Reagent | C-Reactive Protein (CRP)
C-Reactive Protein (CRP): The Most Sensitive Acute Phase Reactant
Benefits of the Randox Assay
The Randox CRP assay has shown to have limited interference from conjugate and free bilirubin, haemoglobin, Intralipid® and triglycerides.
Wide measuring range
The Randox CRP assay has a measuring range of 2.88 – 220 mg/l for the comfortable detection of clinically important results.
The Randox CRP assay is available in a liquid ready-to-use format for convenience and ease-of-use.
Stable to expiry
The Randox CRP assay is stable to expiry when stored at +2oC to +8oC.
Dedicated calibrator and controls available
Dedicated CRP calibrator and controls available offering a complete testing package.
Applications available detailing instrument-specific settings for the convenient use of the Randox CRP assay on a variety of clinical chemistry analysers.
Instrument Specific Applications (ISA’s) are available for a wide range of biochemistry analysers. Contact us to enquire about your specific analyser.
C-reactive protein (CRP) is the dominant acute phase protein in mammals 1. Elevated levels of CRP are not disease specific but are synthesised, by hepatocytes, in response to pro-inflammatory cytokines during inflammatory and/or infectious processes 2, 3. The physiological function of CRP is the enhancement of cell-mediated immunity through the promotion of phagocytosis, accelerated chemotaxis and the activation of platelets 1.
Known as a biomarker of acute inflammation, many large-scale prospective studies demonstrate the association between CRP and chronic inflammation, including: cardiovascular disease (CVD), cerebrovascular accident (CVA) (ischaemic stroke), Alzheimer’s Disease, and age-related macular degeneration 2.
CRP is a major cardiovascular disease (CVD) risk factor. A CRP level of >10mg/l correlates with a >4% risk of developing a fatal CVD event in 10 years, including: myocardial infarction, peripheral arterial disease, stroke and sudden cardiac death. Inflammation is an integral part in the development and rapid progression of coronary heart disease (CHD) 4.
The coronary artery disease (CAD) process is characterised by increasing levels of inflammatory biomarkers. CRP is not only an excellent biomarker or mediator of atherosclerosis but is a strong independent marker in the prediction of adverse CV events, including: myocardial infarction, ischaemic stroke, and sudden cardiac death. CPR can be utilised as a clinical guide for the diagnosis, management and prognosis of CVD 5.
The development of a cerebrovascular accident (CVA) (stroke) is the result of longstanding vascular inflammation, thrombosis, plaque rupture and subsequent brain ischaemia or infarction. Elevated CRP levels is associated with the development of CVA 6.
High sensitivity CRP (hsCRP) plays an important role in the early diagnosis, prognosis, long and short death risk and prediction of etiological subtypes of stroke 7. Find out more about the Randox hsCRP assay.
Alzheimer’s disease (AD) is the most common form of dementia, accounting for 60-80% of dementia cases 7. CRP is believed to be involved in the pathophysiology of cerebral small vessel disease (CSVD) and neurodegeneration 8. CRP levels are associated with cognitive impairment 9. Inflammation should be considered as a target treatment, with the aim of delaying the progression of subclinical brain damage and cognitive decline 8. Midlife elevations in CRP are associated with an increased risk of developing AD. Patients with AD, CRP elevations continues to predict increased dementia severity suggestive of a possible pro-inflammatory endophenotype in AD 10.
In COVID-19 patients, CRP testing has proved to perform well in discriminating disease severity and predicting adverse outcomes 11. CRP levels positively correlates with lung lesions, reflecting disease severity, and should be considered a key indicator in disease monitoring (see fig. 1) 12.
CRP levels are associated with computed tomography (CT) scores and COVID-19 disease development, with CRP levels increasing in the initial stage of severe COVID-19, prior to the CT findings 13.
Elevated CRP levels have been identified in 86% of patients admitted to hospital. CRP measurements are useful in diagnosis, assessing prognosis and monitoring for clinical improvements or deterioration 14.
Fig. 1. Relation between CRP levels, clinical severity, and lung lesions 12
Specific Protein EQA
 Thanoon IAJ, Abdul-Jabber HAS, Taha DA. Oxidative Stress and C-Reactive Protein in Patients with Cerebrovascular Accident (Ischaemic Stroke) The role of Ginkgo biloba extract. Sultan Qaboos University Medical Journal 2012; 12(2): 197-205.
 Cozlea DL, Farcas DM, Nagy A, Keresztesi AA, Tifrea R, Cozlea L, Carasca E. The Impact of C Reactive Protein on Global Cardiovascular Risk on Patients with Coronary Artery Disease. Current Health Sciences Journal 2013; 39(4): 225-231.
 Avan A, Tavakoly Sany SB, Ghayour-Mobarhan M, Rahimi HR, Tajfard M, et al. Serum C‐reactive protein in the prediction of cardiovascular diseases: Overview of the latest clinical studies and public health practice. Journal of Cellular Physiology 2018; 223(11): 1-18.
 Yu H, Huang Y, Chen XY, Nie WB, Wang YJ, Jiao Y, et al. High-sensitivity C-reactive protein in stroke patients – The importance in consideration of influence of multiple factors in the predictability for disease severity and death. Journal of Clinical Neuroscience 2017; 36(2017): 12-19.
 Hilal S, Ikram MA, Verbeek MM, Franco OH, Stoops E, Vanderstichele H, et al. C-Reactive Protein, Plasma Amyloid-β Levels, and Their Interaction With Magnetic Resonance Imaging Markers. Stroke 2018; 49(11): 2692-2698.
 Watanabe Y, Kitamura K, Nakamura K, Sanpei K, Wakasugi M, Yokoseki A, et al. Elevated C-Reactive Protein Is Associated with Cognitive Decline in Outpatients of a General Hospital: The Project in Sado for Total Health (PROST). Dementia and Genetic Cognitive Disorders 2016; 6(): 10-19.
 O’Bryant SE, Waring SC, Hobson V, Hall JR, Moore CB, Bottiglieri T, et al. Decreased C-Reactive Protein Levels in Alzheimer Disease. Journal of Geriatric Psychiatry and Neurology 2011; 23(1): 49-53.
 Tan C, Huang Y, Shi F, Tan K, Ma Q, Chen Y, et al. C‐reactive protein correlates with computed tomographic findings and predicts severe COVID‐19 early. Journal of Medical Virology 2020; 92(7): 856-862.
 The Royal College of Pathologists. Guidance on the use and interpretation of clinical biochemistry tests in patients with COVID-19 infection. https://www.rcpath.org/uploads/assets/3f1048e5-22ea-4bda-953af20671771524/G217-RCPath-guidance-on-use-and-interpretation-of-clinical-biochemistry-tests-in-patients-with-COVID-19-infection.pdf (accessed 14 June 2020).
What are inflammatory biomarkers?
The purpose of measuring an inflammatory biomarker is to detect inflammation, which can assist clinicians in the identification of a particular disease or provide a marker of treatment response. Inflammation, either chronic or acute, is the body’s immune response to protect against harmful stimuli such as damaged cells, irritants or pathogens.1 When inflammation occurs in the body, extra protein is released from the site of inflammation and circulates in the bloodstream.2 It is these proteins, or antibodies, which clinicians are testing for in the blood as they can indicate if inflammation is present.
Like many inflammatory biomarkers, such as rheumatoid factor (RF), C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR), further tests will be required as testing for these tests alone does not provide a clearly defined diagnosis. However inflammatory biomarker tests can provide clinicians with a good indication of what may be wrong with a patient, which is why they are commonly tested for in a clinical setting.
What is Rheumatoid Factor?
Rheumatoid factor (RF) is an autoantibody which can target and damage healthy body tissue and in turn cause inflammatory symptoms.3 It is uncommon for this antibody to be present in healthy individuals, which is why it is a beneficial test to aid the diagnostic process. In particular, rheumatoid factor can be used as an inflammatory biomarker to assist in the diagnosis of rheumatoid arthritis (RA). However the rheumatoid factor antibody can also be present in healthy individuals or patients with systemic lupus erythematosus, liver cirrhosis, Sjögren’s Syndrome, Hepatitis and other conditions.4 If a test detects rheumatoid factor levels above 14 IU/ml, this is considered abnormally high.3
What is Rheumatoid Arthritis?
Rheumatoid arthritis is an autoimmune disease which attacks the lining tissue of joints, resulting in chronic inflammation. This disease commonly affects the hands, feet and wrists, with symptoms causing pain, fatigue and loss of bodily function and over time may even lead to multiple organ damage.5 Although diagnosis of rheumatoid arthritis requires a physical examination, testing for rheumatoid factor can be beneficial to assist in the diagnosis of this disease. Other blood tests that can be used to detect biomarkers associated with rheumatoid arthritis include C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), IgA, IgG, IgM and anti-cyclic citrullinated peptide (anti-CCP).
For health professionals
Randox Laboratories offer a leading portfolio of diagnostic reagents which includes a test for rheumatoid factor, with applications available for a range of biochemistry analysers. With a measuring range of 6.72 – 104 lU/ml, this assay can comfortably detect levels outside the normal range. Randox offer a complete diagnostic package for the screening of rheumatoid factor with a range of kit sizes, controls and calibrators available. Other inflammatory biomarker tests available from Randox include CRP, High Sensitivity CRP, Full Range CRP, IgA, IgG and IgM.
1. Nordqvist, C. Inflammation: Causes, Symptoms and Treatment. Medical News Today, https://goo.gl/rT4WS9 (accessed 16 January 2017)
2. Harding, M., Blood Tests to Detect Inflammation, Patient, 2015, https://goo.gl/F4OGrz, (accessed 16 January 2017)
3. Shiel, W. C., Rheumatoid Factor (RF), MedicineNet, 2016, https://goo.gl/XPA69u 2016 (accessed 16 January 2017)
4. Rheumatoid Arthritis Organisation, Rheumatoid Factor Test, Rheumatoid Arthritis Organisation, 2016, https://goo.gl/JujE5a
5. Gibofsky, A. Overview of Epidemiology, Pathophysiology and Diagnosis of Rheumatoid Arthritis. The American Journal of Managed Care. Vol.18, No.13. p.295-302, 2012
An inflammatory biomarker detects inflammation in the body. Inflammation is not just the immediate, short-term response of the body to an injury or infection. Inflammation within the body can be a long-term, chronic condition resulting in a number of health implications. In diagnostics, measurement of an inflammatory biomarker can not only detect acute inflammation but provide a marker of treatment response.
C-reactive protein (CRP) is an acute phase protein produced by the liver in response to inflammation, infection and tissue injury. CRP is a particularly beneficial inflammatory biomarker as it is detected much faster than other markers in the blood. Levels of CRP increase when inflammation occurs and therefore it can be a significant biomarker in a range of diseases, including the following.
An increasing amount of research exists to suggest CRP is not only a useful, non-specific inflammatory biomarker, but it may have a direct influence on coronary heart disease and cardiac events1. Inflammation can occur when LDL cholesterol builds up in the artery walls causing atherosclerosis. Modifiable risk factors of atherosclerosis include smoking, diabetes, poor diet, high blood pressure and physical inactivity, all factors which subsequently increase the risk of heart attacks, ischemic stroke, peripheral artery disease and even vascular dementia2,3.
Studies have also shown that persistent low levels of CRP can contribute to a person developing CVD. Therefore using high sensitivity CRP as an inflammatory biomarker can detect low levels, helping to predict the likelihood of a patient developing CVD in the future.
Research suggests that inflammation in the body can influence the development of type 2 diabetes. With the ability to be managed through diet and exercise, type 2 diabetes is commonly associated with obesity. Research has shown that excess body fat can cause continuous chronic low-grade inflammation as a result of inflammatory cytokines and increased plasma levels of CRP. As a result, this chronic inflammation has the ability to cause insulin resistance leading to the development of type 2 diabetes4.
A three year study which analysed the bone and joint health of 10,000 patient samples in India has found that inflammatory biomarkers, in particular CRP and ESR (Erythrocyte Sedimentation Rate) were raised in most of the samples compared to any other markers5. Although CRP is a non-specific inflammatory biomarker, it can be used alongside other tests, such as Rheumatoid Factor, to diagnose inflammatory joint diseases such as Rheumatoid Arthritis. Not only will CRP levels be higher due to chronic inflammation, but CRP levels can be monitored to assess levels of inflammation over time, allowing clinicians offer effective treatment.
Chronic Obstructive Pulmonary Disease (COPD)
COPD is a condition associated with inflammation of the lungs and airways. Studies have shown that measuring CRP levels is beneficial to detect exacerbations, when symptoms of COPD get suddenly worse and can last for several days. This is because CRP levels spike when exacerbations happen, causing lung function to deteriorate6.
Neonatal Bacterial Infections
CRP is one of the preferred and frequently used tests in neonatal units when diagnosing suspected bacterial infections, such as neonatal sepsis, in newborns who show signs on infection. Due to delayed synthesis during the inflammatory response, the sensitivity of CRP is lowest during early stages of infection. It is therefore critical that extremely low levels of CRP can be detected during diagnosis to distinguish whether symptoms are related to an infectious or non-infectious condition. This early detection then allows for rapid and appropriate neonatal treatment7.
Inflammatory Bowel Disease
Research suggests that using CRP as an inflammatory biomarker can help distinguish between Inflammatory Bowel Disorder (IBD) and Irritable Bowel Syndrome (IBS)8. Although IBD and IBS have some similarities in symptoms, IBD causes chronic inflammation, whereas IBS is a non-inflammatory condition. Therefore using CRP as a biomarker can allow clinicians to deliver a confident and accurate diagnosis.
For health professionals
Randox Laboratories manufacture a wide range routine and niche biochemistry reagents for use in both a research and clinical setting. With a wide measuring range, the Randox CRP assay will perform excellently to detect levels outside of the healthy range. Also available is a Full Range CRP assay particularly beneficial for use in a neonatal setting, and a High Sensitivity CRP assay, depending on your diagnostic requirements. For more information, please contact: firstname.lastname@example.org
- Shrivastava, A. K., Singh, H.V., Raizada, A. and Singh, S.K. C-reactive protein, inflammation and coronary heart disease. The Egyptian Heart Journal. 67, 89-97. (2015)
- American Heart Association. Inflammation and Heart Disease. Available from: https://goo.gl/d82Ynr (2016)
- Harvard Health Publications. What you eat can fuel or cool inflammation. Harvard Health Publications. Available from: https://goo.gl/e8m3El (2007)
- Zeyda, M. and Stulnig, T. M. Obesity, Inflammation, and Insulin Resistance – A Mini-Review. Gerontology 2009; 55:379-386 (2009)
- Mukherjeel, R. Bone and joint health are crucial aspect, usually ignored by Indians. The Times of India. Available from: https://goo.gl/qluzhI (2016)
- Anderson, G. P. COPD, asthma and C-reactive protein. European Respiratory Journal 2006; 27: 874-876. (2006)
- Hofer, N., Zacharias, E., Müller, W. and Resch, B. An update on the Use of C-Reactive Protein in Early-Onset Neonatal Sepsis: Current Insights and New Tasks. Neonatology 2012; 102: 25-36 (2012)
- Silva, P. Two Specific Proteins Allow the Exclusion of IBD in Patients with Irritable Bowel Syndrome. IBD News Today. Available from: https://goo.gl/pxMP53 (2015)