Background Gout and pseudogout are frequent causes of inflammatory joint diseases. The gold standard to diagnose these diseases is synovial fluid analysis by the use of polarized light microscopy (PLM). This technique is used in less than 10% of all gout patients referred to rheumatologists.1 Increase in the availability of synovial fluid analysis for general practioners (GPs) could improve the accuracy of the diagnoses of gout and pseudogout. Therefore synovial fluid should be able to be preserved in order to have time for transportation to and analysis with PLM.2-3
Objectives To compare three different types of synovial fluid preservation aiming to determine crystal stability in synovial fluid to assess the feasibility of preservation of synovial fluid for off-site analysis.
Methods Synovial fluid samples of 10 patients with a gout arthritis, 10 patients with a pseudogout arthritis and 10 control patients have been divided over 30 cuvets of at least 40 mcL each. 10 cuvets were stored at -20° C, 4° C and room temperature, respectively. No additives were added to the synovial fluid. All samples will be analyzed with PLM at 1, 2, 3, 4, 5, 6, 7, 8, 12 and 24 weeks. The parameters observed are the amount of crystals per view field, the size of the largest crystal, the amount of leucocytes per view field, the presence of microtophi, and the presence of intracellular crystals.
Results The preliminary results of 5 gout, 2 pseudogout and 8 control patients are analyzed at baseline, after 3 and after 6 weeks of preservation. At room temperature 40% and 60% of the monosodium urate (MSU) crystals, and 50% and 50% of the calcium pyrophosphate dihydrate (CPPD) crystals were visible after 3 and 6 weeks, respectively. At 4° C MSU crystals were identified in 60% and 40%, and in 100% and 50% of the CPPD crystals after 3 and 6 weeks, respectively. At -20° C 80% and 80% of the MSU crystals, and 100% and 50% of the CPPD crystals were seen at 3 and 6 weeks, respectively. In the control patients no crystals were detected after 3 and 6 weeks.
Conclusions A large amount of the MSU and CPPD crystals seem to be visible in synovial fluid after 3 and 6 weeks of preservation without additives at room temperature, 4° C and -20° C. This can increase the availability of synovial fluid analysis for GPs to improve the accuracy of the diagnoses of gout and pseudogout.
Owens, D., et al. (2008). A survey of the management of gout in primary care. Ir Med J 101(5): 147-9.
Galvez, J., et al. (2002). Delayed examination of synovial fluid by ordinary and polarised light microscopy to detect and identify crystals. Ann Rheum Dis 61(5): 444-7.
Kerolus, G., et al. (1989). Is it mandatory to examine synovial fluids promptly after arthrocentesis ? Arthritis Rheum 32(3): 271-8.
Disclosure of Interest None Declared