BACKGROUND:In pediatric cystic fibrosis (CF) ambulatory care, handheld spirometry in individual clinic rooms would improve patient flow and potentially reduce patient-to-patient contact. A validation study was conducted to examine the accuracy of an entirely handheld turbine spirometer vs a standard laboratory device in pediatric CF patients. METHODS:Spirometric data were obtained from 76 CF patients aged less than 18 years in the ambulatory setting using the Micro Loop Spirometer (CareFusion) and compared to same-day data from conventional laboratory spirometry. RESULTS:Linear relationships were obtained between devices, demonstrating good correlation: r = .99, .99, .97, and .82 for forced expiratory volume in 1 second (FEV1) , forced vital capacity (FVC), FEF25%-75% , and peak expiratory flow, respectively (P < .001 for all). Biases (mean differences between devices) were -65 mL for FEV1 (P < .001) and -115 mL for FVC (P < .001) on the handheld. Bland-Altman plots demonstrated scatter in bias across all volumes. Limits of agreement (defined as mean ± 2 standard deviations [SD]) were large: +189 to -319 mL for FEV1 , equating to large limits of agreement for FEV1 percent predicted of +9.0% to -13.9%. For repeated measurements on the same device on different days, a larger percent SD was obtained with the handheld compared to the conventional spirometer (6.7% vs 5.1%, respectively). Importantly, a relatively large number (15%) demonstrated a decrease in FEV1 percent predicted of ≥10% on the handheld compared to conventional. CONCLUSIONS:This suggests that while both devices have passed the recommendations for spirometry testing per American Thoracic Society/European Respiratory Society, handheld turbine vs conventional spirometers may not be used interchangeably in the pediatric CF population.