ESPN 51th Annual Meeting

ESPN 2018


 
Concordance of estimated GFR based on creatinine and cystatin C in a broad nephrological population
MARIN MUSTERS 1 EMIL DEN BAKKKER 1 ISABELLE HUBEEK 1 JOANNA VAN WIJK 1 REINOUD GEMKE 1 AREND BOKENKAMP 1

1- VUMC
 
Introduction:

 Recent studies show that high agreement between estimated GFR based on serum creatinine (eGFRcrea) and cystatin C (eGFRcys) indicates high accuracy of the mean of the two estimates.  When the difference between the two (eGFR) is <40%, a P30 accuracy rate of more than 90% has been documented in a research population (den Bakker et al, ClinChimActa 474(2017):38-43). This was the case in ca. 80% of the measurements.

Aim

 To assess the relationship between eGFRcrea, eGFRcys  and eGFR in a broad pediatric nephrological population and identify factors influencing the difference between eGFRcrea and eGFRcys.

Material and methods:

Retrospective analysis on 464 patients from a pediatric nephrology outpatient clinic in whom creatinine and cystatin C were measured simultaneously. The FASage equation was used for creatinine, FAScys for cystatin C. eGFR was calculated as (|eGFRcrea-eGFRcys|)/(0.5x(eGFRcrea+eGFRcys). Concordance between eGFRcrea and eGFRcys was measured using Pearson’s correlation. Diagnosis and steroid use were assessed as potential confounding factors on eGFR using non-parametric tests

Results:

 There was a highly significant correlation of 0.411 between eGFRcrea and eGFRcys (p=0.000). The distribution of eGFR was 0-9%: 27.6%, 10-19%: 28.2%, 20-39%: 33%, >40%: 11.2%. None of the factors studied had a significant influence on ∆eGFR although spina bifida patients trended to have higher eGFR, which was due to high eGFRcreat (median 123.4ml/min/1.73m2 [IQR 42.6] vs 111.4 [30.8], p=0.000).

Conclusions:

 In a broad pediatric nephrological population, eGFR is below 40% in almost 90% of measurements indicating that the average of eGFRcrea and eGFRcys can be used as a reasonable estimate of GFR in the vast majority of patients. In patients with neural tube defects, the cystatin C-based eGFR should be used as shown previously.