TEG PlateletMapping assay results may be misleading in the presence of cold stored platelets

BACKGROUND Viscoelastic tests (VETs) are used widely to monitor hemostasis in settings such as cardiac surgery. There has also been renewed interest in cold stored platelets (CSPs) to manage bleeding in this setting. CSPs are reported to have altered hemostatic properties compared to room temperature platelets (RTPs), including activation of GPIIb/IIIa. We investigated whether the functional differences between CSP and RTP affected the performance of the PlateletMapping VET on the TEG 5000 and 6s analyzer. METHOD Platelet concentrates were divided equally into CSP (stored at 4 degrees C +/- 2 degrees C) and RTP (stored at 22 degrees C +/- 2 degrees C) fractions. Whole blood was treated to induce platelet dysfunction (WBIPD) by incubating with anti-platelet drugs (1.0 mu M ticagrelor and 10 mu M aspirin) or by simulating cardiopulmonary bypass. WBIPD samples were then mixed with 20% by volume of CSPs or RTPs to model platelet transfusion before analysis using the PlateletMapping VET. RESULTS Addition of CSPs to WBIPD increased the PlateletMapping MA(FIBRIN) and MA(ADP) parameters with the TEG 5000 analyzer (both p < 0.0001 compared to addition of buffer alone). This effect was not observed with RTPs. The differential effect of CSPs on the MA(FIBRIN) corrected after pre-incubation with the GPIIb/IIIa antagonist tirofiban and was quantitatively less with the PlateletMapping test for the TEG 6s analyzer which contains the GPIIb/IIa antagonist abciximab. DISCUSSION The PlateletMapping MA(FIBRIN) and MA(ADP) test results may be misleadingly high with CSPs, particularly with the TEG 5000 analyzer, most likely due to constitutive activation of GPIIb/IIIa on CSPs during storage. TEG PlateletMapping results should be interpreted with caution following CSP transfusion.