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Diagnostic strategies for C-reactive protein
Harriëtte Riese1, Tanja G M Vrijkotte, Piet Meijer
1Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands. h.riese@psy.vu.nl
Insights
Serum C-reactive protein (CRP) is a cardiovascular disease risk marker. This study proposes re-sampling criteria for unreliable high CRP values to improve cardiovascular risk assessment accuracy.
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.
Background:
Serum C-reactive protein (CRP) has been identified in prospective epidemiological research as an independent risk marker for cardiovascular disease. In this paper, short-term biological variation of CRP is documented and a strategy to test the reliability of a single CRP sample is proposed.
Methods:
Data were obtained from three groups of healthy volunteers: men, no oral contraceptives (OC-)using women and OC-using women. Blood samples were obtained 3 times in men and twice in women during a workweek.
Results And Discussion:
CRP values were highest in the OC-using women, followed by the men, and lowest in the no OC-using women. Averaged over the three groups the within-subject coefficients of variation (CVi) was 49.24% for CRP, and 29.90% for lnCRP. Using the repeated measures, individual samples were identified that reflected a 'suspicious' unreliable high value, i.e. a value that was more than 2 standard deviations higher than the lowest value obtained from the same subject. In an a posteriori analysis, three strategies to identify these suspicious high CRP values were then tested. In terms of maximizing detection of suspicious values and minimizing unnecessary resampling, best results were obtained for the most pragmatic criterion of using an absolute level, stratified for gender, and OC-use, to decide whether a second sample should be obtained.
Conclusion:
A single high CRP value must be followed by re-sampling when it is above 1.75 mg/l for men, above 1.00 mg/l for no OC-using women, and above 2.00 mg/l for OC-using women.