Routine serum creatinine measurements: how well do we perform?

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Nephrology

Background:

• Investigated accuracy and intra-laboratory variation of serum creatinine measurements in clinical labs.
• Assessed the impact of creatinine measurement variation on estimated glomerular filtration rate (eGFR) and chronic kidney disease (CKD) staging.

Purpose of the Study:

• Evaluate serum creatinine assay performance across different methodologies and manufacturers.
• Determine the clinical significance of creatinine measurement variability on CKD classification.

Main Methods:

• Included 26 routine instruments representing 13 analyzer types and 6 manufacturers.
• Utilized five serum pools with assigned target values by isotope dilution-gas chromatography/mass spectrometry (ID-GC/MS).

Main Results:

• Higher intra-run coefficients of variation (CV) and bias were observed at low creatinine concentrations.
• Jaffe and enzymatic dry chemistry methods exhibited greater error.
• Calculated eGFR values led to different CKD classifications in 47% of cases.

Conclusions:

• Significant inter-assay differences in creatinine measurements persist despite traceability claims.
• Inaccuracy at low creatinine concentrations poses a risk for clinical misinterpretation in CKD staging.
• Further research is needed to harmonize creatinine measurement methods.