Ace It with Style! 2026 Clinical Lab Wiz: Urinalysis & Body Fluids Practice Test Extravaganza!

In synovial fluid analysis, distinguishing crystals by their shape and how they interact with polarized light is key. Pseudogout is caused by calcium pyrophosphate dihydrate crystals, and the hallmark appearance is rhomboid-shaped crystals that are positively birefringent. Positive birefringence means these crystals shift to a blue color when aligned with the light’s slow axis, which helps tell them apart from other crystals. This combination—CPPD composition, rhomboid shape, and positive birefringence—is classic for pseudogout.

For context, gout crystals are monosodium urate: needle-shaped and negatively birefringent (yellow when parallel to the slow axis). Cholesterol crystals are plate-like and non-birefringent.