Accuracy and Quality of Spirometry in Primary Care Offices

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.

We aimed to evaluate spirometer accuracy, determine the clinical significance of inaccurate spirometers, and assess the quality of spirograms obtained in primary care offices.

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.

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.

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.