Comparison of peak expiratory flow variability between workers with work-exacerbated asthma and occupational asthma.
BACKGROUND
Peak expiratory flow (PEF) monitoring is frequently used to diagnose occupational asthma (OA). The variability of PEF between periods at work and away from work has not been described in workers with work-exacerbated asthma (WEA). We sought to assess and compare the diurnal variability of PEF during periods at and away from work between subjects with OA and WEA.


METHODS
Workers referred for work-related asthma underwent PEF monitoring for 2 weeks at and away from work. The diagnostic of OA or WEA was subsequently made according to the respective positivity or negativity of the specific inhalation challenges. PEF mean diurnal variability was calculated during periods at and away from work. PEF graphs were also interpreted using direct visual analysis by five observers and using a computer program (Oasys-2, Expert System ) [available at: http://www.occupationalasthma.com].


RESULTS
Thirty-four subjects were investigated (WEA, n = 15; OA, n = 19). There was a greater variability of PEF at work than away from work in both OA (19.8 +/- 8.7% vs 10.7 +/- 6.3%, p < 0.001) and WEA (14.2 +/- 4.8% vs 10.6 +/- 5.6%, p = 0.02). However, the magnitude of the variability was higher in OA than in WEA (p = 0.02). The visual interpretation of PEF or the Oasys-2 program failed to distinguish WEA from OA.


CONCLUSIONS
Although workers with OA showed a higher PEF variability than workers with WEA when at work, clinicians were unable to reliably differentiate OA from WEA using the visual interpretation of PEF graphs or the computerized analysis.
Chiry
Samah
S
Department of Chest Medicine, Sacré-Coeur Hospital, 5400 Gouin West, Montreal, QC, Canada.
Cartier
André
A
Malo
Jean-Luc
JL
Tarlo
Susan M
SM
Lemière
Catherine
C
D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D016273:Occupational Exposure / Q000009:adverse effects*; D010366:Peak Expiratory Flow Rate / Q000502:physiology*; D011379:Prognosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods; D012307:Risk Factors; D012720:Severity of Illness Index