Validation of the adult asthma epidemiological score: a secondary analysis of the EPI-ASTHMA population-based study

Abstract

ObjectiveThe A2 score is an eight-question patient-reported outcome measure that has been validated for ruling in (score ≥4) and ruling out (score 0–1) asthma. However, this screening tool has been validated in a cohort similar to the derivation cohort used. This study aims to validate the predictive accuracy of the A2 score in a primary care population against general practitioner (GP) clinical assessment and to determine whether the proposed cut-offs are the most appropriate.DesignThis accuracy study is a secondary analysis of the EPI-ASTHMA population-based study.SettingPrimary care centres in Portugal.ParticipantsRandom adult participants answered the A2 score by phone interview.OutcomesThose with an A2 score ≥1 (plus 5% with an A2 score of 0) were invited to a diagnostic visit carried out by a GP to confirm or not a diagnosis of asthma. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) curves.ResultsA total of 1283 participants (median 54 (p25–p75 43–66) years; 60% women) were analysed. The A2 score showed high discriminatory power in identifying asthma, with an area under the ROC curve of 82.9% (95% CI 80.4% to 85.4%). The proposed cut-off ≥4 was the most appropriate to rule in asthma (specificity 83.1%, positive predictive value 62.4%, accuracy 78%). Similarly, the proposed cut-off<2 was the most suitable for excluding asthma (sensitivity 92.7%, negative predictive value 93.7%, accuracy 60.5%).ConclusionsThe A2 score is a useful tool to identify patients with asthma in a primary care population.Trial registration numberNCT0516961.