Blood Tests to Diagnose ArthritisWebMD describes the different blood tests used to diagnose arthritis and other inflammatory diseases.Rheumatoid Factor (RF) Blood Test Results and Significance on ...Read about the rheumatoid factor (RF) blood test used for the diagnosis of rheumatoid arthritis, lupus and sarcoidosis. Elevated results, or high levels, indicate ...Blood Test May Predict Rheumatoid ArthritisA new blood test may detect early rheumatoid arthritis before symptoms develop, says a study in Arthritis & Rheumatism.