Glomerular Filtration Rate Estimation Using β₂-Microglobulin and β-Trace Protein in Adults With Solid Tumors: A...

β₂-Microglobulin (B2M) and β-trace protein (BTP) are novel endogenous filtration markers that may improve the accuracy of estimated glomerular filtration rate (eGFR) beyond creatinine and cystatin C (eGFR_cr-cys), but they have not been assessed in patients with cancer.

Cross-sectional analysis.

Prospective cohort of 1,200 patients with active solid tumors recruited between April 2015 and September 2017.

CKD-EPI equations without race combining B2M and/or BTP with creatinine with or without cystatin C (2-, 3-, or 4-marker panel eGFR).

Performance of equations compared with eGFR_cr-cys and non-GFR determinants of serum B2M and BTP (S_B2M, and S_BTP, respectively). Measured GFR (mGFR) was determined using the plasma clearance of chromium-51 labeled ethylenediamine tetraacetic acid (⁵¹Cr-EDTA).

Bias was defined as the median of the differences between mGFR and eGFR, and 1-P₃₀ was defined as the percentage of estimates that differed by more than 30% from the mGFR (1-P₃₀). Linear regression was used to assess association of clinical and laboratory variables with S_B2M, and S_BTP after adjustment for mGFR.

Mean age and mGFR were 58.8±13.2 SD years and 78.4±21.7 SD mL/min/1.73m², respectively. Performance of the 3-marker and 4-marker panel equations was better than eGFR_cr-cys (lesser bias and 1-P₃₀). Performance of 2-marker panel equations was as good as eGFR_cr-cys (lesser bias and similar 1-P₃₀). S_B2M and S_BTP were not strongly influenced by cancer site.

Participants may have had better clinical performance status than the general population of patients with solid tumors.

B2M and BTP can improve the accuracy of eGFR and may be useful as confirmatory tests in patients with solid tumors, either by inclusion in a multimarker panel equation with creatinine and cystatin C, or by substituting for cystatin C in combination with creatinine.

The most accurate method to assess estimate kidney function is estimated glomerular filtration rate (eGFR) using creatinine and cystatin C (eGFR_cr-cys). We studied whether using β2-microglobulin (B2M) and/or β-trace protein (BTP) with creatinine with or without cystatin C (2-, 3-, or 4-marker panel eGFR) might be useful in patients with active solid tumors. The performance of the 3-marker and 4-marker panel equations was better than eGFR_cr-cys. Performance of 2-marker panel equations was as good as eGFR_cr-cys. We conclude that B2M and BTP can improve the accuracy of eGFR and may be useful as a confirmatory test in patients with solid tumors either by inclusion in multimarker panel equation with creatinine and cystatin C or by substituting for cystatin C in combination with creatinine.