The effect of serum creatinine method choice on estimated glomerular filtration rate determined by the abbreviated...

Area of Science:

• Clinical Chemistry
• Renal Function Assessment

Background:

• Variability in estimated glomerular filtration rate (eGFR) calculations exists due to differing creatinine assays.
• Laboratories in Northern Ireland utilize various creatinine assays beyond the Beckman CX3, impacting eGFR accuracy.

Purpose of the Study:

• To quantify the variability in eGFR estimations across different creatinine assays used in Northern Ireland.
• To assess the impact of method-specific biases on eGFR calculations.

Main Methods:

• Serum creatinine levels were measured in 50 patient samples using kinetic Jaffe assays on Roche modular P-800, Beckman LX20, and Abbott Aeroset analyzers.
• Estimated glomerular filtration rate (eGFR) was calculated using the abbreviated Modification of Diet in Renal Disease (MDRD) equation.

Main Results:

• Median eGFR values varied between assays: Beckman (45.4 mL/min/1.73 m2), Roche (49.2 mL/min/1.73 m2), and Abbott (50.0 mL/min/1.73 m2).
• After mathematical alignment to the Beckman method, Roche and Abbott assays showed adjusted median eGFRs of 44.0 and 45.6 mL/min/1.73 m2, respectively.
• Method-related biases in eGFR were found to be minimal (up to 10%) relative to the overall variance.

Conclusions:

• Regression equations derived from this study enable alignment of creatinine assay methods.
• While method biases exist, they are considered minimal within the broader context of eGFR variance observed in the 90% confidence intervals.