CRP Test Procedure

C-reactive protein (CRP) is an acute-phase protein produced by the liver in response to inflammation, infection, and tissue damage. Discovered in 1930, CRP plays a vital role in the immune response by binding to phosphocholine on microbes, enhancing phagocytosis, and aiding in the clearance of dead cells. Elevated CRP levels are a significant marker for various inflammatory conditions, making it a crucial tool in diagnosing and monitoring disease progression.

PRINCIPLE:

It is a slide agglutination test. Latex particles coated with CRP antiserum are allowed to react with test serum. Agglutination is observed if CRP is present in a concentration of 6 mg/L or above.

REQUIREMENTS:

• Serum sample
• CRP latex reagent
• Positive and negative controls (PC; NC)
• Test card and Test Tubes
• Normal saline
• Disposable mixing sticks
• Mechanical rotator (80-100 rpm)

PROCEDURE:

1. Bring the kit reagents and sample to room temperature.
2. Place 0.05 ml of the serum into one circle of slide.
3. Place similar quantities of positive and negative controls in separate circles.
4. Gently mix the latex reagent vial (to ensure homogeneity) and place one drop to each of the circle.
5. Mix the contents of each circle evenly with disposable sticks and spread over the complete area of the circle.
6. Place the slide on mechanical rotator (80-100 rpm) for 2 minutes.
7. Examine for agglutination macroscopically.
8. Compare the results with positive and negative controls.

RESULTS:

• Agglutination indicates a positive reaction.
• If CRP test is positive, the amount of CRP will be equal to 6 mg/L or above while in case of a negative reaction (no agglutination) less than 6 mg/L.

SEMI QUANTITATIVE METHOD:

• If CRP test is positive, serial dilutions of the serum are tested.
• The highest dilution of the serum giving positive result will be the titre.

Prepare double dilutions of serum as follows.

QUALITY CONTROL:

Every test kit have Positive and Negative controls which are run parallel to all tests which are being run or perform routinely.

INTERPRETATION OF CRP TEST:

1. The increased level of CRP indicates inflammation and tissue damage.
2. The progression of an infection is also monitored
3. False negative results are seen due to prozone phenomenon.
4. It is recommended to make the final diagnosis with clinical examination and other laboratory data.

COMPARISON OF CRP AND ESR TEST:

CRP has some advantages over Erythrocyte Sedimentation Rate (ESR), though both are used as a marker of inflammation.

1. CRP is a direct measure of inflammation whereas ESR is a indirect one.
2. CRP has a more rapid response to inflammation than ESR and also returns to normal when the inflammatory condition is resolved.
3. CRP is comparatively less affected by age.
4. CRP is not raised in non-inflammatory conditions but ESR is elevated in some.

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Possible References Used

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