Validation of the EKFC equation for glomerular filtration rate estimation and comparison with the Asian-modified CKD-EPI equation in Chinese chronic kidney disease patients in an external study

Abstract

Objectives

The aim of this study is to determine whether new European Kidney Function Consortium (EKFC) equation is more applicable than Asian-modified CKD-EPI equation in clinical practice, having a higher accuracy in estimating GFR in our external CKD population.

Methods

We calculated estimated GFR_EKFC and GFR_CKD-EPI independently using the EKFC and Asian-modified CKD-EPI formulas, respectively. The clinical diagnostic performance of the two equations was assessed and compared by median bias, precision, accuracy (P₃₀) and so on, using ^99mTc-DTPA dual plasma sample clearance method as a reference method for GFR measurement (mGFR). The equation that met the following targets was superior: (1) median bias within ± 3 mL/min/1.73 m²; (2) P₃₀ > 75%; and (3) better precision and 95% limits of agreement in Bland–Altman analysis.

Results

Totally, 160 CKD patients were recruited in our external cohort. GFR_EKFC was highly related to mGFR, with a regression equation of GFR_EKFC=mGFR × 0.87 + 5.27. Compared with the Asian-modified CKD-EPI equation, EKFC equation demonstrated a wider median bias (–1.64 vs. 0.84 mL/min/1.73 m², p < 0.01) that was within 3 mL/min/1.73 m² and not clinically meaningful. Furthermore, the precision (12.69 vs. 12.72 mL/min/1.73 m², p = 0.42), 95% limits of agreement in Bland–Altman analysis (42.4 vs. 44.4 mL/min/1.73 m²) and incorrect reclassification index of the two target equations were almost identical. Although, EKFC equation had a slightly better P₃₀ (80.0% vs. 74.4%, p = 0.01).

Conclusions

The overall performance of EKFC equation is acceptable. There is no clinically meaningful difference in the performance of the Asian-modified CKD-EPI and EKFC equations within the limits imposed by the small sample size.

Keywords:

• Chronic kidney disease (CKD)
• glomerular filtration rate (GFR)
• EKFC equation
• Asian-modified CKD-EPI equation

Acknowledgement

This manuscript has been preprinted at the Research Square, Version 1, posted 15 March 2022. https://doi.org/10.21203/rs.3.rs-1437549/v1

Author Contributions

L.Z. and H.-l.L. analyzed the data and wrote the main manuscript. H.-j.L. and J.-M. collected basic characteristics, the serum specimen of study subjects and performed the experimental operation. W.L. conducted the document retrieval and data entry. J.-m.H. and L.-g.W. performed the ^99mTc-diethylenetriaminepentaacetic acid (^99mTc-DTPA) dual plasma sample experiment. P.X. designed the experiments and revised the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets used and/or analyzed during the current study are available from the correspondence author on reasonable request.

Additional information

Funding

This work was partially supported by the Natural Science Foundation of Hebei Province under Grant number H2020206422.