Test Details: ESR (Erythrocyte Sedimentation rate) test might be useful when evaluating unexplained fever, some types of arthritis and symptoms that affect muscles. Also, they can help confirm diagnosis of certain conditions, including: Giant cell arteritis, Polymyalgia rheumatica, Rheumatoid arthritis. ESR test can also help determine the severity of the inflammatory response and monitor the effect of treatment. Since an increased ESR test cannot pinpoint the problem that's causing inflammation in the body, it is usually accompanied by other blood tests, such as the C-reactive protein (CRP) test.