Difficulties in the interpretation of lung function tests in the diagnosis of asthma and chronic obstructive pulmonary disease.

Objective: To ascertain differences in the interpretation of spirometry and peak flow measurement between primary care (several practioners and nurses) and specialists in patients with a pre-existing diagnosis of asthma and chronic obstructive pulmonary disease (COPD).

Design: A randomized, prospective cohort study of 98 patients with a pre-existing diagnosis of asthma or COPD. Two chest specialists independently interpreted the peak flow and spirometric data and they were also blinded to the primary care results.

Results: There was total agreement in interpretation of the data between general practitioners and specialists in only 20 (20.4%). Levels of diagnostic agreement were highest between the two chest specialists (55%) and lowest between the general practice records and the diagnosis assigned by general practitioners (16%). Disagreement between general practitioners and the two chest specialists was consistent (38%) indicating systematic differences in interpretation.

Conclusions: This study raises concerns about differences in the interpretation of spirometry and peak expiratory flow rates in general and hospital practice and the guidelines on which these interpretations are based.