Abstract

Serial peak expiratory flows (PEF) are a cheap and effective way to confirm the diagnosis of occupational asthma. Records are susceptible to fabrication and poor quality. There is a trade off between accepting only blows fulfilling quality standards with reduced data quantity and accepting all blows irrespective of quality. We have investigated the effect of systematically reducing quality on the diagnostic sensitivity and specificity using the Oasys system.

Methods
PEF measurements from 36 specific inhalation challenge positive workers and 44 non-occupational asthmatics were used. Every PEF measurement was randomly changed to be up to +50L/minor-50L/min from the original value in increments of 10L/min. Records were randomised 3 times and compared at each randomisation to the original using the Oasy sscore ,area between curves (ABC) score and timepoint analysis.

Results
The table shows how the sensitivity and specificity changed at each randomisation after data corruption.

Sensitivity and (Specificity) of Oasys score at randomisations 0, 1, 2 and 3 respectively was 75(84), 67(73), 72(68), 86(86)

Sensitivity and (Specificity) of ABC score was 69(93), 61(89), 55(86), 69(93)

Sensitivity and (Specificity) of Timepoint analysis was 64(84), 58(84), 44(86), 55(86)

Conclusion
The sensitivity and specificity for diagnosing occupational asthma was little affected by reducing data quality using Oasys analyses. This suggests that data quality is less important than quantity in this situation.

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