Systematic evaluation of evidence on veterinary viscoelastic testing part 3: Assay activation and test protocol.

Objective: To systematically examine the evidence on activating agents and test protocols for the thrombelastography (TEG) and rotational thrombelastometry (ROTEM) viscoelastic point-of-care instruments and to identify knowledge gaps.

Design: Ten questions were considered, the primary question addressed the use of activating agents and secondary questions addressed assay temperature, length of analysis, pipetting, sample volume, reproducibility, and quality controls. Standardized, systematic evaluation of the literature was performed. Relevant articles were categorized according to level of evidence (LOE). Consensus was developed regarding conclusions for application of concepts to clinical practice.

Setting: Academic and referral veterinary medical centers.

Results: PubMed and CAB abstracts were searched. Twenty papers were initially identified concerning the primary question; 16 were in support of the questions (LOE 2 Good, LOE 3 Good, LOE 5 Good, LOE 6 Good, LOE 5 Fair, LOE 6 Fair); and 4 were neutral (LOE 3 Good, LOE 6 Good, LOE Fair, LOE 5 Fair). Additional papers were evaluated post hoc during manuscript preparation.

Conclusions: Overall, there is a body of evidence from veterinary and human medicine that strongly suggests that TEG or ROTEM assays using citrated samples that employ an activator have significantly lower inherent variability than those that use recalcification alone. There is also strong evidence in dogs, cats, and humans that the results obtained using different activators are not directly comparable. There is no evidence to suggest that any one activating agent is superior to another for all patient populations, or drug monitoring indications. As such, use of more than one assay for complete thromboelastographic evaluation of a patient's coagulation system may be warranted. Standardization of the concentrations of activators would be beneficial.