C - reactive protein

C - reactive protein ( CRP ) ◌ C-reactive protein was originally discovered as a substance in the serum of patients with acute inflammation that react with the C polysaccharide of pneumococcus, this protein which cause the reaction is called CRP. ◌ It is an acute phase protein which act as a non specific inflammatory indicator.

Characteristics of CRP ◌ CRP is alpha-globulin produced in liver. ◌ CRP is acute phase protein that appears in sera of individuals in response to inflammatory conditions (e.g. rheumatoid arthritis and lupus …,etc.) and some forms of cancer. ◌ Increase within 4-6 hours following infection, surgery or trauma. ◌ CRP also elevated due to inflammation in the arteries of the heart and is a marker for coronary artery disease called high sensitive CRP(hs- CRP).

◌ CRP is not specific. A high result serves as a general indication of acute inflammation but can’t show where the inflammation is located or what is causing it so, Other tests are needed to find the cause and location of the inflammation. ◌ It is thermolabile destroyed by heating at 70◦ C for 30 min. ◌ Don’t cross human placenta. ◌ Act as opsonin to help in complement activation and has a receptor on phagocytic cells.

CRP pathophysiology

Why it is done? ◌ Identify and keep track of infections and diseases that cause inflammation. ◌ Check for infection after surgery. CRP level normally rise within 4-6 hr of surgery and then go down by the third day after surgery. If CRP level stay elevated after 3 days of surgery, an infection may be present. ◌ Check to see how well treatment is working, such as treatment for cancer or an infection. CRP level rise rapidly with infection but quickly become normal if you are responding to treatment.

CRP vs ESR ◌ Both are indicators for non specific inflammation, but CRP is a more sensitive and accurate reflection of the acute phase response than the ESR, since ESR may be normal while CRP is elevated ◌ But.. CRP appears and disappears more quickly than changes in ESR. Therefore, your CRP level may drop to normal following successful treatment, whereas ESR remain elevated for a longer period. Days post stimulation

Conditions in which CRP is normal whereas ESR is increased : 1.Pregnancy due to increase in fibrinogen. 2.Nephrosis in which hypoalbuminemia present but fibrinogen and globulins increased. 3.Anemia. 4.Hypoalbuminemia. 5.Drugs.

Normal value: 0.6 mg/dl or 6 mg/L. CRP Test :- 1.1 drop of reagent is mixed with 50ul of sample. 1.If positive: serial dilution is done to detect the titer. 2. If negative: serial dilution is done to exclude probability of very high concentration of CRP “prozone effect” 2.Titer is detected by multiplying dilution factor by 0.6 mg/dl or 6 mg/L.

50ul sample 50ul 1:2 1:41: Titer (mg/L) = NS Add 132 Total Dilution agglutination And so on;