CRP (C-reactive Protein)
- The CRP test determines the amount of C-reactive Protein in a blood sample. The liver produces a protein known as C-reactive Protein.
- CRP is generally found in low amounts in the blood. if there is inflammation in the body, the liver will release more cortisol into the bloodstream. Elevated CRP levels could indicate a significant inflammatory medical disorder.
- It is also known as Pentraxin-1. It is a major component of acute-phase protein (APP). Here C stands for carbohydrate which binds on the capsule of pneumococci.
- It was discovered by Tillet and Francis in 1930 S.
Normal level: <06 Mg/dl
High-sensitivity CRP (hs-CRP) measurements may be used as an independent risk marker for the identification of individuals at risk for future cardiovascular disease.
Increased CRP (C-reactive Protein) level:
- A high or increasing amount of CRP in the blood suggests the presence of inflammation, but will not identify its location or the cause.
- Suspected bacterial infection- A high CRP level can confirm that you have a serious bacterial infection.
Normal High value:
- Bacterial infection
- Viral infection
Very High value:
- Blood cancer- Lymphoma
- Multiple myeloma
Increase CRP (C-reactive Protein) in children:
- Pneumonia
- Viral infection
- Cough and cold
- Fever
- Liver infection
- Inflammation
- sepsis
CRP Increase in these conditions:
- Increase the risk of heart attack
- Chronic infection
- Inflammatory condition
- Bacterial Infection
Methods of detection CRP (C-reactive Protein)
The CRP (C-reactive Protein) test can be done by three methods:
- Qualitative method
- Semi-quantitative method
- Quantitative method
1. Qualitative method
This type of test tells us only the presence or absence of CRP in the blood. This test is performed on the slide.
Principle
When a patient’s serum mixes with CRP latex reagents, if in serum CRP is present, then it reacts with latex particles and produces agglutination. If not present, then do not show agglutination.
Reagents:
- Latex reagent
- Positive control
- Negative control
Apparatus:
- Slide
- Pipettes
- Sticks
- Stopwatch
Sample:
- Patient serum
Procedure
- Bring all reagents and serum samples to Room Temperature and mix latex reagent gently before use.
- Take the CRP kit, the kit contains 3 vials. 1 vial has CRP latex reagent, 2nd vial positive control, and 3rd negative control.
- Place one drop of positive control on one circle of a black glass slide.
- Place one drop of negative control on the separate circle of the slide.
- Take the patient serum and place one drop or 40 microliters on a separate circle of slide.
- Now add one drop of CRP latex reagent to each of the circles.
- Mix the reagent using the mixing stick provided in the kit.
- Make sure it is not to mix two separate circles with one stick.
- Starts the stopwatch for two minutes and shake the slide gently.
- Observe the slide for agglutination
Result
If agglutination is seen in the slide then the test is positive, if there is no agglutination is seen in the slide then the test is negative.
2. Semi-quantitative method
If the qualitative CRP test is positive, serial dilution of the serum is tested. The highest dilution of serum going positive then the result will be titer.
Requirements:
- Test tubes
- Saline
- Reagent
- Serum
Procedure
1. As shown in the following table, prepare a physiological saline 0.9% dilution of the specimen.
Dilution | CRP (ug/ml) in undiluted sample |
1:2 | 14 |
1:4 | 28 |
1:8 | 56 |
1:16 | 112 |
1:32 | 224 |
1:64 | 448 |
2. Then proceed for each dilution in the same manner as the qualitative test.
Result
Positive: Agglutination of latex particles, a symptom that measurable and large amounts of C-reactive protein are present.
Negative: No Agglutination.
The serum’s CRP titre for Semi-Quantitative Test Results is determined by the last serum dilution at which agglutination is visible.
Calculation of Titre
The CRP ug/ml is equal to 7 times D, where D is the greatest serum dilution showing agglutination and 7 is the ug/ml sensitivity.
3. Quantitative method
This type of CRP test tells us the exact value of CRP in the blood. This test is performed in the biochemistry analyzer or turbidimeter
Principle
The latex particles coated with anti-CRP are agglutinated when they react with a sample that contains C-reactive protein. The latex particles are proportional to the concentration of the CRP in the sample and can be Measured by turbidimetry.
Reagent
- Diluent (R1)—Tris buffer, sodium azide
- Latex reagent (R2) – Latex particles coated with goat anti-human CRP, sodium azide. Mix gently before use.
- Mix gently before use.
- CRP calibrator- Human serum.
Apparatus:
- Semi-auto analyser
- Pipette
- Tubes
Sample:
- Patient serum
Procedure
- Warm the working reagent at 37*C.
- Using distilled water zero the instrument.
- Take 450 ul. of diluent in a test tube.
- Add 50 ul. of latex reagent.
- Add 5 ul. of serum.
- Mix well, and apply in the instrument.
- Observe the readings and note them down in logs.
Limitations of CRP (C-reactive Protein)Test
- The CRP concentration is not correlated with the agglutination reaction’s strength. With marginally elevated or noticeably elevated concentrations, weak responses can happen.
- False negatives may be caused by an overabundance of antigens, a prozone phenomenon. Therefore, it is advised to retest at a 1:10 dilution for all negative sera.
- Due to a drying effect, reaction times greater than those stated may result in apparent false reactions.
- Sera that are polluted or highly lipemic can result in false positive results.
- For this test, just serum should be utilized.
- For positive specimens, a quantitative titration method is necessary to see rising or falling proportions.
- Positive results may be obtained from patients with high titres of rheumatoid factors.
References
- Lab Tests Online- C-Reactive Protein.
- Mayo Clinic- Tests and Procedures- C-reactive protein test.
- MedlinePlus- C-reactive protein.
- MedicineNet- C-Reactive Protein (CRP).
- Healthline- C-Reactive Protein Test.
- The New York Times, Health Guide- C-Reactive Protein.
- mountsinai.org/health-library/tests/c-reactive-protein
- Microbiology Info.com. C-Reactive Protein (CRP) Test- Principle, Uses, Procedure
- Microbe online.com, C-reactive protein (CRP) Test: Principle, Procedure, Result
- Wikipedia, C-reactive protein