Delayed examination of synovial fluid by ordinary and polarised light microscopy to detect and identify crystals

Abstract

Objective: To determine the reliability of a delay in the microscopic examination of synovial fluid (SF) to detect and identify crystals. Methods: Ninety one SF samples were examined, 31 with monosodium urate (MSU) crystals, 30 with crystals of calcium pyrophosphate dihydrate (CPPD), and 30 containing no crystals. The specimens were stored with EDTA, sodium heparin, and without anticoagulant at 4ºC before examination at 24 and 72 hours with ordinary and polarised light microscopy. Another aliquot of the same samples was stored in a plastic container without anticoagulant at −80°C and examined after two months. Results: When the samples stored at 4ºC were re-examined after 24 hours, intracellular crystals of MSU were seen in 90/93 (97%) cases where they had been identified previously and 89/93 (96%) cases after 72 hours. Similarly, CPPD crystals were identified in 90/90 (100%) and 87/90 (97%) cases after 24 and 72 hours. Examination of the samples stored at −80°C showed intracellular MSU crystals in 25/31 (81%) of cases and CPPD crystals in 25/30 (83%). No crystals were seen in any sample which had previously been diagnosed as crystal-free. Conclusions: Deferred microscopic examination of refrigerated or deep frozen SF provides a strong probability of detecting MSU or CPPD crystals if these are present initially.

The added value of synovial fluid centrifugation for monosodium urate and calcium pyrophosphate crystal detection

“…Another study highlighted the high sensitivity and specificity of stained cytospin preparations for CPP crystal detection [9]. Repeated examination of the same SF 24 h after arthrocenthesis was also useful to increase the yield of crystal identification [13,14].…”

“…Both tubes, filled with 1 ml of SF, were stored in a refrigerator at 4°C awaiting microscopy [6,[12][13][14][15][16][17]. SF smears were microscopically examined before and after centrifugation, as soon as possible, within 5 days as target:…”

Is it easy to clinically distinguish inflammatory arthritis of bacterial origin from monoarthritis attacks of gout disease?

“…It should be kept in mind that crystals formation and resolution depend on the pH and temperature; after aspiration the fluid should be examined rapidly at room temperature. [16] Cytospin and Diff-Quick (Dade Behring-Switzerland) stain technique has high sensitivity and specificity.…”

Dried cytospin preparations of synovial fluid are a stable material for long-time storage and delayed crystal analysis

“…Several studies assessed the impact of storage conditions and duration on the number and morphology of monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals [1,[3][4][5]. Crystals can be maintained for prolonged periods without morphological changes by freezing [3,5], which requires refrigerators with a certain storage capacity and is not practicable for sample distribution.…”