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Specificity of Specific Inhalation Challenge with Non-Standard Occupational Agents in Consecutive Pa
Senin, 01 Okt 2018 13:41:36


Introduction: Specific inhalation challenge (SIC) is the reference standard for the diagnosis of occupational asthma, however the significance of a positive test is doubtful unless work exposure causes measurable changes in lung function. We have used Oasys analysis of serial PEF at home and work (with a specificity of >90%) to identify occupational asthma, and have used these to validate the specificity of SIC testing with non-standard agents.

Methods: This is a retrospective survey of all workers with positive SIC to occupational agents contributing to the EAACI survey. They were asked to measure PEF 2-hourly from waking to sleeping for 4 weeks before SIC testing with realistic exposures. Inadequate PEF records were repeated. The hourly patterns of response were compared between SIC and PEF record.

Results: 52 consecutive workers with positive SIC to a wide range of mostly unusual occupational agents were included. Records suitable for Oasys analysis were obtained in 48/52, 14 requiring >1 attempt. 48/48 confirmed occupational work-related changes in PEF by at least 1 of the Oasys evaluations (Oasys score, ABC or timepoint). There was a strong association between the timings of response at work and during SIC (χ2 =15 p<0.001), Table 1.

Table 1.

Relationship between pattern of reaction at work from serial PEFs and SIC.

SIC reaction
Oasys pattern (unclassifiable in 3) Immediate or dual Late or dual
Immediate or flat 24 6
Late 3 12

Conclusion: Positive SIC testing with realistic occupational exposures does not produce false positive tests in our hands, and has identified many unusual and novel causes of occupational asthma.