Occupational Asthma Reference

Beach J, Rowe BH, Blitz S, Crumley E, Hooton N, Russell K, Spooner C, Klassen T., Diagnosis and Management of Work-Related Asthma, AHRQ Publication No. 06-E003-2. Rockville, 2005;-:1-107,

Keywords: guideline,canada,NSBR, IgE,PEF,Challenge

Known Authors

Jeremy Beach, University of Alberta Jeremy Beach

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Approximately 5 to 15 percent of adult onset asthma is thought to be occupational asthma (OA).

To systematically review literature regarding the diagnosis and management of OA,and specifically, to compare specific inhalation challenge testing (SIC) with alternative tests, and to review management, including reduction or cessation of exposure.

Search Strategy
Electronic databases and trials registries were searched. Additional references were identified by bibliographic searches of included studies, hand searches of conference proceedings, and contact with authors.
Selection Criteria: Population: De-novo OA or a previous diagnosis of asthma that was exacerbated at work. Study design: Controlled clinical trials, prospective or retrospective cohort, cross-sectional, case-series. Diagnosis: Intervention: At least two diagnostic tests, including one
or more from a pre-determined hierarchy of ‘reference standard’ tests.

2 x 2 or 2 x 1 table, sensitivity, specificity, likelihood ratios, time to diagnosis, cost of diagnosis, and adverse effects. Management: Intervention: Pharmacological treatment, removal, reduced, or continued
exposure. Outcomes: Pulmonary function, medication use, quality of life, symptoms, economic consequences, and adverse events.

Data Extraction
Two researchers independently extracted data.

Data Analysis
Diagnosis: Pooled sensitivities and specificities for sensitizer-induced OA with 95% confidence intervals (CI) were derived using a random effects model. Management: Weighted pooling of means and standard deviations to combine results within studies. Quantitative analysis was not conducted due to heterogeneity.

Main Results
One-hundred and twenty-four unique diagnostic studies and 65 unique
management studies were included. Much of the evidence relates to sensitizer induced OA. Diagnosis: Among the high molecular weight (HMW) asthmagens compared to SIC, nonspecific bronchial provocation (NSBP) test, skin prick test (SPT), and serum specific IgE had sensitivities above 73 percent. The specificity was highest between serum specific IgE versus
SIC (79.0 percent [95% CI: 50.5 to 93.3 percent]). The highest sensitivity among low molecular weight (LMW) asthmagens occurred between SPT and SIC (72.9 percent [95% CI: 59.7 to 83.0 percent]), but this applied only to LMW sensitizers for which SPT could be performed. When compared to SIC, serum specific IgE and SPT had similar specificities (88.9 percent [95% CI:
84.7 to 92.1 percent] and 86.2 percent [95% CI: 77.4 to 91.9 percent], respectively). For HMW asthmagens, a combined positive test result to NSBP test and SPT versus SIC yielded modest sensitivity (60.6 percent [95% CI: 21.0 to 89.9 percent]) yet high specificity (82.5 percent [95% CI: 54.0 to 95.0 percent]). Management: Removed workers showed improved lung function and decreased non-specific broncial responsiveness at follow-up; exposed workers were either no better or worse. Lack of data prevented conclusions about the effectiveness of reducing exposure. Removed workers suffered from reduced income and/or unemployment. Fully or partially exposed workers also appeared to have reduced earnings over time.

Diagnosis: Single NSBP test, specific SPT, or serum specific IgE testing alone is insufficient to diagnose OA. While positive results would increase the likelihood of OA, a negative result would not exclude OA. The literature supports the concept of combined testing; however, additional research is required to determine which combination of tests would result in sufficient sensitivity and specificity that it could replace SIC. Management: OA appears to be slow to resolve, and may worsen irrespective of subsequent exposure status. Patients who are removed from the workplace rarely experience complete resolution, may require medications, and experience continued airflow limitation. Standard treatments for asthma appear to be effective in OA; however, there is limited research.

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