Refrigeration preserves synovial fluid cytology.

Abstract

Sir: We recently published an algorithm based on combinations of synovial fluid (SF) cell number thresholds and types which should considerably extend the diagnostic use of SF cytology in non-septic/crystal arthritis.' Key branch points depend on accurate values for total and differential nucleated leucocyte counts (white cell count (WCC)), ragocytes, and Reiter's cells (cytophagocytic mononuclear cells (CPMs))2; and the recognition of specific cell types for example, LE cells, tart cells. The receipt and analysis of clinical SF specimens is often delayed (60% of SFs in our laboratory are processed the same day as taken, 22% after overnight fridge storage, others arriving one or more days late). Schumacher's group reported large falls in WCC in SF kept at room temperature for a few hours, though other cytological changes were not described. 3 We investigated the effects of fridge (4°C) storage over one to three days on these key cytological indices, and the accuracy of algorithm derived diagnoses in 51 knee aspirates chosen randomly from routine diagnostic specimens, satisfying the following: (a) receipt within four hours of arthrocentesis ('fresh'); (b) possessing sufficient cells (>022xl09/1) and volume (>1-5 ml), lacking bloodstaining or clots. There were 48 'inflammatory' (25 rheumatoid, seven spondyloarthritic, eight Reiter's/reactive, and eight miscellaneous, including crystal and septic) and three osteoarthritic SFs.Fluids were examined 'fresh' and then refrigerated without dilution in the original 2 ml Li-heparin bottle. Aliquots (0-25 ml) were taken daily and processed for (a) wet preparation (ragocyte count and crystals); (b) total WCC by haemocytometer; (c) spondyloarthropathies.' A specific correct, or matching short differential diagnosis was derived in 52% of fresh fluids (58% if three crystal cases were included), falling only to 46% (52%) after two days (table 2). A further 42-46% were labelled as non-diagnostic inflammatory fluids, and only three incorrect diagnoses were made. Derived diagnoses did not change in 90% of fluids over 48 hours; four became non-diagnostic and only one incorrect. Cytological deterioration of the specimens and artefactual increases in pyknotic and 'ghost' cell numbers interfering with leucocyte counting only became a significant problem after two to three days.These results suggest that SF can be stored (and transported) under refrigerated conditions for 24 hours without significant changes in cytological indices, and for 48 hours with only minimal loss of diagnostic accuracy. This should allow wider access to regional SF cytoanalytical services, and implies that SF specimens should be promptly refrigerated if any transport or analytical delays are expected. 29-8 (7-9) 1 48 14 4 (1 9) 10.9 ( 1 7) 1.5 (0 2) 1-9 (0 4) 7-2 (2-4) 34-4 (7-2) 2 35 10-6 (1l7)* 7-2 (1-5)* 1-2 (0 2) 2 2 (0 7) 4-4 (1-4) 28-7 (7-4) 3 309 0 (1-7)t 5-5 (15)t 1.0 (02)* 2-5 (0 9) 4-5 (1-6)

Preanalytical Considerations for Joint Fluid Evaluation

“…Therefore, it is recommended that samples being sent to laboratories be packaged with cold packs and shipped overnight to maintain sample value. 32 When providing direct smears, ensure that these slides are completely dry before packaging and kept away from exposure to formalin fumes. Do not refrigerate slides, as subsequent condensation may result in cell lysis.…”