Inflammation Unveiled: The CRP Blood Test and Its Role in Health Assessment

What is C-reactive Protein?

C-reactive protein (CRP) is a type of pentameric protein that is synthesised by the liver. Its level rises as a response to fight inflammation in the body. CRP is an acute-phase reactant protein discovered by Tillett and Francis in 1930.It was identified initially as a substance in the serum of patients with acute inflammation. This substance was found to react with the "C" Carbohydrate Antigen of the capsule of pneumococcus, and hence it was named CRP.

CRP has both proinflammatory and anti-inflammatory properties. It plays an important role in recognising and clearing foreign pathogens along with damaged cells. When it is activated by autoantibodies, this can become pathologic. It can also lead to increased tissue damage in certain cases by activation of the complement system, leading to inflammatory cytokines.

What can cause CRP to increase?

There are many reasons that lead to increased C-reactive protein.Acute and chronic conditions that are infectious or non-infectious in etiology could cause an elevated CRP. Infectious conditions can significantly increase CRP levels in most cases, while a minor increase in CRP levels could be attributed to a broader spectrum of etiologies, including sleep disturbances and periodontal disease.

Indications

A physician may prescribe the CRP test when he/she suspects acute or chronic inflammation like SLE or rheumatoid arthritis [RA]) or infection. It has been found that there is some link between cardiovascular risk and elevated hs-CRP, but this application is under evaluation due to the poor specificity of this test.

How to interpret the CRP levels ??

· Hs-CRP is usually reported in mg/dL.

· Hs-CRP levels less than 1 mg/dL are considered low risk when used for cardiac risk stratification. The range indicating moderate risk is levels between 1 mg/dL and 3 mg/dL.

· Persons with hs-CRP levels greater than 3 mg/dL are at high risk for the development of cardiovascular disease.

Interpretation of CRP levels:

·  Less than 0.3 mg/dL: Normal (level seen in most healthy adults).

·  0.3 to 1.0 mg/dL: Normal or minor elevation (can be seen in gingivitis, obesity, pregnancy, depression, diabetes, cigarette smoking, common cold, periodontitis, genetic polymorphisms and sedentary lifestyle).

· 1.0 to 10.0 mg/dL: Moderate elevation (Systemic inflammation such as RA, SLE, malignancies, or other autoimmune diseases, pancreatitis, myocardial infarction, bronchitis).

· More than 10.0 mg/dL: Marked elevation (Viral infections, acute bacterial infections, major trauma, systemic vasculitis).

· More than 50.0 mg/dL: Severe elevation (Acute bacterial infections).

What factors could be responsible for variations in CRP test results???

There could be a false decrease in CRP levels due to certain medications such as non-steroidal anti-inflammatory drugs (NSAIDs), statins and magnesium supplementation. Other factors like recent injury or illness can result in false elevation, particularly at the time of cardiac risk stratification.

Mild elevations in CRP Test could also be observed even without any systemic or inflammatory disease. Older patients and females generally have higher levels of CRP. Diabetes, obesity, depression, insomnia, and smoking are some other factors that contribute to mild elevations in CRP. Individuals with these comorbidities should exercise caution while interpreting the results.

How is the CRP blood test used for the assessment of health:

1. Detecting Inflammation:

●       Acute Inflammation: CRP levels can rise significantly in response to acute inflammation, such as an infection or injury.

●       Chronic Inflammation: Persistently elevated CRP levels may indicate chronic inflammation, which can contribute to long-term health issues.

2. Cardiovascular Risk Assessment:

●       Elevated CRP levels are associated with an increased risk of cardiovascular disease. It is believed that inflammation plays a role in the development and progression of atherosclerosis (hardening of the arteries), which can lead to heart attacks and strokes.

3. Monitoring Chronic Conditions:

●       CRP levels can be monitored in individuals with chronic inflammatory conditions like rheumatoid arthritis or lupus to assess disease activity.

4. Post-Surgery Monitoring:

●       After surgery, CRP levels may rise as part of the normal healing process. Monitoring CRP can help healthcare providers assess how well the body is recovering.

5. Assessing Response to Treatment:

●       In some cases, the CRP blood test is used to monitor how well a patient is responding to treatment for inflammatory conditions.

6. Screening for Infection:

●       CRP levels can be elevated in response to infections. The test may be used alongside other diagnostic tools to identify the presence and severity of infections.

7. Cancer Assessment:

●       Elevated CRP levels have been associated with certain cancers. However, CRP alone is not specific enough to diagnose cancer, and further testing is usually needed

8. Autoimmune Diseases:

●       In autoimmune diseases like lupus or rheumatoid arthritis, where the immune system attacks the body's own tissues, CRP levels can be elevated.

Important Considerations:

●       Non-Specific Marker: While CRP Test is a useful marker of inflammation, it is not specific to any particular disease. Additional tests and clinical evaluation are often needed for a complete diagnosis.

●       Other Factors: CRP levels can be influenced by factors such as age, gender, and lifestyle. Smoking and obesity, for example, can elevate CRP levels.

In summary, the CRP blood test is a valuable tool in assessing inflammation in the body and plays a crucial role in the management of various health conditions. It's important to note that while CRP Test is a useful indicator, it is part of a comprehensive health assessment that includes other clinical information and tests.

References

●        Cleland DA, Eranki AP. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Apr 23, 2023. Procalcitonin.

●        Jungen MJ, Ter Meulen BC, van Osch T, Weinstein HC, Ostelo RWJG. Inflammatory biomarkers in patients with sciatica: a systematic review. BMC Musculoskelet Disord. 2019 Apr 09;20(1):156.

●        Kramer NE, Cosgrove VE, Dunlap K, Subramaniapillai M, McIntyre RS, Suppes T. A clinical model for identifying an inflammatory phenotype in mood disorders. J Psychiatr Res. 2019 Jun;113:148-158.

●        Vanderschueren S, Deeren D, Knockaert DC, Bobbaers H, Bossuyt X, Peetermans W. Extremely elevated C-reactive protein. Eur J Intern Med. 2006 Oct;17(6):430-3.

●        Eschborn S, Weitkamp JH. Procalcitonin versus C-reactive protein: review of kinetics and performance for diagnosis of neonatal sepsis. J Perinatol. 2019 Jul;39(7):893-903

●        Darooghegi Mofrad M, Milajerdi A, Koohdani F, Surkan PJ, Azadbakht L. Garlic Supplementation Reduces Circulating C-reactive Protein, Tumor Necrosis Factor, and Interleukin-6 in Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials. J Nutr. 2019 Apr 01;149(4):605-618.

●        Dick AG, Magill N, White TCH, Kokkinakis M, Norman-Taylor F. C-reactive protein: what to expect after bony hip surgery for nonambulatory children and adolescents with cerebral palsy. J Pediatr Orthop B. 2019 Jul;28(4):309-313.

●        Lee Y, McKechnie T, Doumouras AG, Handler C, Eskicioglu C, Gmora S, Anvari M, Hong D. Diagnostic Value of C-Reactive Protein Levels in Postoperative Infectious Complications After Bariatric Surgery: a Systematic Review and Meta-Analysis. Obes Surg. 2019 Jul;29(7):2022-2029.

●        Johns I, Moschonas KE, Medina J, Ossei-Gerning N, Kassianos G, Halcox JP. Risk classification in primary prevention of CVD according to QRISK2 and JBS3 'heart age', and prevalence of elevated high-sensitivity C reactive protein in the UK cohort of the EURIKA study. Open Heart. 2018;5(2):e000849.