The association of lung function and St. George's respiratory questionnaire with exacerbations in COPD: a systematic literature review and regression analysis

BACKGROUND: This study investigated the relationship between changes in lung function (as measured by forced expiratory volume in one second [FEV(1)]) and the St. George’s Respiratory Questionnaire (SGRQ) and economically significant outcomes of exacerbations and health resource utilization, with an aim to provide insight into whether the effects of COPD treatment on lung function and health status relate to a reduced risk for exacerbations. METHODS: A systematic literature review was conducted in MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials to identify randomized controlled trials of adult COPD patients published in English since 2002 in order to relate mean change in FEV(1) and SGRQ total score to exacerbations and hospitalizations. These predictor/outcome pairs were analyzed using sample-size weighted regression analyses, which estimated a regression slope relating the two treatment effects, as well as a confidence interval and a test of statistical significance. RESULTS: Sixty-seven trials were included in the analysis. Significant relationships were seen between: FEV(1) and any exacerbation (time to first exacerbation or patients with at least one exacerbation, p = 0.001); between FEV(1) and moderate-to-severe exacerbations (time to first exacerbation, patients with at least one exacerbation, or annualized rate, p = 0.045); between SGRQ score and any exacerbation (time to first exacerbation or patients with at least one exacerbation, p = 0.0002) and between SGRQ score and moderate-to-severe exacerbations (time to first exacerbation or patients with at least one exacerbation, p = 0.0279; annualized rate, p = 0.0024). Relationships between FEV(1) or SGRQ score and annualized exacerbation rate for any exacerbation or hospitalized exacerbations were not significant. CONCLUSIONS: The regression analysis demonstrated a significant association between improvements in FEV(1) and SGRQ score and lower risk for COPD exacerbations. Even in cases of non-significant relationships, results were in the expected direction with few exceptions. The results of this analysis offer health care providers and payers a broader picture of the relationship between exacerbations and mean change in FEV(1) as well as SGRQ score, and will help inform clinical and formulary-making decisions while stimulating new research questions for future prospective studies.