What is the diagnostic workup for inflammatory arthritis?

From the Guidelines

The workup for inflammatory arthritis should begin with a thorough history and physical examination, focusing on joint symptoms, pattern of involvement, duration, and associated systemic features, and patients presenting with arthritis should be referred to, and seen by, a rheumatologist within 6 weeks after the onset of symptoms, as recommended by the 2016 update of the EULAR recommendations for the management of early arthritis 1. The initial evaluation should include laboratory testing such as complete blood count, comprehensive metabolic panel, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) to assess inflammation.

• Specific serologic tests include rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, antinuclear antibodies (ANA), and HLA-B27 testing depending on clinical suspicion, as suggested by the EULAR recommendations 1.
• Synovial fluid analysis is crucial when joint effusion is present, examining for cell count, crystal analysis, culture, and glucose levels.
• Imaging studies should start with plain radiographs of affected joints to assess for erosions, joint space narrowing, or other changes, and more advanced imaging like ultrasound can detect early synovitis, while MRI may reveal bone marrow edema and early erosions not visible on radiographs, as recommended by the EULAR recommendations for the use of imaging of the joints in the clinical management of rheumatoid arthritis 1. The goal of this comprehensive approach is to differentiate between various types of inflammatory arthritis, such as rheumatoid arthritis, psoriatic arthritis, reactive arthritis, and spondyloarthropathies, and to allow for timely initiation of appropriate treatment to prevent joint damage and disability, as emphasized by the management of immune-related adverse events in patients treated with immune checkpoint inhibitor therapy: ASCO guideline update 1. A definite diagnosis in a patient with early arthritis should only be made after a careful history taking and clinical examination, which should also guide laboratory testing and additional procedures, as stated in the 2016 update of the EULAR recommendations for the management of early arthritis 1.

From the Research

Workup for Inflammatory Arthritis

The workup for inflammatory arthritis involves a combination of clinical evaluation, laboratory tests, and imaging studies.

• The diagnosis of rheumatoid arthritis (RA) should be considered if there is at least one joint with definite swelling that is not better explained by another disease 2, 3.
• Laboratory tests that support a diagnosis of RA include:
  • Rheumatoid factor (RF)
  • Anti-citrullinated protein antibody (anti-CCP)
  • Elevated C-reactive protein (CRP) level
  • Elevated erythrocyte sedimentation rate (ESR) 2, 3, 4
• The sensitivity, specificity, and accuracy of these tests vary, with anti-CCP being more specific than RF for the diagnosis of RA 4.
• Combined detection of RF, anti-CCP, CRP, and ESR is beneficial for confirming a diagnosis of RA 4.
• Other laboratory tests that may be useful in the workup of inflammatory arthritis include:
  • Complete blood count (CBC) with differential
  • Assessment of renal and hepatic function
  • Testing for hepatitis B, hepatitis C, and tuberculosis in patients taking biologic agents 3
• Imaging studies, such as plain X-ray of the hands and feet, may also be useful in assessing joint damage and disease severity 5.
• Serum 14-3-3η level has been identified as a valuable marker for the diagnosis of RA and may have prognostic value 5.

Laboratory Tests

Laboratory tests play a crucial role in the diagnosis and management of inflammatory arthritis.

• ESR and CRP are widely used laboratory markers of systemic inflammation, but they lack sensitivity and specificity and should be used in combination with clinical history and physical exam for diagnosis and monitoring of pathological conditions 6.
• Discordance between ESR and CRP measurements can occur, and proper utilization of these tests requires consideration of various physiological factors that can affect measurements 6.

Clinical Evaluation

Clinical evaluation is essential in the workup of inflammatory arthritis.

• A thorough medical history and physical examination can help identify symptoms and signs of inflammatory arthritis, such as joint swelling, pain, and stiffness.
• The clinical evaluation should also include an assessment of disease severity and impact on daily activities.