Evaluation of eGFRs to Calculate Kidney Function in Adults with Severe Motor and Intellectual Disabilities

INTRODUCTION: The gold standard for evaluating kidney function is kidney inulin clearance (Cin). However, this procedure is difficult to perform in patients with neuromuscular disabilities and/or bladder dysfunction. We aimed to develop a simpler method for determining the estimated glomerular filtration rate (eGFR) using equations and values for three biomarkers: serum creatinine (sCr), serum cystatin C (cysC), and serum beta-2 microglobulin (β2MG). This study evaluated three eGFR equations in patients with severe motor and intellectual disabilities (SMID). METHODS: We evaluated the equations using data of 18 adult SMID patients with a clinical need for creatinine clearance (Ccr). We compared the results of each equation with Ccr-based eGFR instead of Cin using mean error (ME), root mean square error (RMSE), and P30. RESULTS: Based on eGFR, the ME values of Cr, cysC, β2MG, and Ccr were 74.5, 2.3, and 6.5 mL/min/1.73 m(2), RMSE values, 92.3, 25.7, and 33.4 mL/min/1.73 m(2); and P30, 16.7%, 77.8%, and 72.2%, respectively. CONCLUSIONS: eGFR-Cr cannot be used to reliably assess kidney function in adult SMID patients. It is better to use eGFR-cysC to evaluate kidney function in this patient population.