C-reactive protein (CRP) by nephelometry (plasma)

Why Is This Test Done?

Your healthcare provider may order a CRP test to check for signs of inflammation. This can help diagnose conditions like infections (such as pneumonia or urinary tract infections), monitor chronic diseases (like rheumatoid arthritis or lupus), or evaluate how well a treatment is working. It may also be used before or after surgery to assess risk for complications.

What Does a High or Low CRP Level Mean?

A high CRP level often indicates inflammation or infection. While not specific to one condition, elevated CRP can signal areas where your body is responding to injury, illness, or an overactive immune response. A low CRP level usually means there is little to no inflammation present.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The blood is then processed to separate plasma, which is sent to a lab for analysis using nephelometry, a method that measures how much light a protein scatters.

What Are Common Causes of Abnormal Results?

Elevated CRP levels can be caused by infections (bacterial, viral, or fungal), autoimmune diseases (like rheumatoid arthritis or lupus), injuries, surgeries, or other inflammatory conditions. Low CRP levels may occur in people with very mild inflammation or those who are generally healthy without active inflammatory conditions.