Development and evaluation of a method for preservation of synovial fluid wet preparations for quality control testing of crystal identification.

We describe a technique for embedding drops of fresh synovial fluid in mounting resin to prepare test slides that retain crystal morphology for at least 2 weeks. Hospital and private rheumatologists were solicited nationwide to test themselves and their staff with 5 unknown specimens. Eighty-nine percent identified monosodium urate (MSU) crystals from a tophus but only 71% identified smaller and less frequent MSU. Seventy-five percent correctly identified calcium pyrophosphate dehydrate and 42% detected steroid crystals. Apatite crystal clumps included as control slides with no birefringent material were suspected by only 7%. This or another method which simulates actual practice by also testing the equipment and handling of the microscope is proposed as an important component of quality control testing programs for synovianalysis.