Background: Spirometry is an indispensable tool for diagnosis and monitoring of chronic airways disease in primary care.
Aim: To establish the quality of routine spirometry tests in general practice, and explore associations between test quality and patient characteristics.
Design of study: Analysis of routine spirometry test records.
Setting: Fifteen general practices which had a working agreement with a local hospital pulmonary function laboratory for spirometry assessment regarding test quality and interpretation.
Method: Spirometry tests were judged by a pulmonary function technician and a chest physician. Proportions of test adequacy were analysed using markers for manoeuvre acceptability and test reproducibility derived from the 1994 American Thoracic Society spirometry guideline. Associations between quality markers and age, sex, and severity of obstruction were examined using logistic regression.
Results: Practices performed a mean of four (standard deviation = 2) spirometry tests per week; 1271 tests from 1091 adult patients were analysed; 96.4% (95% confidence interval [CI] = 95.6 to 97.2) of all tests consisted of ≥3 blows. With 60.6% of tests, forced expiratory time was the marker with the lowest acceptability rate. An overall 38.8% (95% CI = 36.0 to 41.6) of the tests met the acceptability as well as reproducibility criteria. Age, sex, and severity of obstruction were associated with test quality markers.
Conclusion: The quality of routine spirometry tests was better than in previous reports from primary care research settings, but there is still substantial room for improvement. Sufficient duration of forced expiratory time is the quality marker with the highest rate of inadequacy. Primary care professionals should be aware of patient characteristics that may diminish the quality of their spirometry tests. Further research is needed to establish to what extent spirometry tests that are inadequate, according to stringent international expert criteria, result in incorrect clinical interpretations in general practice.