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Crystals, synovial fluid
|Performed by||Parnassus Hematology|
|In House Availability||Test run 0800-2400 daily|
|Method||Compensated Polarized Light Microscopy|
|Collection Instructions||Specimen label must contain the date and time the sample was collected and the legible name of the person who collected the sample.
Bring samples asap to laboratory for testing.
|Container type||Lavender or Dark Green top|
|Amount to Collect||See preferred volume|
|Sample type||Synovial fluid|
|Preferred volume||1 ml fluid|
|UCSF Rejection Criteria||Samples in syringes with needle still attached.
Samples received four (4) or more hours after collection are accepted but results modified as follows: "Sample stability period exceeded or collection time unknown. Calcium pyrophosphate dehydrate (CPPD) crystals dissolve with time, therefore false negatives can occur. Uric acid crystals are stable for several weeks. See Lab Manual for Moffitt-Long and Mt. Zion for more information".
|Processing notes||Deliver sample to Hematology immediately after sample is received and entered in Sunquest.|
|Synonyms||Gout; Uric acid; Pseudogout; Calcium pyrophosphate dehydrogenase; CPPD; joint fluid|
|Stability||4 hours at room temperature|
|Turn around times||4 hours|
|Additional information||Included routinely when a Cell Count & Differential is ordered on joint fluid. There is a > 95% chance of detecting intraleukocytic urate crystals in an acutely gouty joint (and in approx. 75% of asymptomatic patients); the few negative fluids are usually positive on repeat aspiration a few hours later. False positive results can occur due to the similar needle- or rod-like shape and birefringence seen occasionally w/ cholesterol crystals or w/ crystalline preparations of corticosteroids such as betamethasone and triamcinolone. Cartilage fragments and calcium oxalate crytals can also be birefringent, but are usually distinguishable from urates by careful attention to morphologic details. Generally more rectangular birefringent pyrophosphate crystals are seen in other arthritides.
Lithium heparin (light green top) may cause false positive crystal formation.
Based on a small in-house study the effect of storage on joint crystals was examined. Calcium pyrophosphate dehydrate (CPPD) crystals dissolve after several hours. Refrigeration did not prevent CPPD crystals from dissolution. However, Monosodium Urate (MSU) crystals did not decrease in numbers significantly over the first few days, but decrease over a period of weeks. Refrigeration appeared to slow the dissolution of MSU crystals.
Samples for Particle Disease – Particle disease is a byproduct of the increasing use of prosthesis for joint replacement in patients with chronic arthritis. Looking at joint fluid for particles is not ideal for diagnosis of "particle disease", but is the simplest means of obtaining a sample (much easier than biopsy of tissue around the prosthetic joint).
|Last Updated||3/24/2013 8:12:30 PM|