#2948 β-2-MICROGLOBULIN AND β-TRACE-PROTEIN DO NOT IMPROVE ESTIMATION OF GFR IN KIDNEY TRANSPLANT RECIPIENTS COMPARED TO CREATININE AND CYSTATIN C Free

Precise estimates of glomerular filtration rate (eGFR) are important in kidney transplant recipients (KTRs). Current eGFR formulas based on plasma creatinine and/or cystatin C are associated with significant bias. We investigated whether race free formulas based on plasma values of β-trace-protein and β-2-microglobulin performed better than formulas based on creatinine and cystatin C in a Scandinavian cohort of KTRs.

We included samples and data from the randomised, controlled trial CONTEXT. GFR was measured by plasma clearance of ⁵¹Cr-EDTA or iodothalamate. eGFR was calculated using the new race-free CKD-EPI eGFR-creatinine and/or cystatin C(2021) formulas as well as the CKD-EPI eGFR-β-trace-protein and/or eGFR-β-2-microglobulin formulas. GFR estimates were evaluated at 3 (n = 82) and 12 (n = 64) months post-transplant using mean bias, precision, and accuracy. Also, formulas were analysed for their ability to correctly classify changes in measured GFR from 3 to 12 months.

At 12 months eGFR-creatinine-cystatin C performed best according to mean bias (−4.54 ml/min/1.73 m²), precision (SD = 8.18 ml/min/1.73 m²) and accuracy (P10 = 47%) among creatinine and cystatin C based formulas (Table 1). Among the β-trace-protein and β-2-microglobulin based formulas, eGFR-β-trace-protein-β-2-microglobulin performed best according to precision (SD = 7.64 ml/min/1.73 m²) and accuracy (P10 = 36%) (Table 1). eGFR-β-trace-protein-β-2-microglobulin and eGFR-creatinine-cystatin C performed similar when comparing residuals (p = 0.481). eGFR-β-trace-protein, eGFR-β-trace-protein-β-2-microglobulin and eGFR-creatinine-cystatin C performed best in correctly classifying changes in mGFR from 3 to 12 months.

β-trace-protein and β-2-microglobulin do not improve the measurement of GFR compared to creatinine and cystatin C based formulas in KTRs.