Use of a quality-control plasma sample to decrease interassay variation in radioimmunoassays of apolipoprotein A-I.

Area of Science:

• Biochemistry
• Immunology
• Clinical Chemistry

Background:

• Apolipoprotein A-I (apo A-I) is crucial for high-density lipoprotein function.
• Accurate quantification of apo A-I is essential for cardiovascular disease risk assessment.
• Radioimmunoassays are common methods for protein quantification but can be affected by reagent stability.

Purpose of the Study:

• To establish and validate a radioimmunoassay for quantifying apolipoprotein A-I (apo A-I) in human plasma.
• To investigate and mitigate interassay variation caused by labeled antigen degradation.
• To assess the efficacy of using a pooled plasma sample as a secondary standard.

Main Methods:

• Development of a radioimmunoassay using purified apo A-I as the primary standard.
• Implementation of a pooled plasma sample as a secondary quality-control standard.
• Measurement of apo A-I in plasma samples from 16 subjects over four months and in a pooled plasma sample over ten months.

Main Results:

• Measured apo A-I values showed an increasing trend over time due to labeled antigen degradation.
• The use of a quality-control plasma sample significantly decreased interassay variation.
• This reduction in variation was observed despite the ongoing degradation of the labeled antigen.

Conclusions:

• A radioimmunoassay for apo A-I quantification can be improved by incorporating a secondary quality-control plasma standard.
• This quality-control approach effectively compensates for variations introduced by labeled antigen degradation.
• The validated method provides a more reliable measurement of apo A-I levels in plasma samples.