Rheumatological Investigation Autoantibodies Imaging Synovial Fluid

The answer first

The rheumatological investigation panel integrates autoantibody testing, imaging (ultrasound, MRI, conventional radiography), and synovial fluid analysis to characterise inflammatory, crystal, infective, and degenerative joint disease. The FRACP candidate must defend three skills: (1) the antinuclear antibody (ANA) pattern and titre interpretation (a positive ANA at low titre in low-prevalence populations is more likely false-positive than true-positive); (2) the anti-cyclic citrullinated peptide (anti-CCP) antibody as the high-specificity test for rheumatoid arthritis (sensitivity 70 per cent, specificity 95 per cent — far superior to rheumatoid factor); and (3) the synovial fluid cell count and crystal analysis as the discriminator between septic arthritis, gout, CPPD, and inflammatory arthritis. The answer-first synthesis is: take a structured history and examination; perform targeted autoimmune serology (ANA first; extractable nuclear antigens and disease-specific antibodies if ANA positive); use imaging appropriate to the question (X-ray for structural change, ultrasound for synovitis and crystals, MRI for early inflammation and soft tissue); aspirate any undiagnosed effusion for cell count, crystals, Gram stain, and culture. ^{[1] [4]}

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