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[Monitoring of coagulation status in the physician's laboratory]
1Hämostaselabor DZL, Kantonsspital Basel.
The usual coagulation tests performed in the medical practitioner's office are the prothrombin time (PT) and, less frequently, the activated partial thromboplastin time (aPTT, PTT), PT and aPTT are used as screening tests for coagulation disorders and for the monitoring of oral anticoagulation or home treatment with unfractionated heparin, respectively. Considered a 'simple test', the PT requires important conditions to be fulfilled by the laboratory. The results expressed in seconds, as a ratio, as PT-index and in activity percentages depend on the PT method and its local adaptation. The only way to communicate the intensity of oral anticoagulation to other doctors, hospitals and countries is to convert the PT seconds into international normalized ratios (INR). This requires the determination of the mean normal prothrombin time by each laboratory and the knowledge of the appropriate international sensitivity index (ISI). Reference curves are needed for PT expression as activity percentages. The PT of capillary blood deserves special consideration. Test performance is guided by regular internal and external quality control procedures.
The usual coagulation tests performed in the medical practitioner's office are the prothrombin time (PT) and, less frequently, the activated partial thromboplastin time (aPTT, PTT), PT and aPTT are used as screening tests for coagulation disorders and for the monitoring of oral anticoagulation or home treatment with unfractionated heparin, respectively. Considered a 'simple test', the PT requires important conditions to be fulfilled by the laboratory. The results expressed in seconds, as a ratio, as PT-index and in activity percentages depend on the PT method and its local adaptation. The only way to communicate the intensity of oral anticoagulation to other doctors, hospitals and countries is to convert the PT seconds into international normalized ratios (INR). This requires the determination of the mean normal prothrombin time by each laboratory and the knowledge of the appropriate international sensitivity index (ISI). Reference curves are needed for PT expression as activity percentages. The PT of capillary blood deserves special consideration. Test performance is guided by regular internal and external quality control procedures.