Spirometrisch onderzoek bij patiënten met chronisch obstructief longlijden in de huisartspraktijk en in een longfunctielaboratorium even betrouwbaar, maar niet onderling uitwisselbaar

Objective. To investigate the reliability of Spirometric tests performed in general practice. 

Design. Comparison of two diagnostic tests. 

Method. A repeated within-subject comparison of Spirometric tests was performed on 388 subjects with chronic obstructive pulmonary disease (COPD) from 61 general practices and 4 laboratories. The standard was a test performed in a pulmonary function laboratory. General practitioners and practice assistants undertook a spirometry training programme at the start of the study. Within-subject differences in forced expiratory volume in I second and forced vital capacity (ΔFEV₁ and ΔFVC) between laboratory and general practice tests were measured as primary outcomes (practice minus laboratory value). The tests were repeated after one year. The proportion of tests with an FEV ₁ difference < 5% and < 200 ml served as a quality marker. 

Results. Mean ΔFEV₁ was 0.069 1 (95% CI: 0.054-0.084) and ΔFVC 0.081 1 (95% CI: 0.053-0.109) in the first-year evaluation, indicating consistently higher values for general practice measurements. Second-year results were similar. Laboratory and general practice FEV ₁ values differed by up to 0.5 1, FVC values by up to 1.0 1. The proportion of non-reproducible tests was 16% for laboratory tests and 18% for general practice tests (p = 0.302) in the first-year evaluation, and 18% for both in the second-year evaluation (p = 1.000). 

Conclusion. Relevant Spirometric indices measured by trained general-practice staff were marginally (but statistically significantly) higher than those measured in pulmonary-function laboratories. Because of the limited agreement between laboratory and general-practice values, the interchangeable use of measurements from these two different locations is best avoided. As long as the practice staff receives sufficient training, the current practice of performing Spirometric tests in the primary-care setting seems to be justifiable on the basis of this study.