Aqueous primary standard for use in measuring cholesterol by the cholesterol oxidase method

Area of Science:

• Clinical Chemistry
• Biochemical Analysis
• Analytical Standards

Background:

• Accurate cholesterol measurement is crucial for diagnosing cardiovascular diseases.
• Existing cholesterol standards often use organic solvents, posing challenges for aqueous enzymatic assays.
• There is a need for a stable, aqueous primary standard for cholesterol determination.

Purpose of the Study:

• To develop and validate an aqueous cholesterol standard for enzymatic cholesterol measurement.
• To assess the performance characteristics of the novel aqueous standard.
• To evaluate its suitability for routine clinical laboratory use.

Main Methods:

• Cholesterol was solubilized in an aqueous solution containing sodium deoxycholate and saline.
• Concentrations of crystalline cholesterol (1.00–5.00 g/L) were prepared and analyzed.
• Measurements were performed using a cholesterol oxidase enzymatic procedure on a centrifugal analyzer.
• The aqueous standard was compared against a commercial isopropanol-based standard.
• Stability, linearity, precision, and viscosity were evaluated.

Main Results:

• The sodium deoxycholate solubilizer did not interfere with cholesterol measurement.
• The aqueous standard showed excellent correlation (r = 0.986) with a commercial standard.
• High linearity was observed up to 5.00 g/L.
• Low day-to-day variation (CV < 4%) was achieved for cholesterol concentration in reference sera.
• The standard demonstrated good stability when stored at room temperature for 360 days.
• The mixture's viscosity was comparable to human serum.

Conclusions:

• The developed aqueous cholesterol standard is effective for enzymatic cholesterol assays.
• It offers a stable, reliable, and accurate alternative to organic solvent-based standards.
• This standard is suitable for routine use in clinical chemistry laboratories for cholesterol quantification.