Applicability of Creatinine- and Cystatin C-Based Estimated Glomerular Filtration Rate Equations in Patients With Neurogenic Lower Urinary Tract Dysfunction.

OBJECTIVES

To assess the applicability of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations and Chinese eGFR Investigation Collaboration (C-eGFR) equations in estimating glomerular filtration rate (GFR) in patients with neurogenic lower urinary tract dysfunction (NLUTD). These equations are based on serum creatinine, cystatin C, or combined creatinine and cystatin C.

METHODS

This prospective study enrolled 142 adult patients with NLUTD. GFR was measured using the dual plasma ⁹⁹mTc-DTPA plasma clearance method. We compared the bias, precision, accuracy and correct classification percentage of six estimated glomerular filtration rate (eGFR) equations, including CKD-EPI creatinine equation (CKD-EPIcr), C-eGFR creatinine equation (C-eGFRcr), CKD-EPI creatinine-cystatin C equation (CKD-EPIcr-cys), C-eGFR creatinine-cystatin C equation (C-eGFRcr-cys), CKD-EPI cystatin C equation (CKD-EPIcys), and C-eGFR cystatin C equation (C-eGFRcys).

RESULTS

The median (interquartile range [IQR]) of measured GFR (mGFR) was 60.54 (34.66-86.28) mL/min/1.73 m². Both CKD-EPIcr and C-eGFRcr significantly overestimated GFR (median differences of 17.20 and 13.60 mL/min/1.73 m², respectively; both p < 0.01), and P30 values (percentage of estimated GFR within 30% of mGFR) were 51% and 57%, respectively. CKD-EPIcr-cys demonstrated superior performance than C-eGFRcr-cys (median difference: 2.07 vs 9.13 mL/min/1.73 m²; both p < 0.01; P30: 84% vs 69%). CKD-EPIcys achieved the highest P30 (88%), while C-eGFRcys showed minimal bias (median difference: 0.42 mL/min/1.73 m²; p = 0.69). CKD-EPIcr-cys, CKD-EPIcys, and C-eGFRcys all achieved acceptable P30 values and correct classification percentage. CKD-EPIcr-cys performed optimally at mGFR ≥ 60 mL/min/1.73 m², whereas CKD-EPIcys was superior at mGFR < 60 mL/min/1.73 m².

CONCLUSION

Creatinine-based equations systematically overestimate GFR in NLUTD patients and should be used with caution. In contrast, cystatin C-based equations-whether used alone (e.g., CKD-EPIcys, C-eGFRcys) or combined with creatinine (e.g., CKD-EPIcr-cys)-demonstrate superior accuracy and should be preferred for GFR estimation in NLUTD patients.

CLINICAL TRIAL REGISTRATION: The Chinese clinical trial registration number is ChiCTR2100054934.