An analysis of 10 years of synovial fluid crystal external quality assurance data

Definitive diagnosis of gout relies on the identification of monosodium urate (MSU) crystals in synovial fluid. This process has confounders, including differentiating different crystal types, which require a high level of skill and relevant equipment. The Royal College of Pathologists of Australasia Quality Assurance Programs has provided a synovial fluid crystal identification external quality assurance (EQA) program for 15 years. In this article, we describe and analyse the current and past performance of this program. The key findings are that synovial fluid crystal identification has been and remains suboptimal in a significant proportion of the program's laboratories. There are consistently poorly performing laboratories, and there is a general issue with differentiating between MSU and calcium pyrophosphate crystals. The identification of MSU crystals provides definitive diagnosis of gout, leading to a lifetime treatment. Therefore, this represents an area of laboratory practice where more training is required to reduce patient risk.