RESUMEN
Introduction: The use of two quality-of-life questionnaires in a single clinical trial with an economic component can be challenging due to the associated workload in terms of data collection and an increased risk of missing data. The aim of our study was to determine whether the questionnaire chosen to measure health status, the St. George's Respiratory Questionnaire (SGRQ), could be administered on its own without adding the EuroQol five dimensions questionnaire (EQ-5D) for economic evaluation in emphysema studies. Materials and Methods: Data were prospectively collected during the REVOLENS trial assessing endobronchial coil treatment in severe emphysema. To quantify the association between the two questionnaires, correlations between the EQ-5D and the SGRQ were first tested and the concordance was then studied in order to know whether the two questionnaires were interchangeable. Finally, the Starkie et al algorithm predicting EQ-5D utility values from the SGRQ was used on REVOLENS's individual patient data. The Student's t-test, correlation and concordance between EQ-5D individual value (from the REVOLENS study) and predicted value (from the Starkie et al algorithm) were studied to test this algorithm. Results: Results showed a strong correlation but no concordance between the EQ-5D and the SGRQ, demonstrating that the two questionnaires are not interchangeable. Moreover, the algorithm predicting EQ-5D utilities from the SGRQ did not provide utility values comparable to those observed in the REVOLENS study. Indeed, our study demonstrated a strong correlation between predicted and individual EQ-5D values but no concordance. Conclusion: The use of both the EQ-5D and the SGRQ in a clinical study with an economic component is justified. Based on our results, the SGRQ should not be used to obtain a utility score to calculate the incremental cost-effectiveness ratio and conclude on the efficiency of an intervention in emphysema patients.