title: Plasma tissue factor antigen levels in capillary whole blood and venous blood: effect of tissue factor on prothrombin time.
abstract: To measure the amount of tissue factor released during specimen collection and its potential effect of shortening the prothrombin time, we measured tissue factor and prothrombin time in twenty-three paired venous and capillary blood samples from anticoagulated patients and in ten paired samples from controls. We also compared venous prothrombin time determined by a plasma-based assay with venous and capillary prothrombin time determined with a whole blood assay. Venous specimens were obtained using a two-syringe technique; capillary specimens were obtained by fingerstick after wiping the first drop of blood. Plasma tissue factor was determined by an enzyme-linked immunoabsorbant assay. The patients' mean venous tissue factor (235 +/- 101 pg/ml) and capillary tissue factor (268 +/- 106 pg/ml) were higher than those of the controls (161 +/- 42 pg/ml and 187 +/- 63 pg/ml, respectively, P < 0.05). These differences disappeared after adjusting for age. Capillary tissue factor levels were higher than venous tissue factor (244 +/- 102 pg/ml vs. 213 +/- 93 pg/ml), with a mean difference of 31 pg/ml (P = 0.0001). In addition, whole blood prothrombin time was lower in the capillary than in the venous samples (17.7 +/- 5 sec vs. 18.3 +/- 5.4 sec, P = 0.004). However, there was no correlation between capillary-venous differences in tissue factor and capillary-venous differences in the whole blood prothrombin time. Whole blood capillary and venous prothrombin times highly correlated with the plasma-based venous prothrombin time (r = 0.98, P < 0.0001). These results demonstrate that obtaining blood by fingerstick does not result in a clinically significant release of tissue factor. In addition, we did not observe any interference of plasma tissue factor with the whole blood prothrombin time assay. A direct relationship between tissue factor and age was observed.
authors.affiliation: Division of Hematology, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School, New Brunswick 08903, USA.
authors.forename: E T
authors.initials: ET
authors.lastname: Quien
authors.forename: E
authors.initials: E
authors.lastname: Morales
authors.forename: L A
authors.initials: LA
authors.lastname: Cisar
authors.forename: H C
authors.initials: HC
authors.lastname: Kim
authors.forename: C
authors.initials: C
authors.lastname: Cimini
authors.forename: P
authors.initials: P
authors.lastname: Saidi
authors.forename: C S
authors.initials: CS
authors.lastname: Philipp
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use; D000941:Antigens / Q000097:blood; D001800:Blood Specimen Collection; D002196:Capillaries; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time; D013925:Thromboplastin / Q000032:analysis* / Q000502:physiology*; D014680:Veins; D014859:Warfarin / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D000941:Antigens; D014859:Warfarin; D013925:Thromboplastin