Measurement of Thrombin-Alpha-2-Macroglobulin Complexes Generated in Plasma.

Abstract 4205

The aim of this study is to evaluate a new assay (TECHNOZYM®TAM Activity) for measurement of thrombin-alpha2-macroglobulin (TAM) complexes. Furthermore, we asked the question whether the acute phase nature of a2Macroglobulin would be reflected in increased TAM levels in plasma of sepsis patients.

Thrombin generation was measured using TECHNOTHROMBIN®TGA which does not use any inhibitors of clot formation. Thus, clots formed during the reaction need to be removed either by centrifugation or filtration prior to sample transfer to the TAM assay which is a combined immuno-activity assay specifically detecting a2M bound thrombin.

Pre-existing TAM levels in various haemostatic samples did not differ significantly from those in normals, with one exception. Surprisingly, Factor X deficient samples expressed about 3 fold higher levels of TAM than normals. Approximately 4% of total thrombin generated was found in TAM complexes (TAM/AUC ratio 3,6 % ± 1, TAM concentration 73nM ±14). No significant difference in TAM values could be found for the different methods of clot removal (n=8; p>0,3). As expected, thrombin generation in normal as well as in factor deficient samples lead to approximately 10-fold increase of TAM. Only in FX-deficient and Coumadin samples no increase in TAM was observed. This is consistent with the small amount of total thrombin generated in these samples. TAM levels in plasma of sepsis patients were significantly higher (19.2nM ± 1.7) than in normals (9.7nM ±0.5; n=40, p<0,0001). Levels of TGA triggered TAM correlate with total amount of thrombin generated and TAM measurement in TGA samples is not necessary for routine TGA measurements. Furthermore, TAM levels are increased in the plasma of sepsis patients and do not correlate with acute phase markers in these patients. Thus TAM might be suitable as a new marker to differentiate a (sub)group of sepsis patients.