Discordances between Preoperative Creatinine- and Cystatin C–based Estimated Glomerular Filtration Rate and Outcomes after Noncardiac Surgery: An Observational Study

BACKGROUND: Differences between cystatin C- and creatinine-based estimated glomerular filtration rate (eGFR) have been associated with adverse outcomes in both chronic disease and general population cohorts, but their significance in surgical patients is unknown. The hypothesis of this study was that lower cystatin C-based relative to creatinine-based eGFR would be associated with higher risks of postoperative complications. METHODS: This was a retrospective cohort study of patients who had major noncardiac surgery at two large hospitals in China, located in geographically distant regions and with differing ethnic compositions. The exposure was different in preoperative eGFR based on cystatin C and creatinine (eGFRdiff = eGFRcys - eGFRcr). The primary outcome was a composite of postoperative complications and death. Associations were assessed using logistic regression models adjusting for demographics, comorbidities, surgery characteristics, and laboratory results. RESULTS: A total of 35,488 patients from the Nanfang cohort and 23,417 from the Xinjiang cohort were included. The primary outcome occurred in 8.4 and 14.4% of patients, respectively. More negative eGFRdiff values were consistently associated with higher risk of the primary outcome (adjusted odds ratio per 10 ml · min -1 · 1.73 m -2 decrease was 1.12 [95% confidence interval, 1.09 to 1.15] in the Nanfang cohort and 1.11 [95% confidence interval, 1.09 to 1.14] in the Xinjiang cohort; both P < 0.001). Associations were also observed across categories of component outcomes (cardiovascular events, acute kidney injury, infections, pulmonary complications, and death). CONCLUSIONS: More negative preoperative eGFRdiff was independently associated with higher risk of postoperative complications in Asian patients undergoing noncardiac surgery. eGFRdiff may represent a novel risk marker with potential utility for perioperative risk stratification.