hs-CRP Testing in Cardiovascular Risk Assessment
hs-CRP testing should be selectively used in patients at intermediate cardiovascular risk (10-20% 10-year risk) to guide decisions about intensifying preventive therapy, but it is not recommended for routine screening in all patients or as a treatment target. 1, 2
When to Measure hs-CRP
Measure hs-CRP specifically in intermediate-risk patients (10-20% 10-year CHD risk by Framingham or similar calculators) when you need additional information to decide whether to initiate or intensify statin therapy or other preventive interventions. 1, 2 This is a Class IIa recommendation from the American Heart Association/CDC, meaning it is reasonable to perform and likely beneficial. 1
Do not routinely measure hs-CRP in:
- Low-risk patients (<10% 10-year risk) - they won't benefit from reclassification 1
- High-risk patients (>20% 10-year risk) - they already warrant aggressive therapy regardless of hs-CRP 1
- The general population as a screening tool - insufficient evidence supports this approach 1, 3
Interpreting hs-CRP Results
Risk stratification thresholds: 2
- <1.0 mg/L = Low cardiovascular risk
- 1.0-3.0 mg/L = Average/moderate cardiovascular risk
- >3.0 mg/L = High cardiovascular risk (approximately 2-fold increased relative risk)
Critical action point: If hs-CRP is persistently >10 mg/L after repeat testing in 2 weeks, stop and evaluate for non-cardiovascular causes of inflammation such as infection, autoimmune disease, or malignancy before attributing it to cardiovascular risk. 1, 2 This is essential to avoid misclassifying patients with acute inflammatory conditions.
Clinical Decision Algorithm
Step 1: Calculate 10-year cardiovascular risk using Framingham or pooled cohort equations. 2
Step 2: If intermediate risk (10-20%), measure hs-CRP to refine risk assessment. 1
Step 3: Interpret results in context:
- hs-CRP >3 mg/L in intermediate-risk patients: Consider reclassifying to higher risk and intensifying therapy (statins, aspirin, aggressive lifestyle modification). 1, 2 The 2013 ACC/AHA guideline notes that hs-CRP can lead to reclassification in intermediate-risk persons, though the magnitude of net benefit remains somewhat uncertain. 1
- hs-CRP 1-3 mg/L: Maintain standard intermediate-risk management.
- hs-CRP <1 mg/L: May support less aggressive intervention in borderline cases.
Step 4: Focus treatment on comprehensive cardiovascular risk reduction, not on lowering hs-CRP itself. 2
What hs-CRP Does and Does Not Do
hs-CRP provides additive predictive value beyond traditional Framingham risk factors for future cardiovascular events in women and older adults, even after extensive adjustment for other risk factors. 1 The USPSTF found strong evidence that CRP is associated with CHD events and moderate evidence that adding CRP to risk models improves risk stratification in intermediate-risk persons. 1
However, hs-CRP does not:
- Reliably predict the extent of angiographic atherosclerosis 1
- Serve as a treatment target - never use serial hs-CRP testing to monitor therapy effects (Class III recommendation) 2
- Replace comprehensive risk assessment - it only supplements it 1
Treatment Implications of Elevated hs-CRP
Statin therapy is the primary intervention for patients with elevated hs-CRP in the intermediate-risk category. 2 Post-hoc analyses from the CARE trial suggest patients with elevated hs-CRP derive greater absolute risk reduction from statins, though this was not a pre-specified endpoint. 1, 2
Aspirin may provide greater benefit in patients with elevated hs-CRP based on subset analyses from the Physicians' Health Study. 2
Lifestyle modifications (weight loss, exercise) have been associated with hs-CRP reductions in observational studies, and may help motivate patients, though prospective randomized evidence for this strategy is lacking. 1, 2
Role in Secondary Prevention
In patients with established coronary disease or acute coronary syndromes, elevated hs-CRP (particularly >10 mg/L) predicts recurrent MI and mortality independent of troponin levels. 1, 2 However, secondary prevention measures should be implemented based on the presence of disease itself, not contingent on hs-CRP levels (Class III recommendation). 2
Critical Pitfalls to Avoid
Never treat hs-CRP as an isolated target. The goal is comprehensive cardiovascular risk reduction, not lowering hs-CRP numbers. 2 No prospective randomized trials demonstrate that treating to lower hs-CRP improves outcomes. 1
Do not use serial hs-CRP measurements to monitor treatment response - this is explicitly not recommended (Class III). 2
Do not measure hs-CRP during acute illness - wait until the patient is clinically stable, as acute infections and inflammatory conditions will spuriously elevate levels. 1
Recognize the limitations: The 2013 ACC/AHA guideline acknowledges that while hs-CRP shows association with CHD and leads to some reclassification, the evidence does not definitively support routine use, and updated systematic reviews addressing discrimination, calibration, and cost-effectiveness are needed. 1