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Estimation of glomerular filtration rate (GFR) in acute kidney injury (AKI) is problematic as plasma creatinine changes rapidly. There is no widely accepted method for estimating renal function in the setting of AKI. Kinetic estimated GFR formula and creatinine clearance is an estimate of immediate biomarker clearance derived from two discrete measurements that may better represent acute function. However, neither the kinetic GFR formula nor the four-hour creatinine clearance have been evaluated in the Mexican population.
Prospective evaluation of renal function in patients with acute kidney injury by comparison of kinetic estimated GFR formula, four-hour creatinine clearance and cystatin C 2021 CKD EPI formula.
Data were analyzed for 68 patients with a mean age of 67.21 years, 61% were male, and 47% of patients had chronic kidney disease. The mean baseline creatinine was 1.4 mg/dl and the mean GFR was 65.85 mg/dl. The main aetiological factor for AKI was sepsis (33%), followed by cardiorenal syndrome. A Pearson correlation of 0.80 (p= 3.19e-16 CI 95 0.70-0.87) was found between the kinetic estimated GFR formula and four-hour creatinine clearance; concordance was analyzed by the Bland-Altman method with a mean difference of -0.14 with upper LoA of 21.10 (CI 95 16.4-25.7) and lower LoA -21.40 (CI 95 -26.0 -16.7). The concordance between CKD-EPI 2021 and the kinetic estimated GFR formula was 0.84 (CI 95 0.73-0.89). However, the concordance for the kinetic estimated GFR formula and 2021 CKD-EPI cystatin formula was 0.33.
In Mexican patients with AKI, there is no standardization for the calculation of GFR. However, with creatinine determinations, GFR can be estimated using the kinetic estimated GFR formula, although it can also be evaluated by 4-hour creatinine clearance, which showed statistical concordance. Evaluation of GFR in AKI with cystatin did not show a good correlation with either the kinetic estimated GFR formula or 4-hour creatinine clearance.