Crystal arthropathy - microscopy findings (CPPD vs urate vs cholesterol)
Core concept
- Compensated polarised light microscopy - a first-order red compensator is inserted with its slow axis marked on the stage
- Birefringence sign = the colour when the crystal's long axis lies PARALLEL to the compensator axis
- Negative -> yellow when parallel (blue when perpendicular)
- Positive -> blue when parallel (yellow when perpendicular)
- "ABC" mnemonic - Aligned Blue = Calcium (CPPD)
- The converse: aligned yellow = urate
3 more sections, plus exam facts
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