Send joint fluid for fluid analysis, including:
- Cell count and differential,
- Gram stain,
- Culture and sensitivity, and
- Microscopic analysis for crystals. If crystals are found, their shape and appearance under polarized light are diagnostic.
In gout, crystals of monosodium urate (MSU) appear as needle-shaped intracellular and extracellular crystals. Negatively birefringent urate crystals are seen under a polarizing light.
In pseudogout, we see calcium pyrophosphate (CPP) crystals, which appear shorter than MSU crystals and are often rhomboidal.
Related Condition: Olecranon Bursitis.
https://emedicine.medscape.com/article/329958-workup