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Compensating for the influence of total serum protein in the Schwartz formula

Marijn M Speeckaert1, Birgitte Wuyts, Veronique Stove

  • 1Department of Nephrology, Ghent University Hospital, Ghent, Belgium.

Clinical Chemistry and Laboratory Medicine
|September 11, 2012
PubMed

Insights

This study developed a new method to estimate pediatric glomerular filtration rate (GFR) using Jaffe-based creatinine measurements, correcting for serum protein bias. This allows for more accurate GFR estimation in children when enzymatic methods are unavailable.

Area of Science:

  • Pediatric Nephrology
  • Clinical Chemistry
  • Biomarker Measurement

Background:

  • The Schwartz 2009 formula is the standard for pediatric GFR estimation but requires enzymatic creatinine assays.
  • Non-enzymatic Jaffe methods are widely used but can be affected by serum protein levels, leading to inaccurate GFR estimates.
  • A need exists for a reliable GFR estimation method using Jaffe-based creatinine data, especially in resource-limited settings.

Purpose of the Study:

  • To develop and validate a modified Jaffe-based equation for estimating pediatric GFR that accounts for serum protein variations.
  • To assess the performance of the proposed equation against enzymatic creatinine assays and the Schwartz 2009 formula.
  • To enable accurate GFR estimation in children using commonly available Jaffe creatinine methods.

Main Methods:

  • A cohort study involving 100 pediatric patients was conducted.
  • Serum creatinine was measured using Jaffe (compensated) and enzymatic assays.
  • Serum total protein, albumin, urea, uric acid, and total bilirubin were quantified.
  • A novel equation was developed to correct for protein-induced bias in Jaffe creatinine measurements.

Main Results:

  • Serum creatinine differences between enzymatic and compensated Jaffe methods correlated significantly with total protein concentration (r(2)=0.61, p<0.001).
  • The protein-corrected Jaffe method yielded results interchangeable with enzymatic assays (r(2)=0.99, p<0.001).
  • The corrected Jaffe-based GFR estimates were also interchangeable with the Schwartz 2009 formula (r(2)=0.99, p<0.001).

Conclusions:

  • The alkaline picrate (Jaffe) method can be reliably used for GFR estimation in the Schwartz formula by incorporating a serum protein correction.
  • This approach enhances the utility of Jaffe-based creatinine assays for pediatric GFR assessment.
  • Accurate pediatric GFR estimation is achievable with Jaffe methods when accounting for protein bias.
Abstract

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