Current clinical guideline definitions for airflow obstruction leads to substantial overdiagnosis of COPD in primary care

¹ Dept of General Practice, Radboud University Nijmegen Medical Centre (117/HAG), PO Box 9101, 6500 HB Nijmegen, the Netherlands
² Stichting Huisartsen Laboratorium Etten-Leur/Breda (SHL), PO Box 228, 4870 AE Etten-Leur, the Netherlands
³ Stichting Huisartsen Laboratorium Oost (SHO), PO Box 261, 6880 AG Velp, the Netherlands
⁴ Diagnostisch Centrum Eindhoven (DCE), PO Box 6274, 5600 HG Eindhoven, the Netherlands
⁵ Dept of Lung Diseases, Franciscus Hospital, Boerhaavelaan 25, 4708 AE Roosendaal, the Netherlands
⁶ Dept of Lung Diseases, Radboud University Nijmegen Medical Centre, (454/long), PO Box 9101, 6500 HB Nijmegen, the Netherlands

	Abstract

Establish agreement between two recommended definitions for airflow obstruction in symptomatic adults referred for spirometry by their general practitioner, and investigate how rates of airflow obstruction change when prebronchodilator in stead of postbronchodilator spirometry is used.

We analysed diagnostic spirometry tests of 14,056 adults with respiratory. We looked at differences in interpretation between a fixed 0.70 FEV1/FVC cut-point and a sex and age specific lower limit of normal (LLN) cut-point for this ratio.

53% of all subjects were females, 69% were (ex)smokers. Mean postbronchodilator FEV1/FVC was 0.73 (SD 0.13) for males and 0.78 (SD 0.11) for females. Sensitivity of the fixed cut-point relative to the LLN cut-point definition was 97.9%, specificity 91.2%, positive predictive value 72.0%, and negative predictive value 99.5%. For a subgroup of 50+ (ex-)smokers: 100%; 82.0%; 69.2%, and 100%. Proportions of false positive diagnoses when using the fixed cut-point increased with age (2 test: p<0.001). Positive predictive value of prebronchodilator airflow obstruction was 74.7% among 50+ (ex-)smokers.

The current clinical guideline-recommended 0.70 fixed FEV1/FVC cut-off leads to substantial overdiagnosis of obstruction in middle-aged and elderly patients in primary care. Using prebronchodilator spirometry leads to a high rate of false positive interpretations for obstruction in primary care.

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