Interpretation of spirometry: Flow-volume curve recognition and decision-making by the general practitioner

Abstract

Background:Spirometry is increasingly implemented in general practice, while the ability of general practitioners (GPs) to interpret flow-volume curves (F-V curves) has been questioned. Studies so far have focused on overall scoring, neither taking into account separate disease patterns encountered in general practice, nor the influence of the F-V curve on the GPs decision-making process.Aim/Method:To determine (1) the achievements of 39 trained GPs as compared with an expert consensus panel in interpreting 12 cases with a wide range of F-V curves and (2) the influence of the F-V curve on the GPs decision-making. Diagnostic test characteristics were calculated by multi-level analysis and expressed in positive and negative predictive values (PPV, NPV) and diagnostic odds ratios (DOR).Results:Normal and obstructive F-V curves were reasonably well diagnosed (PPV 87.0%, NPV 93.3%, DOR 65.0 and PPV 75.1%, NPV 95.7%, DOR 48.9 respectively) while rare and mixed patterns achieved considerably lower scores (PPV 58.3%, NPV 88.4%, DOR 8.5 and PPV 40.8%, NPV 96.1%, DOR 13.1 respectively). Intermediate scores were obtained in the recognition of incorrect manoeuvres (PPV 67.7%, NPV 93.2%, DOR 24.4). The F-V curve influenced the GPs decision-making in reducing the differential diagnosis (OR 2.04 95%CI [1.79, 2.31]), but increased referral rates (OR 7.26 95% CI [4.71, 11.2]) and use of diagnostic prednison courses (OR 4.55 95%CI [3.12, 6.64) considerably.Conclusion:GPs were able to differentiate between normal and obstructive disease patterns, while curves suggestive of rare and mixed pathology were often missed. The F-V curve seems to influence the decision-making process of the GP, but if this represents an initial or general effect remains to be evaluated in practice.