The diagnosis of rheumatoid arthritis (RA) mainly depends on the presence of signs and symptoms. However, there is a wide range and degree of severity of these signs and symptoms. In addition, there are several inflammatory and arthritic conditions that manifest with similar symptoms. This makes diagnosis difficult.
Steps in diagnosis of Rheumatoid arthritis include the following:
Detailed history of the onset and severity of the symptoms as well as family history of rheumatoid arthritis or other autoimmune disorders is obtained. The physician enquires about swollen and painful joints.
A detailed physical examination is carried out. This includes checking the affected and other joints for swelling, pain and signs of inflammation. Standard examination includes assessment of swollen and tender joints in 66 to 68 places including hands, upper limbs, knees and feet.
Health assessment questionnaires
There are several patient based questionnaires and measures called health assessment questionnaires (HAQ) that measure patient disability and quality of life. In addition these questionnaires also measure the patient’s own perception of the disease burden.
There are no tests that can definitely pin point rheumatoid arthritis. However, these tests may help differentiate this condition from other diseases and disorders that affect the joint functioning. Routinely several blood tests are ordered. These include:-
Erythrocyte sedimentation rate (ESR) – this is a routine blood test that is not definitive of rheumatoid arthritis. A sample of blood is allowed to stand in a tube. If the cells in blood sink to the bottom faster making a larger column of cells after 1 and 2 hours the ESR is said to be raised. Rheumatoid arthritis is a condition in which ESR is raised.
Full blood count – this is another routine blood test. It can detect anemia or shortage of red blood cells and raised white blood cells. Raised WBCs may be indicative of an inflammatory condition.
C-reactive protein (CRP) – this is a blood test that is a marker for inflammation. Raised CRP is not a definitive indicator of rheumatoid arthritis but is a marker of presence of inflammation anywhere in the body.
Rheumatoid factor – this is a relatively specific test for rheumatoid arthritis. There is presence of this indicative factor in nearly 80% of all persons with rheumatoid arthritis. Presence of rheumatoid factor may not be detected in early stages of the disease. In addition around 1 in 20 healthy persons may test positive for rheumatoid factor. Thus presence of rheumatoid factor is not absolutely indicative of rheumatoid arthritis.
Several imaging studies that look at the joints that are affected may help in diagnosis of rheumatoid arthritis. The most commonly employed imaging study is an X ray of the joints. Presence of two or more eroded and destroyed joints is significant of rheumatoid arthritis. A joint ultrasonography is also advised to check for decreased space within the bones of the joint and damage to the cartilage and soft tissues. An MRI scan or Magnetic resonance imaging scan of the joint can also provide detailed information about the joint damage due to rheumatoid arthritis.
Combination of patient based scores and disability assessment by physician
The disease activity score 28 (DAS28) combines 28 swollen and 28 tender joints (hands, arms, and knees) and patient’s own perception of the disability. It also includes blood tests like erythrocyte sedimentation rate. DAS28 has a complicated mathematical assessment and now a simplified version is used that combines 28 tender and swollen joint counts, doctors’ and patients’ assessments, and C-reactive protein levels.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)