Handling of samples
For determination of cell concentration (cell counts) and cytologic evaluation, fluid should be collected into EDTA tubes (lavender stopper). This prevents clot formation so that accurate cell counts and adequate slides for microscopic evaluation can be prepared.
Total protein, creatinine, bilirubin, triglycerides, and cholesterol can be measured in EDTA-plasma by most assays; only measurement of lipase and lactate dehydrogenase activity is confounded by EDTA, therefore heparinized or native fluid is required. A sterile plain tube should be available when bacterial culture is necessary.Evaluation of the sample should be performed as soon as possible. If samples are submitted to a referral laboratory, native smears and smears of a sediment preparation should be prepared to provide adequate sample quality for cytologic evaluation. If a smear was prepared from a concentrated fluid and submitted, it should be labeled as such. If collection was not sterile, in-vitro growth of bacteria can lead to erroneous results. The samples should be stored at 4°C until evaluation.