Despite intense research the optimal endogenous biomarker for glomerular filtration rate (GFR) estimation has not been identified yet. We analyzed if ß-trace protein (BTP) improved GFR estimation in elderly. 566 participants aged 70+ from the population-based Berlin Initiative Study were included in a cross-sectional validation study. BTP, standardized creatinine and cystatin C were measured in participants with iohexol clearance measurement as gold standard method for measured GFR (mGFR). In a double logarithmic linear model prediction of mGFR by BTP was assessed. Analyses with BTP only and combined with creatinine and cystatin C were performed. Additionally, performance of GFR estimating equations was compared to mGFR. We found that the combination of all three biomarkers showed the best prediction of mGFR (r2 = 0.83), whereat the combination of creatinine and cystatin C provided only minimally diverging results (r2 = 0.82). Single usage of BTP showed worst prediction (r2 = 0.67) within models with only one biomarker. Subgroup analyses (arterial hypertension, diabetes, body mass index ≤23 and >30) demonstrated a slight additional benefit of including BTP into the prediction model for diabetic, hypertensive and lean patients. Among BTP-containing GFR equations the Inker BTP-based equation showed superior performance. Especially the use of cystatin C renders the addition of BTP unnecessary.

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This Article contains errors in the results of the Full Age Spectrum (FAS) (crea/cys). For the original calculation of mean bias, SD of differences, P10 and P30 value as well as Bland Altman in Figure 3 the rescaling factor for Serum creatinine (Scr) was switched for females and males. As a result, in the Results section, under subheading 'Performance of BTP based estimating equations and comparison with established equations' , "All in all the BIS2 showed the best performance, which is not surprising since it was developed from the BIS dataset, and the FAS was relatively equal to Inker (BTP) and superior to CKD-EPI (Crea/CysC). " should read: "All in all the BIS2 showed the best performance, which is not surprising since it was developed from the BIS dataset, and the FAS (crea/cys) was relatively equal to BIS2 and superior to Inker (BTP) and ECD-EPI (crea/cysc). " In addition, the correct Table 3, showing the correct details for the FAS (Crea/Cys) row, is shown below as Table 1.