Comparing residual kidney function equations based on β2-microglobulin in Chinese patients undergoing continuous ambulatory peritoneal dialysis.

Background: Few studies have evaluated the predictive capability of equations for residual kidney function (RKF) in patients undergoing peritoneal dialysis (PD). Moreover, the applicability of each equation remains unclear. Therefore, we aimed to evaluate the performances of the estimated RKF (eRKF) equations of Shafi, Steubl, and Jaques in Chinese patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

Methods: This was a retrospective study. We enrolled patients who underwent CAPD and RKF measurements (via 24-h urine collection) in our hospital between November 2021 and May 2022. Using the measured RKF (mRKF) as the reference, we derived the bias, precision and accuracy of each equation.

Results: We enrolled 174 participants. The mean β2-microglobulin and median mRKF were 29.00 ± 8.69 mg/L and 2.94 (1.26, 4.65) mL/min/1.73 m, respectively. The Steubl equation had the least bias (MD [95% confidence interval, CI]: -0.52 [-0.77 to -0.38]), higher precision (interquartile range: 1.43 [1.16, 1.76]), and highest accuracy (83%). It also had a high diagnostic accuracy for identifying patients with an mRKF of > 2.5 mL/min/1.73 m, area under the curve of 0.936 95% CI [0.903-0.970],  < 0.001), cut-off value of 1.80 mL/min/1.73 m, specificity of 0.895, and sensitivity of 0.847.

Conclusion: Although no equation was fully accurate, the Steubl equation identified patients suitable for an incremental PD prescription more accurately than the Shafi and Jaques versions. It may be useful for monitoring the RKF of Chinese patients undergoing CAPD who are unable to reliably collect urine.