How representative are clinical study patients with asthma or COPD for a larger "real life" population of patients with obstructive lung disease?

Evidence-based medicine is a corner stone in treatment decision making and large randomised, clinical trials are usually designed in order-to provide highly significant results. This study was conducted in order to find out to what extend a "real life" patient population with obstructive lung disease could fit into criteria commonly used in clinical research trials. As a secondary aim of the study, eve wanted to compare the OLD population recruited from GP's and specialist outpatient clinics, respectively. Eight-hundred and seventy prospective OLD patients were included. Criteria's for selecting asthma patients to a clinical trial were, absence of co-morbidity, FEV 50-85% of predicted, present or historical reversibility 12% last year, non-smoke or if ex-smoke a smoke burden less then 10 pack years. Only 5.4% of the study asthma patients met with these criteria. Additional criteria's as being symptomatic and regular use of inhaled corticosteroids reduced the numbers of eligible asthma patients to 3.3% representing 1.3% of the entire population. The same procedure was applied for the COPD patients, requesting a FEV1 < 70% of predicted normal, significant smoke history (> 15 pack years) and absence of atopy. This selected 17% of the COPD population, representing 7% of the entire population. We conclude that "evidence based" treatment decisions for OLD are based on studies which include a very small and highly selected fraction of this patient population. It is questionable whether such data can extrapolated to a larger, "real life" population of patients with obstructive lung disease. Moreover, eve found surprisingly minor differences between the Specialist and GP populations. (C) 2004 Elsevier Ltd. All rights reserved.