Disposables and reagents available

Our recommendation is that this POC instrument’s most valuable feature is the ability to show the behaviour of native clotting blood. Most of the answers needed regarding the majority of cases will be obtained from such analysis. Therefore we recommend to run thromboelastography tests on native blood. However there are cases where the response of the instrument may be helpful even when the blood sample has been modified with a reagent. When doing such analysis it should be very clear that the results are influenced by further handling of the sample (= shear, temperature) and by the effect of the added reagent product: although the biochemical effects on the blood sample may be known, the effect on the mechanics of clotting are not fully explored, thus there might be secondary mechanical effects that are not evident.

Another thought is worth considering when planning for thromboelastography with reagents : these tests requires already a good dose of precision and attention, oftentimes in the hospital work is hectic and lengthy analysis procedures cannot be run without risks of inter-operator variances. Laboratory personnel is more adapted to these procedures, therefore we recommend that TEM-A be used as a POC in the ORs/ICUs for routine analysis on native blood, whilst whenever further analysis with reagents are required, these be carried out by professionals of the lab, most probably in a lab environment. It should be clear that the valuable responses of this instrument as a POC on native blood samples are obtained with a simple procedure, whilst the responses obtained from further handling of the blood sample require more lengthy and precise protocols to assure a valuable contribution to the clinical diagnosis. Any analysis with reagents has been tested for specificity and sensitivity, these test have been run in a lab environment, not in an ICU !

Blood samples can be treated with a number of various reagents, depending on the investigation that is necessary. Typically, in presence of heparin or LMWH, it is possible to abrogate the heparin content in the blood by mixing the sample with the enzyme heparinase and look at the clotting behaviour as if heparin was absent. Therefore by comparing two thromboelastography tests, one with heparinase against one without heparinase it is possible to determine if post-op protamine was adequate and/or, to investigate heparin resistance, if there is a suspect of AT deficiency.

Treating the sample with TF would stimulate the extrinsic coagulation pathway, producing a fast and reliable response on the MA (Maximum Amplitude) that expresses the functionality of platelets, however the reliability of other TEM-A thromboelastography parameters would be compromised.

Blood samples can be treated with other reagents to investigate platelet aggregation, procedures that can be performed knowledgeably in the laboratory as they involve measurements and calculations made on several analysis on samples treated with different reagents. See para “Special Analysis” herunder.