Cystatin C as a Predictor of In-Hospital Mortality After Exacerbation of COPD.

BACKGROUND: COPD is associated with cardiovascular and renal dysfunction. Cystatin C (CysC) is a biomarker of renal function and an independent risk factor for all-cause and cardiovascular mortality among elderly persons. The aim of the study was to examine the prognostic role of CysC for in-hospital mortality in subjects with a COPD exacerbation. METHODS: Upon admission, serum CysC levels and arterial blood gas analysis from 477 subjects with a COPD exacerbation were measured. Clinical characteristics were also recorded. A receiver operating characteristic curve analysis was used to determine the level of CysC that discriminated survivors from non-survivors. Univariate and multiple logistic regression analyses were used to identify the risk factors for in-hospital mortality. To reduce the influence of confounders, subgroup analyses were performed according to the comorbidities, including states of heart failure, renal dysfunction, and pH, P-aCO2, and P-aO2 levels. RESULTS: During the in-hospital period, 59 subjects died, and 418 subjects recovered. The decedent group showed lower pH (7.27 +/- 0.17 vs 7.38 +/- 0.06, P < .001), higher CysC (2.21 +/- 1.05 mg/L vs 1.39 +/- 0.54 mg/L, P < .001), higher P-aCO2 (77 +/- 39 mm Hg vs 48 +/- 14 mm Hg, P < .001), and lower P-aO2 (74 +/- 32 mm Hg vs 84 +/- 26 mm Hg, P < .001) levels. The area under the receiver operating characteristic curve for the CysC prediction of death was 0.77 (95% CI 0.70-0.84). CysC values >= 1.59 mg/L were associated with significantly higher in hospital mortality (relative risk = 5.49, 95% CI 3.24 -9.32, P < .001). Multiple logistic regression analysis showed that pH < 7.20, CysC >= 1.59 mg/L, and heart failure were independent predictors of in-hospital mortality. The subgroup analysis showed that the comorbid states of renal dysfunction, congestive heart failure, and the levels of pH, P-aCO2, and P-aO2 did not alter the conclusion that CysC was a mortality risk factor for subjects with a COPD exacerbation. CONCLUSION: CysC was a strong and independent risk factor for hospital mortality secondary to COPD exacerbation.