Glomerular filtration rate: measure creatinine and height rather than cystatin C!

Abstract

Aim. Inulin clearance (Cin) is the gold standard for assessing glomerular filtration rate (GFR). Other methods are based on the plasma creatinine concentration (Pcreat), creatinine clearance (Ccreat), the Haycock‐Schwartz formula and the plasma concentration of cystatin C (PcysC), a 13kDa basic protein produced at a constant rate by all nucleated cells. The present prospective study was thus designed to evaluate the reliability of PcysC as a marker of GFR in comparison with that of Pcreat, Ccreat and the Haycock‐Schwartz formula, using Cin as the gold standard. Methods: Ninety‐nine children (51 m/48 f), with a median age of 8.3 y (1.0–17.9) were studied. Using a cut‐off for Cin of 100ml/min per 1.73 m2, 54 children (54.5%) had impaired GFR. Those with normal GFR were comparable for age, height, weight and body mass index. Results: Logistic regression, ROC analysis and linear regression all showed that Ccreat was the best parameter to discriminate between impaired and normal GFR, followed by the Haycock‐Schwartz formula, PcysC, and finally Pcreat, each one being significantly more predictive than the next. Conclusion: GFR is better assessed by the Haycock‐Schwartz formula than by PcysC or Pcreat alone. It is therefore concluded that when urine collection is not possible, simply measuring the child's Pcreat and height is the best, easiest and cheapest way to assess GFR.

Cystatin C: current position and future prospects

“…Some believe that agerelated reference values should be reported, which makes analysis of the sensitivity and specificity of new markers difficult (139). The lack of simple data on normal GFR values in paediatric practice explains why the values considered to be ''normal'' for GFR in receiver operator characteristic (ROC) curve analyses vary depending on the author from 60 to 100 mL/min/ 1.73 m 2 (124,140). The fact that CysC does not depend much, if at all, on muscle mass is an important theoretical advantage over creatinine in paediatric practice (50,51).…”

Glomerular filtration rate measurement and estimation in chronic kidney disease

“…Other studies have shown that plasma cystatin C is slightly better than plasma creatinine in diagnosing renal insufficiency but is less sensitive than creatinine clearance or eGFR (from k×L/Pcr) [48]. Moreover, cystatin C levels may underestimate GFR in renal transplant patients [49].…”

Population pharmacokinetics and pharmacodynamics of teicoplanin in neonates: making better use of C-reactive protein to deliver individualized therapy

“…The effect of weight, PMA, postnatal age, serum creatinine and estimated glomerular filtration rate (eGFR) using the Haycock-Schwartz formula (K×height/serum creatinine 15 ; the UK population median height values for age and sex were used for each patient; and K ¼ 0.33 for preterm neonates and K ¼ 0.45 for term neonates) on the population PK of teicoplanin was explored. 16,17 The Bayesian estimates for clearance and volume of distribution from each patient were obtained from the standard model (above) and plotted against weight, PMA, postnatal age, serum creatinine and GFR, using both linear and logarithmic scales.…”