The diagnostic standard is synovial fluid or tophus aspiration with identification of monosodium urate crystals.
Monosodium urate crystals showing negative birefringence[1]Synovial fluid is aspirated from the inflamed joint by careful arthrocentesis.
The sample is then analyzed for characteristic negatively birefringent monosodium urate crystals which appear needle-like structures of 1–20 μm in length under polarized microscopy. This is central to confirm the diagnosis of gout. 22303530 18299687
It also helps in differentiating gout from acute calcium pyrophosphate crystal arthritis (pseudogout) and septic arthritis.16707533
