The main biologic sign of inflammation is an increase in the erythrocyte sedimentation rate (ESR). In addition an increase in plasma concentrations of a group of proteins known as acute-phase proteins is a good indicator of local inflammatory activities and tissue damage. The acute phase proteins include C-reactive protein (CRP), inflammatory mediators (e.g. complement components c3 and c4, fibrinogen, etc.
CRP is prominent among the acute-phase proteins because it provides fast and adequate information of the actual clinical situation; as a result CRP is a direct and quantitative measure of the acute-phase reactions.
Measures of CRP add to the diagnostic procedure in selected cases (e-g. in the differentiation between a bacterial and a viral infection). An extremely elevated CRP is suggestive of a possible bacterial infection. The CRP level may be useful also for monitoring the effect of treatment and for early detection of postoperative complications or intercurrent infections. The CRP is a parameter for inflammatory activity.
CRP is a method of choice for screening for inflammatory and malignant diseases and monitoring therapy in inflammatory disease. Elevations of CRP occur in nearly to diseases states, including bacterial infection, viral infections, and myocardial infraction specificity rules out CRP as a definitive diagnostic tool.
The CRP test has been widely used to detect infection in circumstances where microbial diagnosis is difficult. These conditions include septicemia and meningitis in neonates, infections in immunosuppressed patients, serious post-operative infections etc.
CRP levels rise following the tissue injury or surgery. In uncomplicated cases the level of CRP peaks about 2 days postoperatively and gradually returns to normal levels within 7 to 10 days. CRP is synthesized more rapidly than other acute phase proteins; assays of CRP are the measurement of choice in suspected inflammatory conditions.
Rapid latex agglutination test
Principle: The test is based on the reaction between patient serum containing CRP as the antigen and the corresponding antibody coated to the treated surface of latex particle. The coated particles enhance the detection of an agglutinate reaction when antigen is present in the serum being tested.
Reagent and materials required
• CRP latex reagent
• Glycine – saline buffer
• Capillary pipette
• Applicator sticks
• Glass slide
• Serologic pipettes and rubber bulb
Include positive and negative control serum.
1. Deliver one drop of undiluted serum on a slide by using capillary Pipette.
2. Deliver one drop of positive and negative control on separate (other) circle of the slide
3. Add one drop of CRP latex reagent to each serum specimen and to each control
4. Mix the suspension using separate applicator sticks.
5. Tilt the slide back and forth slowly for two minutes observe for agglutination macroscopically.
Positive reaction – agglutination Negative reaction– absence of agglutination