Plasma tissue factor antigen levels in capillary whole blood and venous blood: Effect of tissue factor on prothrombin time

✍ Scribed by Quien, Emmanuel T.; Morales, Enid; Cisar, Laura A.; Kim, Hugh C.; Cimini, Catherine; Saidi, Parvin; Philipp, Claire S.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 45 KB
• Volume: 55
• Category: Article
• ISSN: 0361-8609
• DOI: 10.1002/(sici)1096-8652(199707)55:4<193::aid-ajh5>3.0.co;2-n

✦ Synopsis

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.