The usefulness of cystatin C and related formulae in pediatrics

Abstract

Serum creatinine does not share the properties of an ideal marker of glomerular fi ltration rate (GFR) like inulin, but continues to be the most widely used endogenous marker of GFR. In the search of a better biomarker of GFR, the small molecular weight protein cystatin C has been introduced with features more similar to that of inulin, such as constant production and no non-renal elimination. However, it has not enjoyed widespread use despite its signifi cantly improved diagnostic performance in the detection of impaired GFR and its independence of body composition. A variety of formulae based on either cystatin C or creatinine or both have been developed to estimate GFR. We summarize the currently used methods of GFR measurement, their limitations and analytical errors. The review also summarizes the history, features and the feasibility of cystatin C measurements as well as the most widely used formulae for the estimation of GFR in children. The diagnostic performance of the cystatin C derived eGFR formulae at various levels of GFR is also discussed. An eGFR formula derived from pooled studies analyzing both creatinine and cystatin C, and using a biology-based mathematical approach may be advantageous.

Modification of the Schwartz equations for children increases their accuracy at eGFR > 60 mL/min/1.73 m2

“…A separate group consists of children with body deformities and malnutrition, in whom determination of creatinine concentration by itself may be inaccurate and insufficient. 36 As other authors, we suggest an additional cystatin C determination in this group. It should be remembered that multi-marker equations take into account the height of the patient, what in case of children with body disproportions may affect the error of the result in an identical manner as in case of uni-marker equations.…”

“…The findings of this study unambiguously indicate (Tables 15-18 and 23 and Figures 1 and 2, 9-field tables) that multi-marker equations are more accurate than unimarker formulas, which confirms others opinions. 24,36,38 The greatest advantage of this study is the assessment of the real GFR based on iohexol method in a large group of children with normal kidney function and the own proposal of modifying the Schwartz equations. This seems to be a more practical solution than introducing new forms of the equations.…”

Reference ranges for serum β-trace protein in neonates and children younger than 1 year of age

“…First, GFR was not evaluated with a gold standard (such as inulin clearance) [4,6]. This invasive and time-consuming method would not have been approved by the Ethics Board, as in the Netherlands non-therapeutic studies in minors are only allowed by law when risks and burdens are minimal.…”

“…The exogenous marker inulin is widely considered the gold standard in this respect, although its measurement is cumbersome and invasive and therefore not suitable for regular monitoring of kidney function in the clinical setting [4]. An alternative is the use of endogenous markers, of which serum creatinine (SCr) is the most commonly used [4][5][6].…”

Staging chronic kidney disease and estimating glomerular filtration rate: an opinion paper about the new international recommendations

“…Several review articles have been published on the topic, including in this journal [53][54][55]. One of the main limitation of cystatin C and cystatin C-based equations was the lack of standardization between assays leading to potential discrepancies similar to the ones observed in creatinine-based equations [56][57][58][59].…”