Venous stasis and whole blood platelet aggregometry: a question of data reliability and patient safety

The assessment of platelet function by multiple electrode aggregometry (MEA) (Multiplate, Roche Diagnostics GmbH) is common in laboratory hematology. As regards the ISO 15189:2012 international standard, appropriate use of laboratory equipment requires appropriate pre-examination activities (e.g., blood collection). Venous stasis can influence several blood analytes, but the tourniquet time is rarely regarded as a source of variability. Aim of the present study was to evaluate the impact of venous stasis on platelet function by MEA. A total of 6 ml of blood was collected from 20 volunteers into two 3.0 ml Hirudin vacuum tube (Roche Diagnostics GmbH), and subjected to two procedures: procedure 1 (no stasis) - collection after localization of forearm vein by subcutaneous tissue transilluminator device without tourniquet; procedure 2 (stasis) - collection after localization of vein by prior 60 s tourniquet application. Samples were processed on Multiplate, for: ADP-test (without prostaglandin E1), ADP HS-test (with prostaglandin E1), ASPI-test, COL-test, RISTO H-test (high concentration, 0.77 mg/ml), RISTO L-test (low concentration, 0.20 mg/ml), and TRAP-test. The significance of the differences between samples was assessed by Wilcoxon ranked-pairs test. Surprisingly, the results of ADP HS-test, ASPI-test, COL-test, and RISTO H-test appeared unbiased by venous stasis. RISTO L-test, ADP-test, and TRAP-test were significantly biased; the mean percent difference between stasis and no stasis were -7.2% (P = 0.040), -28.4% (P = 0.015), and 1.1% (P = 0.031), respectively. In conclusion, the tourniquet should be avoided when assessing platelet function by MEA.