Enzymatic assay for creatinine with fixed-time kinetics on a centrifugal analyzer

Area of Science:

• Clinical Chemistry
• Biochemical Assays
• Enzymatic Analysis

Background:

• Accurate serum creatinine measurement is crucial for diagnosing kidney function.
• Existing methods, like the alkaline picrate procedure, have limitations.
• A need exists for a more efficient and reliable creatinine assay.

Purpose of the Study:

• To develop and validate a novel enzymatic method for serum creatinine determination.
• To assess the performance characteristics of the new assay, including linearity, precision, and interferences.
• To compare the enzymatic method with the established alkaline picrate procedure.

Main Methods:

• Utilized a centrifugal analyzer for automated serum creatinine measurement.
• Employed fixed-time kinetics and a true serum blank for enhanced accuracy.
• Required a small sample volume (100 microliters) of serum.

Main Results:

• The enzymatic method demonstrated linearity up to 90 mg/L.
• Excellent day-to-day precision was observed, with coefficients of variation <7.4% at 6 mg/L and <1.8% at 28 mg/L.
• The assay showed no significant interferences from common substances like bilirubin, hemoglobin, ascorbic acid, and acetoacetic acid.

Conclusions:

• The described enzymatic method provides a fast, precise, and accurate means of measuring serum creatinine.
• This assay is a viable and potentially superior alternative to the conventional alkaline picrate method.
• The method's performance characteristics make it suitable for routine clinical laboratory use.