Diagnostic strategies for C-reactive protein

Area of Science:

• Biochemistry
• Epidemiology
• Clinical Chemistry

Background:

• Serum C-reactive protein (CRP) is a recognized independent risk marker for cardiovascular disease.
• Understanding short-term biological variation in CRP is crucial for accurate risk assessment.
• This study addresses the reliability of single CRP measurements.

Purpose of the Study:

• To document short-term biological variation of C-reactive protein (CRP).
• To propose and test a strategy for assessing the reliability of a single CRP sample.
• To establish re-sampling criteria based on gender and oral contraceptive use.

Main Methods:

• Collected blood samples from healthy men, women not using oral contraceptives (OC-), and women using oral contraceptives (OC+).
• Obtained multiple samples from each participant over a workweek to assess within-subject variation.
• Analyzed data to identify 'suspicious' high CRP values and tested strategies for their detection.

Main Results:

• CRP levels were highest in OC+ women, followed by men, and lowest in OC- women.
• High within-subject coefficients of variation (CVi) were observed for CRP (49.24%) and lnCRP (29.90%).
• A pragmatic strategy using absolute CRP levels stratified by gender and OC-use effectively identified unreliable high values.

Conclusions:

• A single high CRP value necessitates re-sampling if it exceeds specific thresholds.
• Recommended re-sampling thresholds: >1.75 mg/l for men, >1.00 mg/l for OC- women, and >2.00 mg/l for OC+ women.
• These criteria aim to maximize the detection of unreliable high CRP values while minimizing unnecessary repeat testing.