Measurement Characteristics of Peak Expiratory Flow* Christina A. Holcroft, ScD; Ellen A. Eisen, ScD; Susan R. Sama, ScD; and David H. Wegman, MD Study objectives: To evaluate features of the peak expiratory flow (PEF) test protocol, and to characterize patterns of reproducibility in multiple PEF measurements. Design: Cross-sectional study. Setting: University population. Participants: Two hundred twenty-three healthy adults. Interventions: Participants recorded five PEF measurements in each of five sessions per day for 1 week. Measurements and results: Patterns of within-session variability were characterized using a reproducibility criterion based on a large percentage difference between best trials and evidence of a maneuver-induced bronchospasm (MIB) indicated by successive drops of PEF values in a session. Although the maximum PEF value in a session occurred on the fourth or fifth trial 32% of the time, the change in PEF values was small. Supervision was associated with small improvements in level and reproducibility. Using a cutoff of 5% for defining reproducibility, 15% of all sessions were not reproducible. When averaged over each subject, 9% of the cohort had a mean difference > 5%. Overall, MIB was unusual and observed in 8% of all test sessions; however, MIB was more common among asthmatics and subjects with wheeze, atopy, or allergies than subjects without. By contrast, poor reproducibility was more common among smokers and subjects with cough and phlegm. Conclusions: These results illustrate that it may be unnecessary to supervise all sessions or collect more than three efforts. Results also suggest that reproducibility reflects smoking-related abnormalities, whereas MIB may reflect airways hyperresponsiveness. (CHEST 2003; 124:501–510) Key words: asthma; bronchial spasm; epidemiologic methods; peak expiratory flow; reproducibility of results; respiratory hypersensitivity Abbreviations: ATS = American Thoracic Society; MIB = maneuver-induced bronchospasm; PEF = peak expiratory flow I ncreases in asthma prevalence and mortality dur- ing the past decade have led clinicians and epide- miologists to direct more attention to peak expiratory flow (PEF). The increased diurnal variation in PEF, characteristic of asthmatics, has been interpreted as evidence of the increased variability in airway cali- ber— bronchial hyperresponsiveness—which is the predominant physiologic feature of the disease. Findings of Boezen et al, 1 Higgins et al, 2 Neukirch et al, 3 and Quackenboss et al 4 present a consistent picture in which diurnal amplitude is a marker not only for asthma, but also for the degree of hyperre- sponsiveness even among nonasthmatics. The greater circadian variation in PEF suggests that biological variability within test may be at least as large for PEF as for FEV 1 . Excessive variability in FEV 1 has been shown to be a good indicator of respiratory difficulty, even in the absence of asthma. 5– 8 One of our goals was to find patterns of short-term variability that contain physiologic information. An- other aim was to evaluate within-session variability in a relatively unexposed adult population of both asthmat- ics and nonasthmatics, in order to provide a framework for epidemiologic studies of environmental or occupa- tional hazards. *From the University of Massachusetts (Drs. Holcroft, Eisen, and Wegman), Lowell; and the Harvard School of Public Health (Dr. Sama), Boston, MA. This study was supported by National Institutes of Health grant 1-R01-HL51975. Manuscript received August 8, 2001; revision accepted February 14, 2003. Reproduction of this article is prohibited without written permis- sion from the American College of Chest Physicians (e-mail: permissions@chestnet.org). Correspondence to: Christina Holcroft, ScD, Work Environment Department, UMass Lowell, One University Ave, Lowell, MA, 01854; e-mail: Christina_Holcroft@uml.edu www.chestjournal.org CHEST / 124 / 2 / AUGUST, 2003 501 Downloaded From: http://journal.publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21997/ on 04/03/2017