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C-Reactive Protein (CRP)

CRP is a liver-synthesized positive acute-phase protein. It can support assessment of inflammation, but does not identify its source or diagnose malnutrition. High-sensitivity CRP has a separate role in longer-term cardiovascular risk assessment.[1][2]

Biology and Assays​

CRP binds phosphocholine on microbial or damaged-cell surfaces and participates in complement and innate immune responses. IL-6 is a major driver of hepatic synthesis. Hepatic synthesis begins 6 to 8 hours after an inflammatory stimulus, and peak concentrations are reached at about 36 to 50 hours. Serum concentrations can rise up to 1000-fold above physiologic levels. The plasma half-life is approximately 19 hours, and levels fall as the stimulus resolves.[1][3][4] The lag means a very early sample can be falsely reassuring.

Standard CRP and hsCRP measure the same protein. High-sensitivity assays quantify lower concentrations more precisely; detection limits depend on the laboratory platform. Neither an absolute concentration nor a simple range reliably separates bacterial infection from viral disease or sterile postoperative inflammation.[1][5]

For cardiovascular interpretation, hsCRP ≥ 2 mg/L is a risk-enhancing signal. Repeat hsCRP after infection, trauma or surgical recovery resolves when clinically appropriate; the acute result is unsuitable as a stable cardiovascular baseline.[2]

Postoperative Inflammation and Infection​

CRP can help follow a clinical trajectory, but surgery itself raises it. In 51 patients after uncomplicated elective total hip arthroplasty, mean CRP was 13-fold above baseline on day 1 and peaked at 33-fold (10.7 mg/dL) on day 3. It was still 26-fold above baseline on day 7 and 1.9-fold on day 30. Procalcitonin peaked earlier and lower, on day 1 at about 3-fold, and mean values stayed below concentrations typically associated with bacterial infection.[6]

A persistently elevated or rising value may justify reassessment alongside symptoms, examination, vital signs, wound or drain findings and other tests. It does not mandate CT on a particular postoperative day, and a low value cannot safely exclude an early serious complication.[1][7]

For new ICU fever without a clear focus and low to intermediate probability of bacterial infection, SCCM/IDSA 2023 suggests measuring CRP or procalcitonin alongside bedside assessment (weak recommendation, very low-quality evidence).[7] In a high-probability presentation, neither should be used to rule out bacterial infection. The guideline excludes severely immunocompromised patients.[7]

Nutrition and Visceral Proteins​

Inflammation can raise CRP while lowering albumin, prealbumin and transferrin. This explains part of their prognostic association.[8]

In a prospective study of 2,465 emergency department patients, elevated CRP (> 20 mg/L) was the stronger correlate of low albumin (adjusted OR 10.51, 95% CI 7.51–14.72), compared with increased nutritional risk on NRS-2002 (adjusted OR 2.87, 95% CI 1.98–4.15).[9] Each of the three independently predicted 30-day mortality.[9] In 111 older men in a recuperative care unit, markers of inflammation accounted for 56% of the variance in prealbumin change and discharge protein intake for 6%.[10] Monitoring prealbumin change was not an adequate substitute for a detailed nutritional assessment.[10]

PatternInterpretation
Low albumin, high CRPInflammation may contribute; assess nutrition and other causes of low albumin independently
Low albumin, normal CRPConsider synthesis, losses, fluid balance and nutrition
Normal albumin, high CRPInflammation may be present
Both normalNeither result excludes malnutrition or every inflammatory condition

The 2025 GLIM update permits clinical disease burden to establish the inflammatory etiologic criterion. Inflammation identifies the inflammation-associated pathway, while reduced food intake or assimilation is the other GLIM etiologic criterion; inflammation is not required for every malnutrition diagnosis. CRP can clarify uncertainty but is not mandatory. A diagnosis still needs an appropriate phenotypic criterion, such as weight loss, low BMI or reduced muscle mass. Albumin and prealbumin are not GLIM diagnostic criteria.[11]

Cardiovascular Prevention​

The 2025 ACC scientific statement recommends universal hsCRP screening in primary and secondary prevention.[2] If hsCRP is measured, the 2026 ACC/AHA dyslipidemia guideline gives a Class 2a (level B-R) recommendation that high-intensity statin therapy can be useful for adults without ASCVD at borderline 10-year PREVENT-ASCVD risk (3% to <5%) when hsCRP is ≥2 mg/L on two successive occasions with no identifiable cause.[14]

In JUPITER, 17,802 participants without known cardiovascular disease, with LDL cholesterol <130 mg/dL and hsCRP ≥2 mg/L, were randomized to rosuvastatin 20 mg daily or placebo; the trial stopped early after a median 1.9 years of follow-up.[12] The primary composite cardiovascular endpoint was reduced by 44% (HR 0.56, 95% CI 0.46–0.69). The often-quoted 47% reduction concerned the narrower composite of myocardial infarction, stroke or cardiovascular death.[12]

An observational UK Biobank analysis of 448,653 participants without baseline ASCVD found that, in the fully adjusted analysis of 349,725 participants, hsCRP > 3 versus < 1 mg/L was associated with a 34% higher risk of major adverse cardiovascular events, 61% higher cardiovascular death and 54% higher all-cause death.[13]

CRP and Procalcitonin: Practical Differences​

FeatureCRPProcalcitonin
Source during systemic inflammationPredominantly hepatic synthesisExtra-thyroid tissues contribute substantially during systemic bacterial inflammation; thyroid cells alone do not explain the septic response
InterpretationNonspecific inflammatory markerMay support bacterial-infection assessment but is not an independent diagnostic or exclusion test
ConfoundingTissue injury, inflammatory disease, liver dysfunction and timingTissue injury, kidney dysfunction, timing and other noninfectious causes
Cardiovascular usehsCRP has an established risk-assessment roleNo corresponding routine prevention role

Interpret either marker within its clinical setting.[1][7][6]

Application to Reconstruction​

  • After cystectomy with diversion, complex prolapse repair, gender-affirming phalloplasty or vaginoplasty, posterior urethroplasty or free-flap reconstruction, a concerning postoperative course should prompt clinical reassessment for leak, abscess or surgical-site infection. CRP, if measured, is a nonspecific adjunct to symptoms, examination and drain findings.[6][7]
  • Investigate the suspected complication rather than treating the number.
  • In an elective reconstruction workup, screen for nutritional risk, then apply GLIM phenotypic and etiologic criteria when indicated. Use CRP to clarify uncertain inflammatory disease burden; CRP is not required for every GLIM diagnosis.[11]
  • Assess malnutrition independently. Routine paired CRP / prealbumin testing is not a validated method to titrate nutrition or schedule flap surgery.
  • Consider hsCRP within a stable patient's cardiovascular prevention assessment when it would inform risk discussion or lipid management. An hsCRP result obtained during acute illness or postoperative inflammation is not a surgical-clearance threshold.[2]
  • An early infection, or severe hepatic dysfunction that impairs CRP synthesis, can produce a deceptively low result.[1][7][8]

See Also​

References​

1. Lelubre C, Anselin S, Zouaoui Boudjeltia K, Biston P, Piagnerelli M. "Interpretation of C-Reactive Protein Concentrations in Critically Ill Patients." BioMed Research International. 2013;2013:124021. doi:10.1155/2013/124021

2. Mensah GA, Arnold N, Prabhu SD, Ridker PM, Welty FK. "Inflammation and Cardiovascular Disease: 2025 ACC Scientific Statement." Journal of the American College of Cardiology. 2025. doi:10.1016/j.jacc.2025.08.047

3. Olson ME, Hornick MG, Stefanski A, et al. "A Biofunctional Review of C-Reactive Protein (CRP) as a Mediator of Inflammatory and Immune Responses." Frontiers in Immunology. 2023;14:1264383. doi:10.3389/fimmu.2023.1264383

4. Zhou HH, Tang YL, Xu TH, Cheng B. "C-Reactive Protein: Structure, Function, Regulation, and Role in Clinical Diseases." Frontiers in Immunology. 2024;15:1425168. doi:10.3389/fimmu.2024.1425168

5. Ridker PM. "A Test in Context: High-Sensitivity C-Reactive Protein." Journal of the American College of Cardiology. 2016;67(6):712–723. doi:10.1016/j.jacc.2015.11.037

6. Battistelli S, Fortina M, Carta S, et al. "Serum C-Reactive Protein and Procalcitonin Kinetics in Patients Undergoing Elective Total Hip Arthroplasty." BioMed Research International. 2014;2014:565080. doi:10.1155/2014/565080

7. O'Grady NP, Alexander E, Alhazzani W, et al. "Society of Critical Care Medicine and the Infectious Diseases Society of America Guidelines for Evaluating New Fever in Adult Patients in the ICU." Critical Care Medicine. 2023;51(11):1570–1586. doi:10.1097/CCM.0000000000006022

8. Evans DC, Corkins MR, Malone A, et al. "The Use of Visceral Proteins as Nutrition Markers: An ASPEN Position Paper." Nutrition in Clinical Practice. 2021;36(1):22–28. doi:10.1002/ncp.10588

9. Eckart A, Struja T, Kutz A, et al. "Relationship of Nutritional Status, Inflammation, and Serum Albumin Levels During Acute Illness: A Prospective Study." American Journal of Medicine. 2020;133(6):713–722.e7. doi:10.1016/j.amjmed.2019.10.031

10. Dennis RA, Johnson LE, Roberson PK, et al. "Changes in Prealbumin, Nutrient Intake, and Systemic Inflammation in Elderly Recuperative Care Patients." Journal of the American Geriatrics Society. 2008;56(7):1270–1275. doi:10.1111/j.1532-5415.2008.01789.x

11. Jensen GL, Cederholm T, Correia MITD, et al. GLIM consensus approach to diagnosis of malnutrition: A 5-year update. JPEN J Parenter Enteral Nutr. 2025. doi:10.1002/jpen.2756.

12. Ridker PM, Danielson E, Fonseca FAH, et al. Rosuvastatin to prevent vascular events in men and women with elevated C-reactive protein. N Engl J Med. 2008;359:2195–2207. doi:10.1056/NEJMoa0807646.

13. Kurt B, Reugels M, Schneider KM, et al. "C-Reactive Protein and Cardiovascular Risk in the General Population." European Heart Journal. 2025;ehaf937. doi:10.1093/eurheartj/ehaf937

14. Blumenthal RS, Morris PB, Gaudino M, et al. "2026 ACC/AHA/AACVPR/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Dyslipidemia: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines." Circulation. 2026;153(17):e1154–e1276. doi:10.1161/CIR.0000000000001423