Investigations
1st investigations to order
rheumatoid factor (RF)
Test
One of the autoantibodies frequently seen in patients with rheumatoid arthritis (RA) but can also be seen in hepatitis C, chronic infections, and other rheumatological conditions. Approximately 30% of RA patients are RF negative.[51] Very high values (i.e., >100 IU) are more specific for RA. However, values >1000 IU are not common and should prompt consideration of other conditions, such as hepatitis C and cryoglobulinaemia, as the cause.
Result
positive (60% to 70% of patients)
anti-cyclic citrullinated peptide (anti-CCP) antibody
radiographs
Test
Erosions start at the margins of the joint, affecting the subchondral bone first, and progress to cause joint space narrowing. Radiographs are done at baseline and then repeated as needed if clinically indicated. Erosions are seldom useful for treatment decisions because they are seen in late disease; most of the benefit of treatment of rheumatoid arthritis is seen when treatment is started before erosions develop. Erosions signify a worse prognosis.
Result
erosions
ultrasonography
Test
May complement x-ray in the evaluation of suspected rheumatoid arthritis (RA); it may detect synovitis of the wrist and fingers at the initial presentation.[57][58]
The presence of erosions, synovial hypertrophy, and hyperaemia on ultrasound increases the post-test probability of inflammatory arthritis in seronegative patients.[60]
Ultrasound provides prognostic information linked to progression (e.g., detecting synovitis).[56] It may be a useful monitoring tool when clinical examination is inconclusive or is inconsistent with other signs of disease activity.[72]
UK guidelines do not currently recommend ultrasound for routine monitoring of disease activity in adults with RA.[62]
Result
synovitis of the wrist and fingers
Investigations to consider
disease activity score(s)
Test
Determining disease activity and presence of poor prognostic factors at diagnosis (functional limitation, extra-articular disease, positive rheumatoid factor [RF], positive anti-cyclic citrullinated peptide [anti-CCP], bony erosions on radiograph) helps to inform initial treatment decisions.
Composite disease measures are derived from the American College of Rheumatology (ACR) core data set, which includes: tender joint count; swollen joint count; functional status measured by a health assessment questionnaire (HAQ); multidimensional HAQ (MDHAQ) or its derivatives; pain; patient and physician global assessment of disease activity; and either an erythrocyte sedimentation rate (ESR) or CRP as a marker of inflammation.
Any three or more of these combined into a composite index can be used for disease activity monitoring. The most commonly used measures are the disease activity score (DAS), the 28-joint count version of DAS (DAS28), the simplified disease activity index (SDAI), the clinical disease activity index (CDAI), and routine assessment patient index data (RAPID3), all of which are recommended by the ACR.[63][64][65][66]
Each disease activity measure has its own thresholds of disease activity. For consistency the same disease activity measure should be used throughout the patient's management. Studies have shown that with close monitoring of disease activity and treating to a target value, it is possible to achieve good responses with any DMARD or combination with biological agents.[67][68][69]
Result
affirmative
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