A Systematic Review Evaluating Estimated GFR Performance in South Asian Populations

Area of Science:

• Nephrology
• Clinical Chemistry
• Epidemiology

Background:

• Estimated glomerular filtration rate (eGFR) equations are crucial for assessing kidney function.
• Existing eGFR equations demonstrate variable accuracy in diverse populations, particularly in South Asians.

Purpose of the Study:

• To systematically review and meta-analyze the performance of creatinine-based (eGFR_Cr), cystatin-C-based (eGFR_CysC), and combined (eGFR_Cr-CysC) equations against measured GFR (mGFR) in South Asians.
• To identify factors influencing the bias and accuracy of these eGFR equations.

Main Methods:

• A systematic literature search was conducted across major databases (PubMed, Embase, Scopus, Web of Science, Cochrane) for studies published between 1976 and 2024.
• Meta-analyses were performed to evaluate bias (standardized mean difference) and 30% accuracy (P30) of eGFR equations compared to mGFR.
• Multivariable meta-regression was used to explore the impact of moderators like age, sex, ethnicity, and cohort type.

Main Results:

• Thirty-five cohorts (n=4725) were included in the analysis.
• eGFR_Cr equations generally overestimated mGFR, with CKD-EPI-2009_Cr showing the highest bias (SMD=0.66).
• eGFR_CysC equations exhibited the least bias (-0.03 to 0.15), but accuracy (P30) for both eGFR_Cr and eGFR_CysC was below 75%. Combined eGFR_Cr-CysC equations achieved the best P30 (79-82%).

Conclusions:

• Current eGFR equations demonstrate suboptimal accuracy in South Asian populations, consistently failing to meet the 75% P30 clinical benchmark.
• While eGFR_CysC equations reduce bias, combined eGFR_Cr-CysC equations provide superior accuracy.
• Further research on emerging equations like CKD-EPI-Pakistan and EKFC is recommended, with a focus on population-specific calibration in diverse South Asian cohorts.