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.