Research article

Diagnostic accuracy of spirometry in primary care

Antonius Schneider¹ , Lena Gindner² , Lisa Tilemann² , Tjard Schermer³ , Geert-Jan Dinant⁴ , Franz Joachim Meyer⁵ and Joachim Szecsenyi²

¹  Institute of General Practice, Technische Universität München, München, Germany

²  Department of General Practice and Health Services Research, University Hospital, University of Heidelberg, Heidelberg, Germany

³  Department of Primary Care Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands

⁴  Department of General Practice, School for Public Health and Primary Care, Maastricht University, Maastricht, The Netherlands

⁵  Department of Cardiology, Pulmonology and Angiology, Medical Centre, University of Heidelberg, Heidelberg, Germany

author email corresponding author email

BMC Pulmonary Medicine 2009, 9:31doi:10.1186/1471-2466-9-31

Published:	10 July 2009

Abstract

Background

To evaluate the sensitivity, specificity and predictive values of spirometry for the diagnosis of chronic obstructive pulmonary disease (COPD) and asthma in patients suspected of suffering from an obstructive airway disease (OAD) in primary care.

Methods

Cross sectional diagnostic study of 219 adult patients attending 10 general practices for the first time with complaints suspicious for OAD. All patients underwent spirometry and structured medical histories were documented. All patients received whole-body plethysmography (WBP) in a lung function laboratory. The reference standard was the Tiffeneau ratio (FEV₁/VC) received by the spirometric maneuver during examination with WBP. In the event of inconclusive results, bronchial provocation was performed to determine bronchial hyper-responsiveness (BHR). Asthma was defined as a PC₂₀ fall after inhaling methacholine concentration ≤ 16 mg/ml.

Results

90 (41.1%) patients suffered from asthma, 50 (22.8%) suffered from COPD, 79 (36.1%) had no OAD. The sensitivity for diagnosing airway obstruction in COPD was 92% (95%CI 80–97); specificity was 84% (95%CI 77–89). The positive predictive value (PPV) was 63% (95%CI 51–73); negative predictive value (NPV) was 97% (95%CI 93–99). The sensitivity for diagnosing airway obstruction in asthma was 29% (95%CI 21–39); specificity was 90% (95%CI 81–95). PPV was 77% (95%CI 60–88); NPV was 53% (95%CI 45–61).

Conclusion

COPD can be estimated with high diagnostic accuracy using spirometry. It is also possible to rule in asthma with spirometry. However, asthma can not be ruled out only using spirometry. This diagnostic uncertainty leads to an overestimation of asthma presence. Patients with inconclusive spirometric results should be referred for nitric oxide (NO) – measurement and/or bronchial provocation if possible to guarantee accurate diagnosis.