A systematic review of the diagnosis of occupational asthma

Background: This study systematically reviews literature regarding the diagnosis of occupational asthma (OA) and compares specific inhalation challenge (SIC) testing with alternative tests. Methods: Electronic databases and trials registries were searched; additional references were identified from bibliographic searches of included studies, hand searches of conferences, and author contacts. Various study designs (clinical trials, cohorts, cross-sectional, or case series) were included involving workers with suspected OA. All diagnostic tests were compared to a "reference standard," and two researchers independently extracted 2 X 2 data. Pooled sensitivities and specificities (95% confidence intervals [CIs]) were derived. Results: Seventy-seven studies were included. For high molecular weight (HMW) agents, the nonspecific bronchial provocation (NSBP) test, skin-prick test (SPT), and serum-specific IgE had sensitivities > 73% when compared to SIC. Specificity was highest for specific IgE vs SIC (79.0%; 95% CI, 50.5 to 93.3%). The highest sensitivity among low molecular weight asthmagens occurred between combined NSBP and SPT vs SIC (100%; 95% CI, 74.1 to 100%). When compared to SIC, specific IgE and SPT had similar specificities (88.9%; 95% CI, 84.7 to 92.1%; and 86.2%; 95% CI, 77.4 to 91.9%, respectively). For HMW agents, high specificity was demonstrated for positive NSBP tests and SPTs alone (82.5%; 95% CI, 54.0 to 95.0%) or when combined with specific IgE (74.3%; 95% CI, 45.0 to 91.0%) vs SIC. Sensitivity was somewhat lower (60.6% and 65.2%, respectively). Conclusions: In appropriate clinical situations when SIC is not available, the combination of a NSBP test with a specific SPT or specific IgE may be an appropriate alternative to SIC in diagnosing OA. While positive results of single NSBP test, specific SPT, or serum-specific IgE testing would increase the likelihood of OA, a negative result could not exclude OA.