Effect of dipotassium-ethylenediaminetetraacetic acid or lithium-heparin treatments and storage times on selected clinicopathologic analytes in equine synovial fluid.

Abstract

Sample processing methods and storage time affect the outcome of biochemical analysis. We aimed to assess the effects of dipotassium-ethylenediaminetetraacetic acid (K2-EDTA) and lithium-heparin treatments and storage times on selected analytes in equine synovial fluid (SF). Approximately 2 mL of SF from each horse (n = 7) were collected via femoropatellar joint arthrocentesis into K2-EDTA-treated bottles (K2-EDTA group), lithium-heparin-treated bottles (heparin group), and plain bottles (control group). The pH was determined using an electronic bench pH meter. The total nucleated cell count (TNCC) of samples was determined by hemocytometer method, while total protein (TP) concentrations, and lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) activities of the samples were determined spectrophotometrically at 2, 8, 24, 48, and 168 hours postcollection while being maintained at approximately 4°C. TP concentrations in the anticoagulant-treated groups remained stable for 48 hours. TNCCs were stable for 8 hours. However, after 2 hours, ALP, LDH, and pH varied significantly (P < 0.05). At 2 hours, mean ALP and LDH activities were significantly elevated in the lithium-heparin treatment samples, while the activity of these analytes was similar in the K2-EDTA and control groups. At 8 hours, the TNCC and pH were significantly elevated in K2-EDTA treated groups, while values were similar in lithium-heparin and control groups. No significant variation was seen in TP values at 2 hours, irrespective of treatment. The analytes-except for TP-became unstable within a few hours postcollection. Lithium-heparin and K2-EDTA treatments significantly altered ALP, LDH, TNCCs, and pH but not the TP concentrations of equine SF. Studies establishing reference intervals for these analytes based on the anticoagulant used are warranted to limit misinterpretations in clinical or research settings.