Chest
Volume 100, Issue 1, July 1991, Pages 63-69
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Clinical Investigations
Peak Expiratory Flow Rates in Possible Occupational Asthma

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Objective criteria for interpretation of peak expiratory flow rate readings were assessed in 50 patients evaluated for suspected occupational asthma who had at least two weeks of PEFR readings and an objective diagnosis based on other investigations. The prevalence of OA was 36 percent. Peak flows were interpreted by two observers blinded to other results. Criteria for a PEFR interpretation of OA were as follow: diurnal variation ≥20 percent relatively more frequently or with greater variation on working days than days off work. With the objective diagnoses as the gold standard, the sensitivity of the PEFR interpretations was 72 percent for OA; specificity for no asthma was 53 percent. Excluding those with ≥20 percent variation on only one day sensitivity improved to 93 percent for OA, and specificity to 77 percent. There was an acceptable level of interobserver variation (kappa 62 to 83 percent). We conclude that simple objective criteria for PEFR interpretation can be developed with acceptable interobserver variation.

Section snippets

Materials and Methods

Patients were selected from the files of consecutive workers referred for assessment of possible occupational asthma. They were all seen in the occupational asthma clinics of the Cage Research Institute and the Toronto General Hospital between 1978 and 1988 by one of us (S.M.T.) using the same diagnostic approach throughout, as previously described.10

A full history of all subjects included occupational exposure, information on any known spills or unusually high exposures, respiratory symptoms,

Demographic Characteristics

The demographic characteristics are summarized in Table 1; the majority of the patients were men, about one half were atopic, and isocyanates were the most frequent exposure agent. All patients had a history consistent with occupational asthma. The prevalence of OA (based on the objective diagnoses) was 18 (36 percent) among the 50 eligible patients. Consensus discussion was needed to settle initial disagreement between the observers for 12 of the 50 records. Table 2 shows the overall

Discussion

This study has demonstrated that explicit criteria for the interpretation of peak flow tracings can be developed with acceptable interobserver variation, as demonstrated by the moderately high kappa values.

ACKNOWLEDGMENTS

The authors thank Drs. I. Broder and G. J. Stopps for their helpful comments.

References (20)

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Manuscript received May 11; revision accepted November 12.

From the Health Studies Service, Ontario Ministry of Labour, University of Toronto, Toronto, Canada

Gage Research Institute and Toronto General Hospital

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