Concordance between glomerular filtration rate estimates using creatinine-based equations and renal scintigraphy

Abstract

Introduction: chronic kidney disease (CKD) affects approximately 10% of the world’s population, and an accurate estimate of the glomerular filtration rate (GFR) is essential for its diagnosis and treatment. Creatinine-based equations like CKD-EPI, MDRD and Cockcroft-Gault (CG) are used to estimate GFR but have limitations in certain subgroups of patients.

Objective: to compare the accuracy of creatinine-based equations versus direct GFR measurement using renal scans and identify subgroups with greater variability. Methods: a cross-sectional observational study was conducted on 430 patients treated at Hospital San José. The GFR was measured using 99mTc-DTPA scintigraphy and was estimated with CKD-EPI, MDRD and CG. The percentage of estimates within 30% of the reference value (P30) was calculated, along with Lin’s concordance correlation coefficient (rho c), and a Bland-Altman analysis was run

Results: CKD-EPI had the lowest average difference compared to the reference method (4.3 mL/min/1.73m2), followed by MDRD (5. 5 mL/min/1.73 m²) and CG (5.6 mL/min/1.73 m2) . The P30 was 52.1% for CKD-EPI, 49.3% for MDRD and 45. 4% for CG. CKD-EPI had the highest concordance (rho c = 0.544).

Conclusions: CKD-EPI had the highest precision for estimating GFR, especially in patients with almost normal renal function. However, in advanced stages, the equations tended to overestimate GFR, and therefore renal scans continue to be a useful reference method for more accurate GFR measurement.