In an otherwise asymptomatic adult with a mildly elevated C‑reactive protein (0.3–1.0 mg/dL), how often should the test be repeated?

Retesting Mildly Elevated CRP in Asymptomatic Adults

In an asymptomatic adult with mildly elevated CRP (0.3–1.0 mg/dL or 3–10 mg/L), repeat the test in 2 weeks and average the two measurements to obtain a stable cardiovascular risk assessment. 1, 2

Initial Retesting Strategy

• Repeat CRP measurement in 2 weeks to confirm the elevation and rule out transient causes, as recommended by the American Heart Association 1, 2
• Average the two measurements taken 2 weeks apart for stable cardiovascular risk stratification 1, 2
• This approach accounts for the significant within-person variability of CRP over short time periods 3

Interpretation After Repeat Testing

Once you have averaged two measurements:

• Low cardiovascular risk: <1.0 mg/L 1, 2
• Average cardiovascular risk: 1.0–3.0 mg/L 1, 2
• High cardiovascular risk: >3.0 mg/L 1, 2

For patients with values consistently in the 3–10 mg/L range (your specified mild elevation), this places them in the high cardiovascular risk category and may warrant consideration for statin therapy if they have intermediate cardiovascular risk by traditional criteria 2.

Long-Term Monitoring Intervals

After establishing a stable baseline with two measurements:

• Repeat testing every 3 years is reasonable for ongoing cardiovascular risk assessment in asymptomatic individuals 3
• This interval aligns with recommendations for other cardiovascular risk markers like blood lipids and blood pressure 3
• CRP shows moderate-to-good stability over 6 months to 3 years (correlation coefficients 0.65–0.88), approximating the stability of other cardiovascular risk markers 3

Critical Pitfalls to Avoid

• Do not assume a single measurement represents stable individual differences – CRP can fluctuate significantly with transient exposures like acute stress, minor infections, or environmental irritants 3, 4
• Approximately 20% of smokers have CRP >10 mg/L from smoking alone, so document smoking status 3, 2
• Obesity, age, sex, race, and socioeconomic status significantly affect baseline CRP levels – 30–40% of US adults have CRP >3 mg/L, far higher than historical reference populations 3, 2
• If either measurement exceeds 10 mg/L, discard the cardiovascular risk assessment approach and instead evaluate for active infection or inflammatory disease 1, 2

When to Investigate Further

If CRP remains persistently elevated (>3 mg/L) on repeat testing:

• Systematically screen for infection sources (respiratory, urinary, soft tissue, abdominal) 2, 5
• Check complete blood count, liver function tests, and consider inflammatory conditions 2, 5
• Document recent trauma, surgery, or known inflammatory conditions 2, 5
• If no obvious cause is identified and CRP remains 3–10 mg/L, repeat measurement in 3–6 months while monitoring for emerging symptoms 1, 5