Kidney Function Surveillance in the National Spina Bifida Patient Registry: A Retrospective Cohort Study

Abstract

Purpose: Chronic kidney disease affects 25% to 50% of patients with spina bifida. Guidelines recommend kidney function surveillance in these patients but practice patterns are unknown. Variations in kidney function surveillance were assessed in patients with spina bifida based on the hypothesis that the treating clinic and spina bifida type would be associated with kidney function surveillance.

Materials and methods: A retrospective cohort study was conducted of U.S. patients in the National Spina Bifida Patient Registry from 2013 to 2018. Followup was anchored at the 2013 visit. Participants with either an outcome event within 2 years of followup or more than 2 years of followup without an outcome event were included. Primary outcome was kidney function surveillance, defined as at least 1 renal ultrasound and serum creatinine within 2 years of followup. Primary exposures were clinic and spina bifida type, which were analyzed with covariates including sociodemographic and clinical characteristics in logistic regression models for their association with the outcome. Sensitivity analyses were performed using different kidney function surveillance definitions.

Results: Of 8,351 patients 5,445 were included with a median followup of 3.0 years. Across 23 treating clinics kidney function surveillance rates averaged 62% (range 6% to 100%). In multivariable models kidney function surveillance was associated with treating clinic, younger patient age, functional lesion level, nonambulatory status and prior bladder augmentation. Treating clinic remained a significant predictor of kidney function surveillance in all sensitivity analyses.

Conclusions: Within the National Spina Bifida Patient Registry wide variation exists in practice of kidney function surveillance across treating clinics despite adjustment for key patient characteristics.

Keywords: chronic; kidney function tests; neurogenic; renal insufficiency; spina bifida cystica; spinal dysraphism; urinary bladder.

Figure 1.

Participant Selection Flowchart, National Spina Bifida Patient Registry, 2013–18.

Figure 2.

Kidney Function Surveillance rates varied significantly across Treating Clinics (n=23 clinics, 5445 patients; p<0.001), National Spina Bifida Patient Registry, 2013–18.

Figure 3.

Kidney Function Surveillance rates in sensitivity analyses. (a) Kidney Function Surveillance rates using 1-year window; (b) Kidney Function Surveillance rates using ultrasound-only in 2-year window; (c) Kidney Function Surveillance rates using serum creatinine-only in 2-year window. All rates varied significantly across Treating Clinics (p<0.001), National Spina Bifida Patient Registry, 2013–18.