Clinical implications of synovial fluid specimen handling for crystal associated arthritides: A systematic review

Abstract

Aim: To identify the appropriate methods of synovial fluid (SF) specimen storage, manipulation and handling for crystal associated arthritides (CAA) diagnosis. Method: A systematic literature review was conducted using 5 medical databases to identify diagnostic studies assessing SF specimen handling for calcium pyrophosphate (CPP) and monosodium urate (MSU) crystals identification. All included studies were rated for quality using the Quality Assessment of Diagnostic Accuracy Studies 2. Results: Fifteen studies, including 2 non-English language manuscripts, were included. Eight studies examined both types of crystals, while 3 studies examined CPP and 4 studies examined MSU crystals only. Overall, MSU crystals were more stable over time compared to CPP crystals. MSU stability was generally independent of time, preservative and temperature. CPP crystals deteriorated with time and were more stable if refrigerated. Ethylenediaminetetraacetic acid (EDTA) was a suitable preservative. Reexamining an initially negative SF sample at 24 hours facilitated detection of additional cases. Very few studies had an overall low risk of bias and applicability. Conclusion: Monosodium urate crystals remain stable over time independent of storage time, temperature and preservative. CPP crystals are mostly stable for 24-48 hours but can deteriorate with time. Overall, SF crystal examination should ideally be done within 24-48 hours. They may be stored at room temperature without any preservative. Otherwise, refrigeration (4°C/39°F) and EDTA preservation is reasonable. Stored SF re-examination, at 24 hours, helps identify a small number of additional MSU and CPP cases. Centrifugation techniques allow better and easier crystal identification, particularly CPP. Most studies were of unclear or low quality.

Diagnosis, Treatment, and Outcomes of Crystalline Arthropathy in the Setting of Total Knee Arthroplasty

“…Table II outlines the different arthrocentesis findings for gout, CPPD disease, and PJI 24,31-33 . Synovial fluid results showing MU crystals or CPP crystals remains the gold standard for the diagnosis of gout and CPPD disease, respectively 34-36 . Although not specific to gout and CPPD disease, the identification of crystals on aspiration should alert the surgeon to the possibility that symptoms are being caused by CA and not PJI.…”

“…Table II outlines the different arthrocentesis findings for gout, CPPD disease, and PJI 24,[31][32][33] . Synovial fluid results showing MU crystals or CPP crystals remains the gold standard for the diagnosis of gout and CPPD disease, respectively [34][35][36] .…”

Presence of Crystals in the Synovial Fluid of Patients With Psoriatic Arthritis

“…Critical assessment of counting molded elements -the total and differential number of white blood cells in synovial fluid provides a way of distinguishing between noninflammatory and inflammatory arthritis, neutrophil rates are a good guide to the degree of inflammation of the joints and therefore an indicator of severe acute conditions (15,18) C. Critical assessment of the identification of MSU, CPPD crystals, etc. through polarized light microscopy -analysis of the sensitivity, specificity and reliability tests of crystals shows alarming problems and variations (15,16,19,20).…”