Until the middle of the 90ies, TEM^®/TEG^® analysis was mainly used without the addition of an activator. The only activation was the contact of the blood with the surfaces of pin and cup and eventually the addition of calcium ions.

The resulting assay (non-activated TEM = NATEM) is very sensitive towards almost any kind of coagulation activation or inhibition in the sample and provides an overview over the entire haemostasis process. Only a buffered, specifically concentrated calcium chloride solution (STARTEM) is added.

However, NATEM analysis is more time-consuming and the specificity is lower. There is evidence that the sample quality is more important for this test than for activated methods. star-TEM^® is also used in INTEM and EXTEM assays as recalcification reagent.