Septic arthritis — SCE Rheumatology MCQ
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Correct answer: C — Synovial fluid Gram stain, culture and crystal analysis
Synovial fluid Gram stain, culture and crystal analysis is the single best answer because organisms in neutrophil-predominant synovial fluid diagnose septic arthritis. The stem is testing investigation selection, not isolated recall, so the relevant clinical pattern and risk context determine the answer. Synovial fluid microscopy, Gram stain and culture is less suitable because it fits a different clinical pattern or a different treatment threshold; MRI of the sacroiliac joints, High-resolution CT chest and Renal biopsy do not address the key discriminator in this vignette. Clinical pearl: in SCE-style rheumatology questions, autoantibodies, imaging and synovial fluid findings should be interpreted with the whole phenotype.
Reference: BSR hot swollen joint guidance; EULAR imaging/autoantibody recommendations