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Original Research: ASTHMA |

A New Diagnostic Score for Occupational Asthma: The Area Between the Curves (ABC Score) of Peak Expiratory Flow on Days at and Away From Work

Vicky C. Moore, MS; Maritta S. Jaakkola, MD; Cedd B. S. G. Burge, MS; Alastair S. Robertson, MD; Charles F. A. Pantin, MD; Arun Dev Vellore, MD; P. Sherwood Burge, MD
Author and Funding Information

*From the Occupational Lung Disease Unit (Mrs. Moore, Dr. Jaakkola, Mr. C. Burge, Dr. Robertson, Dr. Vellore, and Dr. P. Burge), Heart of England NHS Trust, Birmingham Heartlands Hospital, Birmingham, UK; Institute of Occupational and Environmental Medicine, University of Birmingham, Birmingham, UK; Respiratory Medicine Unit, Institute of Clinical Sciences, University of Oulu, Oulu, Finland; Department of Occupational Health, Selly Oak Hospital, Birmingham, UK; and Department of Respiratory Medicine (Dr. Pantin), University Hospital of North Staffordshire, Stoke on Trent, UK.

Correspondence to: Vicky Moore, MS, Occupational Lung Disease Unit, Department of Respiratory Medicine, Birmingham Heartlands Hospital, Bordesley Green East, Birmingham, B9 5SS UK; e-mail: vicky.c.moore@heartofengland.nhs.uk


This project was funded by a PhD fellowship from the COLT Foundation.

Drs. Burge, Vellore, and Robertson have no conflicts of interest to disclose. Dr. Jaakkola has received some travel awards for scientific meetings from GlaxoSmithKline and MSD. Mrs. Moore received COLT fellowship funds for her part-time PhD, of which this research forms a part. The work is presented at international and national meetings and spoken about in smaller groups as part of teaching about the diagnosis of occupational asthma.

Dr. Burge promotes and disseminates the use of serial measurements of peak expiratory flow for the diagnosis of occupational asthma. His department receives some monies from grants, donations, and legal fees to support the research. He has no personal financial interest. Dr. Pantin has published on the subject of OASYS software to enhance its reputation, and otherwise has no conflict of interest relating to this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).


Chest. 2009;135(2):307-314. doi:10.1378/chest.08-0778
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Background:  Evidence-based guidelines recommend serial measurements of peak expiratory flow (PEF) on days at and away from work as the first step in the objective confirmation of occupational asthma. The aim of this study was to improve the diagnostic value of computer-based PEF analysis by using the program Oasys-2 to calculate a score from the area between the curves (ABC) of PEF on days at and away from work.

Methods:  Mean 2-hourly PEFs were plotted separately for workdays and rest days for 109 workers with occupational asthma and 117 control asthmatics. A score based on the ABC was computed from records containing ≥ 4 day shifts, ≥ 4 rest days, and ≥ 6 readings per day. Patients were randomly classified into two data sets (analysis and test sets). Receiver operator characteristic (ROC) curve analysis determined a cutoff point from set 1 that best identified those with occupational asthma, which was then tested in set 2.

Results:  Logistic regression analysis showed that all ABC PEF scores were significant predictors of occupational asthma, with the best being ABC per hour from waking (odds ratio, 11.9 per 10 L/h/min; 95% confidence interval, 10.8 to 13.1). ROC curve analysis showed that a difference of 15 L/min/h provided a high specificity without compromising sensitivity in diagnosing occupational asthma. Analysis of data set 2 confirmed a specificity of 100% and sensitivity of 72%.

Conclusion:  The ABC PEF score is sensitive and specific for the diagnosis of occupational asthma and can be calculated from a shorter PEF surveillance than is needed for the current Oasys-2 work effect index.

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