Accuracy and Quality of Spirometry in Primary Care Offices

Rationale: Spirometry is necessary for the optimal management of patients with respiratory disease. The quality of spirometry performed in the primary care setting has been inconsistent. Objectives: We aimed to evaluate spirometer accuracy, determine the clinical significance of inaccurate spirometers, and assess the quality of spirograms obtained in primary care offices. Methods: We tested 17 spirometers used in primary care offices with a waveform generator; accuracy and precision were assessed using American Thoracic Society criteria. The clinical significance of inaccurate instruments was determined by applying the FEV1/FVC error from an obstructed waveform to a clinical data set. Spirogram quality was determined by grading spirograms using acceptability and repeatability criteria. The relationship between the number of tests performed by a clinic and test quality was assessed. Measurements and Main Results: Only 1 of 17 spirometers met accuracy criteria, with mean errors for FVC, FEV1, and FEV1/FVC ranging from 1.7 to 3.1%. Applying the percentage error to a clinical data set resulted in 28% of tests being recategorized from obstructed to nonobstructed. Of the spirograms reviewed, 60% were considered acceptable for clinical use. There was no association between the number of tests performed by a clinic and spirometry quality. Conclusions: Most spirometers tested were not accurate. The magnitude of the errors resulted in significant changes in the categorization of patients with obstruction. Acceptable-quality tests were produced for only 60% of patients. Our results raise concerns regarding the utility of spirometry obtained in primary care offices without greater attention to quality assurance and training.