized settings, and specific IgE is positive in only a minority. Maintain suspicion despite negative immunologic tests.
  • Symptoms improving on weekends/holidays and worsening across the work week is a classic but imperfect clue, by the time fixed airflow obstruction develops, the work-relatedness pattern may be lost.
  • OA is frequently missed in adult-onset asthma, always take an occupational history in any working-age adult with new asthma. Screen co-workers when a sensitizer-induced case is confirmed.

Evidence & citations

  1. Tarlo SM, Lemiere C. Occupational asthma. N Engl J Med. 2014;370(7):640-649. PMID 24521110
  2. Baur X, Sigsgaard T, Aasen TB, et al. Guidelines for the management of work-related asthma. Eur Respir J. 2012;39(3):529-545. PMID 22379148
  3. Vandenplas O, Wiszniewska M, Raulf M, et al. EAACI position paper: irritant-induced asthma. Allergy. 2014;69(9):1141-1153. PMID 24854136
  4. Tarlo SM, Balmes J, Balkissoon R, et al. Diagnosis and management of work-related asthma: American College of Chest Physicians Consensus Statement. Chest. 2008;134(3 Suppl):1S-41S. PMID 18779187

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.