Multicenter Evaluation of a Chromogenic Substrate Method for Photometric Determination of Prothrombin Time

Abstract

SummaryA multicenter study of a chromogenic substrate method for photometric determination of prothrombin time was conducted in order to evaluate its clinical application. Seven laboratories pailicipaled in the study using a total of 742 plasma samples from 417 patients on oral anticoagulant therapy, 261 healthy subjects and 64 patients with different diseases especially of the liver as well as 30 patients with hereditary deficiency of coagulation factors II, V, VII, X. The chromogenic PT method was compared to a standardized coagulometric PT assay which uses the same sensitive human placenta thromboplastin calibrated against international reference preparations. A high correlation of the prothrombin ratio values of the chromogenic and the coagulometric assay was obtained in 402 plasma samples (r = 0.940; y = 1.02x − 0.1). The study showed that the chromogenic PT reagent is sensitive to deficiency of the coagulation factors of the extrinsic pathway but not affected by heparin up to 1 IU/ml because of the heparin antagonist added. The precision (coefficient of variation) of the photometric method ranged between 0.6 and 3% (intraassay CV) and between 1.4 and 5.8 (interassay CV). The International Sensitivity Index (ISI) obtained for the used lot was 1.09. The therapeutical range in percentage activity for patients in a stable phase of an anticoagulant therapy was found to be from 15 to 27 percent of normal. The results of the clinical evaluation proved the good comparability of the new chromogenic PT test with coagulometric methods, its high factor sensitivity, good reproducibility and easy performance.

Change in von Willebrand factor and carotid intima-media thickness in hypothyroid patients with normal thyroid function after levothyroxine replacement therapy

“…As serum markers of endothelial injury, serum levels of coagulation factor VIII, vWF and TM were determined as described previously (1). Coagulation factor VIII was measured using a chromogenic substrate method for photometric determination of prothrombin time as previously described (27). vWF was measured as described previously (28,29).…”

Increased retinal blood flow in patients with Graves' disease: influence of thyroid function and ophthalmopathy

“…Serum thrombomodulin was determined by a one-step sandwich enzyme immunoassay, the sensitivity of which is 1 mg/l for soluble thrombomodulin as previously described (23,24). Coagulation factor VIII was measured using a chromogenic substrate method for photometric determination of prothrombin time as described previously (25). Von Willebrand factor was measured as described previously (26,27).…”

Hypercoagulability and Secondary Hyperf ibrinolysis May Be Related to Abnormal Lipid Metabolism in Patients Treated with Continuous Ambulatory Peritoneal Dialysis

“…FIX was mea sured by the chromogenie activated partial thromboplastin time method using human congenital FIX-deficient plasma and a chromogenic substrate specific for thrombin (Pathochrom; Behringwcrke. Marburg, Germany), as described previously [6]. FV1I and FX were assessed by the chromogenic prothrombin time method using human congenital FVII-or FX-deficient plasma and a chromogenic sub strate specific for thrombin (Chromoquick; Behringwerke), as de scribed previously [6].…”

“…Marburg, Germany), as described previously [6]. FV1I and FX were assessed by the chromogenic prothrombin time method using human congenital FVII-or FX-deficient plasma and a chromogenic sub strate specific for thrombin (Chromoquick; Behringwerke), as de scribed previously [6]. The PT was determined by Quick's test as reported by Miale and Lafond [7], AT-III, Pig, t-PA, and co-PI were assayed by the chromogenic substrate methods of Scully and Kakkar [8].…”