Normal Values
- Post-spinal surgery, it peaks at 15 ± 25 a few days after OR
- Post-stroke, it can go up to 25 ± 10
- Post-TKA, it can go up to 155 mg/L
Interpretation
- The higher the value, the more likely to be a bacterial infection
Comparison to ESR
| ESR | CRP | Clinical Scenarios |
|---|---|---|
| high | low | rheumatoid arthritis, infection, low albumin elevated creatinine |
| low | high | low albumin |
- CRP less effected by older age than ESR
Further Reading
Spine
- Serum C-reactive protein levels correlate with clinical response in patients treated with antibiotics for wound infections after spinal surgery. Spine J. 2006;6(3):311-315.
- CRP better than ESR
Joints
- Serial measurement of the C-reactive protein is a poor predictor of treatment outcome in prosthetic joint infection. J Antimicrob Chemo. 2011;66(7);1590-1593.
- Although the population of patients with failure had higher CRP on average, CRP measurement was not useful for predicting failure in individual patients.
- C-Reactive Protein, Erythrocyte Sedimentation Rate and Orthopedic Implant Infection. PLoS ONE. 2010:5(2):e9358.
- ESR and CRP have poor Sn and Sp for diagnosing hardware infections
- C-reactive protein may misdiagnose prosthetic joint infections, particularly chronic and low-grade infections. International Orthopaedics. 2017.
- 1/3 of culture-positive PJIs had normal CRP and 1/4 had normal ESR.
- Most common associated organisms were coagulase-negative staphylococci and C. acnes
- Seronegative infections in hip and knee arthroplasty: periprosthetic infections with normal erythrocyte sedimentation rate and C-reactive protein level
- 4% of PJI have normal CRP and ESR
- CoNS was more common, Staph. aureus less common
Other
- Prognostic Value of Serial C-Reactive Protein Measurements in Left-Sided Native Valve Endocarditis. Arch Intern Med. 2008;168(3):302-307.
- After 1 week following starting therapy, a CRP over 122 predicts failure (OR 10)
- Utility of C-reactive protein measurements for empyema diagnosis after pneumonectomy. Annals Thoracic Surg. 1994;57(4):933-936.
- Post-operative rise or high-plateau of CRP predicted postoperative infection (empyema)
- Diagnostic Accuracy of C-reactive Protein for Intraabdominal Infections After Colorectal Resections. J Gastrointest Surg. 2009;13(9):1599-1606.
- Post-resection day 3 (or 5 or 7) CRP predicts intraabdominal infection, with Sn 82% and Sp 73% using a cutoff of 190 mg/L (normal <10)
