Laboratory Measures. Blood tests are frequently used in the management of RA. Patients often undergo regular blood tests as part of DMARD monitoring but they can also be used to monitor disease activity as well as help with diagnosis and prognosis. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are commonly used to monitor disease activity as valid indicators of inflammation. Their main drawback is that they are not specific for RA inflammation and therefore can be influenced by concomitant infection or inflammation from a different source. Currently there is no specific test to monitor disease activity in RA. Other blood tests that reflect disease activity in RA include a rise in other acute phase proteins such as alkaline phosphatase (this is an important fact to remember as some non specialists may mistake a rise in alkaline phosphatase as a side effect of drug treatment), ferritin, platelets and immunoglobulins. Conversely active disease in RA can be associated with a reduction in haemoglobin and albumin. A persistently raised acute phase protein in RA is an important observation to make as there is good evidence that these patients have a worse prognosis. There is good correlation between raised ESR and CRP with clinical measures, although this is predominantly with swollen joint counts rather than tender joint counts [Xxxxxxxx et al. 1987; xxx Xxxxxxx et al. 1994]. Continued elevation of ESR and CRP are also associated with more rapid radiological progression compared to those RA patients with a normal ESR and CRP. This increased radiological progression has been shown in both early disease [xxx Xxxxxxx et al. 1994] as well as more longstanding disease [Hassell et al. 1993]. Although in general acute phase proteins provide a good marker of disease activity in RA, some patients may only have small joint involvement which may not mount a large enough inflammatory response to be detected and in a small number of patients despite evidence of widespread synovitis clinically, there is no significant rise in acute phase proteins. Blood tests useful in the diagnosis and prognosis of RA include rheumatoid factor and the more recently described anti-cyclic citrullinated peptide (anti-CCP) antibodies. Rheumatoid factor is an immunoglobulin directed against the Fc portion of IgG. It is reported as being positive in about 70-80% of RA patients although negative results do not rule out disease. [Xxxxx et al. 1991] Rheumatoid factor may be seen in other rheumatologic...
