# Evaluation of Six eGFR Equations in Predicting Acute Kidney Injury in Patients after Off-Pump Coronary Artery Bypass Grafting: A Case Control Study

## TL;DR

This study compares six equations for estimating kidney function to see which best predicts kidney injury after heart surgery.

## Contribution

The study identifies that equations using cystatin C (FAScys and CKD-EPIcys) outperform others in predicting acute kidney injury after heart surgery.

## Key findings

- 319 out of 1428 patients developed acute kidney injury after surgery.
- FAScys and CKD-EPIcys equations showed the best predictive performance with AUCs of 0.744 and 0.739 respectively.
- All eGFR equations were significantly associated with AKI occurrence.

## Abstract

There are six widely used equations to calculate the
estimated glomerular filtration rate (eGFR) of patients. We aimed to assess the
predictive power of preoperative eGFR calculated by these equations for the
occurrence of postoperative acute kidney injury (AKI).

Patients
who underwent isolated coronary surgery from January 2016 to January 2021 were
continuously enrolled. Serum creatinine and cystatin C used to calculate eGFR
were both measured within 1 week before surgery. The eGFR was calculated using
six equations: Cockcroft Gault (CG) equation, Chinese abbreviated modification of
diet in renal disease (MDRD) equation, chronic kidney disease-epidemiology
(CKD-EPI) equation, and full age spectrum (FAS) equation. Postoperative AKI was
diagnosed by Kidney Disease Improving Global Outcomes criteria (KDIGO)
(① urine volume <0.5 mL/kg/h for 6 h; ② an increase in serum
creatinine by ≥26.5 µmol/L within 48 h; ③ an increase in
serum creatinine to ≥1.5 times baseline levels, which is known or presumed
to have occurred within the prior 7 days), and the occurrence of AKI within 7
days after surgery was followed.

A total of 1428 patients were
included, of which 319 patients (25.5%) developed postoperative AKI. After
adjustment, all eGFRs (CG OR = 0.983, MDRD OR = 0.983, CKD-EPIcrea OR =
0.97, CKD-EPIcys OR = 0.955, FAScrea OR = 0.978, FAScys OR = 0.
941, all p
< 0.001) were significantly associated with AKI. The area
under the receiver operating characteristic curve (AUC) was 0.621 for CG, 0.614
for MDRD, 0.643 for CKD-EPIcrea, 0.739 for CKD-EPIcys, 0.643 for
FAScrea, 0.744 for FAScys, respectively. There was no difference in
predictive power between FAScys and CKD-EPIcys (p = 0.33,
DeLong’s test).

Preoperative eGFR calculated by FAScys and CKD-EPIcys equations have better performance in predicting AKI after
off-pump coronary artery bypass grafting than other equations.