### Abstract

Purpose: Estimated glomerular filtration rate (eGFR) in the general population is stable in children after 2 years of age until adulthood. In the first three decades after age 18, eGFR decreases by 0.3–0.8 ml/min/1.73 m^{2}/year. Little data exists regarding eGFR changes in the spina bifida (SB) population given variability in muscle mass. In the absence of a validated SB-specific eGFR formula, the performance of different eGFR formulas may vary. We performed a cross-sectional study (1) to determine trends in eGFR with increasing age in children and adults with SB and (2) to compare eGFRs calculated using different formulas. Methods: We retrospectively reviewed records of patients 2–50 years old with SB followed at our institution (2014–2019). We determined eGFR using four pediatric formulas (2–17 years: CKiD_{SCr}, CKiD_{Cys}, CKiD_{SCr-Cys}, Zappitelli_{SCr-Cys}) and four adult formulas (18 + years: MDRD_{SCr}, CKD-EPI_{SCr}, CKD-EPI_{Cys}, CKD-EPI_{SCr-Cys}). One eGFR per patient was included (most recent eGFR for those with serial measurements). Patients were categorized as chronic kidney disease (CKD) stage 2 (eGFR 60-89) and Stage 3+ (<60). Non-parametric tests, linear regression, and Spearman's correlation were used for analysis. Results: Among 209 children with SB (median age 10.3 years), depending on the formula used, eGFR decreased by −0.7 to −1.8 ml/min/1.73 m^{2}/year (CKiD_{Cys}, CKiD_{Scr}, p ≤ 0.001), remained stable (CKiD_{SCr-Cys}, p = 0.41), or increased by +2.7/year (Zappitelli_{SCr-Cys}, p < 0.001) (Figure). The proportion of children with CKD 2 or higher varied between formulas (11.5–58.9%, p < 0.001). Correlations between pediatric formulas were negligible to moderate. Comparing any two formulas, 12.0–65.6% of children were assigned a different CKD stage. Among 164 adults (median age 26.3), eGFR decreased for each formula (range: −1.3 to −2.2/year, p ≤ 0.01) (Figure). The proportion of adults with CKD 2 or higher varied between formulas (9.2–30.5%, p < 0.001). Correlations between adult formulas were moderate to very high. Comparing any two formulas, 8.5–26.8% of adults were assigned a different CKD stage. Comment: We cannot reliably determine whether eGFR changed during childhood. Among adults, eGFR decreased with age for every formula evaluated at greater than twice the general population rate. Without a validated SB-specific eGFR formula, we are left with formulas providing different results. Conclusions: Estimated GFR among adults with SB appears to deteriorate at a higher rate than in the general population. Due to lack of precision of accepted eGFR formulas in the SB population, this may be a real phenomenon, an artifact of inaccurate eGFR formulas, or both. A validated SB-specific eGFR formula is needed.[Formula presented]

Original language | English (US) |
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Journal | Journal of Pediatric Urology |

DOIs | |

State | Accepted/In press - Jan 1 2020 |

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### Keywords

- Chronic
- Creatinine
- Cystatin C
- Renal insufficiency
- Spinal dysraphism

### ASJC Scopus subject areas

- Pediatrics, Perinatology, and Child Health
- Urology

### Cite this

*Journal of Pediatric Urology*. https://doi.org/10.1016/j.jpurol.2019.12.009