Synovial fluid analysis is a critical diagnostic tool in the evaluation of joint-related diseases, including infections, inflammatory conditions, and in particular crystal-induced arthropathies. The crystal arthropathies, gout and calcium pyrophosphate dihydrate deposition disease, are caused by deposition of monosodium urate monohydrate (MSUM) or calcium pyrophosphate dihydrate (CPPD) crystals, respectively. A diagnosis of urate gout or calcium pyrophosphate dihydrate deposition disease is based on characteristic clinical findings and the microscopic identification of intracellular crystals in synovial fluid, which is routinely performed in a microbiology laboratory setting. However, the accuracy and reliability of synovial fluid analysis depend heavily on the quality of the sample and the proficiency of laboratory techniques. Robust external quality assurance (EQA) programs are paramount to ensure accurate and consistent results in synovial fluid analysis.
Collection, handling, and analysis of synovial fluids can be challenging and are potential sources of variability and error. Synovial fluid samples are not as readily available as other clinical specimens, such as blood or urine. Obtaining an adequate quantity of synovial fluid samples for EQA programs can be difficult, especially considering the relatively small volume typically obtained during routine clinical procedures. Synovial fluid samples are biologically active and prone to degradation over time, particularly if not stored under appropriate conditions. Maintaining the stability of synovial fluid samples during transport and storage for EQA programs is crucial to ensure the accuracy and reliability of the proficiency testing results.
EQA programs can identify systemic method and individual laboratory issues impacting patient care and outcomes. The RCPAQAP synovial fluid program identified a wide range of sensitivities for polarised light microscopy, underscoring poor inter-laboratory reliability. Recognising the profound repercussions of an erroneous synovial fluid diagnosis, EQA programs can allow laboratories to identify areas requiring improvement, contribute to timely and accurate diagnosis, and facilitate appropriate treatment strategies, ultimately improving patient outcomes.