The acute phase reaction is the body's first line inflammatory defence system, functioning without specificity and memory, ahead of, and in parallel with, the adaptive immune system.

C-reactive protein (CRP) is a major acute phase protein and the serum concentration may increase more than 1000-fold in an acute phase response to an inflammatory stimulus. Axis-Shield offers an assay for CRP on both Afinion and NycoCard systems.

C-reactive protein in clinical settings
In certain countries, C-reactive protein (CRP) determination is one of the most common diagnostic  tests, both in point-of-care and in hospital settings. The requirements for CRP assays differ between clinical situations, e.g. in the physician's office and the emergency room (point-of-care-testing) vs. in-hospital ward units. In the former two settings, the availability of rapid, on-the-spot results (within 5-10 minutes) is of greater importance than having minimal imprecision or superior sensitivity in the assay. When a patient is in a ward unit, it is usually adequate for the CRP result to be available within a couple of hours. For detection of residual inflammation in patients with increased risk of cardiovascular diseases, high-sensitivity CRP assays with low imprecision are required.

In primary healthcare settings, the two major patient categories are febrile patients with suspected acute infectious diseases, and patients with chronic, often inflammatory, diseases. For both categories, evaluation of the inflammatory component of the disease process is of great importance for better and safer diagnosis and monitoring of the disease, or efficacy of treatment. Reliable, on-the-spot CRP determinations are of great importance both in diagnostic and  follow-up situations. Generally a bacterial infection will raise CRP blood levels and indicate antibiotic therapy may be required. In viral infections, CRP levels are not elevated and standard antibiotic therapy would be inappropriate.

In hospital settings, CRP is used as a diagnostic test in the emergency room, the intensive care unit, the haematology, oncology, rheumatology, paediatric, and gynaecology and obstetric departments. It is used post-operatively to support the clinical diagnosis of primary or complicating infections and also to monitor the effect of antibiotic treatment in these cases. Another important use of the CRP test is to monitor the disease progress and effect of anti-inflammatory treatment in patients with chronic inflammatory diseases, e.g. rheumatic or inflammatory bowel diseases.