Assessment of RA
Assessing Disease Activity Disability Radiography Musculoskeletal Ultrasound Magnetic Resonance Imaging Imaging in the Diagnosis and Management of RA Prognostic Features of RA Assessing Disease Activity A composite disease activity score should be performed at every visit. This score includes the number of tender and swollen joints (using 28 joint counts); global assessment of disease activity fr
Imaging in the Diagnosis and Management of RA
Assessing Disease Activity
A composite disease activity score should be performed at every visit. This score includes the number of tender and swollen joints (using 28 joint counts); global assessment of disease activity from the patient (‘How has your arthritis been over the last week?’), scoring between 0 (very well) and 10 (very poor); and global assessment of disease activity by the physician, scoring between 0 (very well) and 10 (very poor), with or without a serum acute-phase reactant (Table 3). Disease activity can be classified into states of remission or low, moderate or high disease activity.[13] The three validated scores currently in use in South Africa (SA) are the Clinical Disease Activity Index (CDAI), the Simplified Disease Activity Index (SDAI) and the 28-joint Disease Activity Score (DAS-28).[14-16] The CDAI is the easiest measurement to perform, and the final score ranges from 0 to 76 (higher scores indicate higher disease activity).[16]
Disability
Physical disability can be measured with the Health Assessment Questionnaire-Disability Index (HAQ-DI).[17] This self-administered questionnaire should ideally be completed 6 - 12-monthly, and with motivation/remotivation for biologic therapy, work assessment and disability boarding.
Radiography
Baseline hand and feet radiographs should be performed for diagnostic (marginal erosions, joint space narrowing and juxtaarticular osteopenia) and prognostic purposes. These images are not sensitive enough to detect changes early in the disease, but are readily available, reliable and low in cost. A chest radiograph is appropriate to exclude rheumatoid lung disease or tuberculosis (TB) prior to commencing therapy.
| Table 3. Disease activity formulas and categories | |||
| Index | Formula | Remission | Low/Moderate/High Disease Activity |
| CDAI | TJC + SJC + PGA (cm) + MDGA (cm) | ≤2.8 | Low: ≤10, Moderate: ≤22, High: >22 |
| SDAI | TJC + SJC +PGA (cm) + MDGA (cm) + CRP mg/dL | ≤3.3 | Low: ≤11, Moderate: ≤26, High: >26 |
| DAS-28 | 0.56*√(TJC) + 0.28*√(SJC) + 0.7*ln (ESR) + 0.014*PGA (cm) | ≤2.6 | Low: ≤3.2, Moderate: ≤5.1, High: >5.1 |
| CDAI = Clinical Disease Activity Index; TJC = tender joint count; SJC = swollen joint count; PGA = patient global assessment; MDGA = physician global assessment (0 = very good; 10 = very poor); SDAI = Simplified Disease Activity Index; CRP = C-reactive protein; DAS-28 = Disease Activity Score; ESR = erythrocyte sedimentation rate. | |||
Musculoskeletal Ultrasound
High-resolution musculoskeletal ultrasound (MSUS) is safe and relatively inexpensive, and allows accurate assessment of soft-tissue inflammation and joint erosions, and placement of intra-articular injections that is superior to clinical examination.[16,18] A trained and experienced rheumatologist or MSUS technician is required.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI), particularly contrast-enhanced MRI, is highly sensitive, demonstrating synovitis and tenosynovitis, and can detect erosions up to 3 years before they are evident on conventional radiographs. Bone marrow oedema may be seen on MRI in early RA, and is a strong predictor of bone damage.[19] Limited access to MRI scans together with cost limit the availability of this modality.
Imaging in the Diagnosis and Management of RA
While MSUS-detected tenosynovial hypertrophy with Doppler signal and MRI-detected tenosynovitis at the metatarsophalangeal joints are very specific for RA, recent studies have found that MRI and MSUS did not add value to the diagnosis of RA compared with the 2010 ACR/EULAR classification criteria. MSUS is useful when there is diagnostic doubt.[20] At present, MSUS and MRI scans are not part of routine diagnosis and should be used to visualise soft-tissue and bone lesions of a problem joint, or to confirm or exclude synovitis where there is clinical uncertainty.
Regular routine imaging of RA joints is not necessary: there is no evidence that follow-up assessments with either MSUS or MRI lead to better outcomes than clinical assessments, and they have the potential to lead to over-treatment.[21,22]
Prognostic Features of RA
Poor prognostic factors include seropositivity, i.e. high titres of rheumatoid factor or anti-cyclic citrullinated peptide antibody; high inflammatory markers; erosions on radiographs within the first 2 years of disease; functional disability; extra-articular disease; cigarette smoking; and delayed diagnosis.[23]
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Tarr, G., Govind, N., Seboka, M., Gardiner, E., & Hodkinson, B. (2024). South African Rheumatism and Arthritis Association 2024 updated guidelines for the management of rheumatoid arthritis. South African Medical Journal, 114(9), e2598.