Effect of time and temperature on anticoagulant-dependent pseudothrombocytopenia in Göttingen minipigs

Background: A marked decrease in thrombocyte count was observed between subsequent measurements of the same EDTA blood sample in several minipigs, but little information was available explaining this finding.

Objectives: The objective was to evaluate the impact of several preanalytic variables on thrombocyte counts in minipigs, in order to improve understanding of the in vitro thrombocyte decrease observed.

Materials and methods: Hematology blood samples from male and female Göttingen minipigs were collected using EDTA or citrate as an anticoagulant. Samples were stored under different conditions (room temperature, 4°C, or 37-38°C) and were analyzed approximately 0.5 to one h, 3.5-4 h, 7-7.5 h, and 28-29 h after collection.

Results: In EDTA blood samples from male minipigs stored at room temperature, there was a progressive thrombocyte decrease over time up to -71% after 29 h, caused by in vitro aggregation. In females, no consistent change was seen up to 7.5 h, but there was a decrease up to -47% after 29 h. Thrombocyte count was most stable during storage at 4°C. No consistent marked decrease in thrombocyte counts was seen for citrated blood at room temperature, although such a decrease was present in a few individual animals.

Conclusions: Study results provide evidence for an anticoagulant-dependent pseudothrombocytopenia in minipigs progressing over time and depending on the storage temperature of the blood sample. It is therefore recommended to perform thrombocyte counts as soon as possible after blood collection, and in case of low counts, investigate for the presence of artifactual platelet clumping.