The need for robust validation for MDRD-based glomerular filtration rate estimation in various CKD populations

Area of Science:

• Nephrology
• Biostatistics
• Clinical Chemistry

Background:

• Estimated glomerular filtration rate (eGFR) equations are crucial for assessing kidney function but have primarily been validated in Caucasian and African-American populations.
• Previous studies indicate that existing eGFR equations may not be accurate for Asian populations, highlighting the need for race/ethnicity-specific validation.
• The Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations are widely used but require prospective validation in diverse groups.

Purpose of the Study:

• To evaluate the accuracy of existing eGFR equations (MDRD, CKD-EPI, Chinese, and Japanese) in a Thai population with chronic kidney disease (CKD).
• To determine the applicability of current eGFR estimation formulas in a non-Caucasian, non-African-American demographic.
• To develop and propose a new eGFR equation tailored for the Thai population based on study findings.

Main Methods:

• A cohort of 350 adult Thai CKD patients was studied.
• Glomerular filtration rate (GFR) was measured using (99m)Tc-DTPA plasma clearance as the reference standard.
• Serum creatinine levels were measured using both IDMS-traceable enzymatic methods (Cr(Enz)) and Jaffe's kinetic assay (Cr(Jaffe)) according to the requirements of each eGFR equation.

Main Results:

• Significant discrepancies were observed between the reference GFR and eGFR values calculated using existing equations, with the Japanese equation showing the largest disagreement (20.9 mL/min/1.73 m²).
• The reexpressed MDRD equation yielded a disagreement of 9.6 mL/min/1.73 m², and the CKD-EPI equation showed 8.0 mL/min/1.73 m².
• A new Thai-specific MDRD equation was derived using a Thai coefficient (1.129), and a novel Thai eGFR formula was developed through stepwise multiple regression analysis.

Conclusions:

• Race and ethnicity significantly influence the accuracy of MDRD-based eGFR calculations, underscoring the limitations of applying non-validated equations.
• It is imperative to validate eGFR equations within specific populations before their clinical or epidemiological application to ensure accurate kidney function assessment.
• The findings support the development and use of population-specific eGFR equations, such as the newly proposed Thai formula, for improved clinical utility in Thailand.