Association of Differences in Estimated Glomerular Filtration Rate by Cystatin C versus Creatinine with Adverse Events in Adults Undergoing Major Surgery: A Multicenter Cohort Study

INTRODUCTION: The estimated glomerular filtration rate (eGFR) derived from either creatinine (eGFRcr) or cystatin C (eGFRcys) is common preoperative test in routine clinical practice. Recently, the difference between eGFRcys and eGFRcr (eGFRdiff) has been suggested to reflect health status and frailty. This study was aimed to determine the association of eGFRdiff with adverse events among adults undergoing major surgery. METHODS: We conducted a retrospective cohort study of adults undergoing major surgery from 19 academic healthcare centers across China from January 1, 2013, to December 31, 2020. The eGFRdiff was categorized based on previous studied, that is, negative eGFRdiff (<-15 mL/min/1.73 m2), midrange eGFRdiff (-15 to 15 mL/min/1.73 m2), and positive eGFRdiff (≥15 mL/min/1.73 m2). Multivariate logistic regression was performed to assess the association of eGFRdiff with 30-day mortality, 90-day mortality, admission to intensive care unit (ICU), and development of postoperative acute kidney injury (AKI) after surgery. RESULTS: Among 158,336 participants undergoing major surgery, the mean age was 57 years and 52.5% were male. The most frequent surgery type was general (47.5%), followed by the orthopedic (17.0%) and thoracic surgery (12.9%). The mean eGFRdiff was -7.6 mL/min/1.73 m2, negative (<-15 mL/min/1.73 m2) and positive (≥15 mL/min/1.73 m2) eGFRdiff values were observed in 36.1% and 11.6% participants, respectively. In multivariable analyses after adjustment for confounding factors, the negative eGFRdiff had OR of 1.34 (95% CI: 1.20-1.50) for 30-day mortality, 1.33 (95% CI: 1.23, 1.43) for 90-day mortality, 1.46 (95% CI: 1.41-1.50) for admission to ICU, and 1.39 (95% CI: 1.32-1.46) for postoperative AKI. Moreover, the positive eGFRdiff was associated lower risk of 90-days mortality, admission to ICU, and postoperative AKI. CONCLUSIONS: Negative GFRdiff may be a valuable marker for identifying individuals at a higher risk of adverse events in participants undergoing major surgery.