Diagnostic differentiation between asthma and COPD in primary care. The added value of spirometry

Clinical Research Results Abstract IntroductionAsthma and COPD are common chronic obstructive lung diseases. The two conditions are defined as different disease entities, but in clinical practice patients often show features of both diseases. These similarities make it challenging for clinicians to establish a correct diagnosis, especially in primary care settings. Aim of this study was to (i) establish patient characteristics that distinguish between asthma and COPD and (ii) establish the added value of spirometry and more advanced lung function measurements to differentiate between these two chronic airways diseases MethodsThe study was a cross-sectional, non-interventional, multicentre study in 10 general practices in The Netherlands. 532 subjects were extensively screened on respiratory symptoms and lung function. Two experienced chest physicians assessed if asthma or COPD was present using a clinical guideline-based protocol. Using multivariable logistic regression analysis we identified clinical discriminants of asthma and COPD and assessed the ability of three scenarios (i.e. only patient history; diagnostics available to primary care; diagnostics available only to secondary care) to differentiate between the two conditions. Receiver operator characteristics (ROC) curves and area under the curve (AUC) were calculated for each scenario, with the two chest physicians’ joint assessment serving as the golden standard.ResultsEighty-four (84) subjects were diagnosed with asthma, 138 with COPD, and 310 with no chronic respiratory disease. In the scenario including only patient history items, ROC characteristics of the model showed an AUC of 0.84 (95% confidence interval (CI): 0.78-0.89) for differentiation between asthma and COPD. Important predictors were smoking, presence of wheeze or breathlessness, and presence of allergies. By adding diagnostics available to primary care (i.e., pre- and postbronchodilator spirometry), AUC significantly increased to 0.89 (95%CI 0.84-0.93). When adding more advanced diagnostic tests available only to secondary care (i.e., static lung volumes and capacities, diffusion capacity, bronchial hyperresponsiveness) AUC remained 0.89 (95%CI 0.85-0.94).DiscussionPrimary care clinicians’ ability to differentiate between asthma and COPD using relevant patient history questions can be further enhanced by spirometry testing in patients with underlying chronic obstructive lung disease. More advanced diagnostic tests used in hospital care settings do not provide a better overall diagnostic differentiation between asthma and COPD in primary care patients. Research Idea Abstract Service Development & Evaluation Abstract Declaration of Interest The original DIMCA study was funded by the Netherlands Lung Foundation, combined with an unrestricted research grant by GlaxoSmithKline. The current analysis was funded by Radboud University Medical Center, Nijmegen, The Netherlands. References and Clinical Trial Registry Information