The Persistency and Visibility of Synovial Fluid Crystals After at Least 10 Days in Refrigerator by Light and Polarized Microscopy.

INTRODUCTION: Synovial fluid (SF) analysis is one of the most important tests used in approach to arthritis and is necessary for rheumatology fellowship training. It depends on the operator's experience and can be affected by handling, processing, temperature, type of preservative, and time from aspiration to analysis. Therefore, we aimed to reevaluate the SF with positive results for crystals, after at least 10 days for the persistency and visibility of the crystals.

METHOD: For 1 year, we reevaluated crystal positive synovial fluid samples after at least 10 days under light and polarized microscopy. The samples were sent in tubes without any preservative. After the first day of diagnosis of a crystal arthropathy, all the samples were kept in 4 °C refrigerator in a syringe without any preservative and then reevaluated.

RESULTS: 14 calcium pyrophosphate (CPP); 12 monosodium urate (MSU), 1 of which was combined CPP and MSU; and 1 post-methylprednisolone (Depomedrol) injection, steroid crystal arthropathy were found and reevaluated. In all reevaluated samples [between 10-24 (median:14 days)], the crystals were detectable again.

CONCLUSION: Our results suggests that SF CPP, MSU and methylprednisolone crystals at 4 °C without preservation could be detectable after 10-24 days (median: 14, 15.5, and 10 days, respectively) under light and polarized microscopy. It seems that the samples evaluated in emergency settings without enough time and those sent from other centers or gathering samples for trainees can be kept to detect crystals at least 10 days for all and till 22 days (for CCP and MSU) after sampling.