Prothrombin time


The exogenous coagulation system is activated by addition of tissue-thromboplastin and calcium to citrated plasma. Prothrombin time is measured as the time until clotting. In analogy to activated partial thromboplastin time, (aPTT) the prothrombin time is the global test for the extrinsic system. The speed of the fibrin formation is thus above all dependent of the activity of the factors II, VII and X.
Factor V and fibrinogen are of less importance.

Thromboplastins are tissue extracts of various origins. They consist of a protein and a phospholipid part. Thromboplastins are now produced recombinantly. The sensitivities of the reagents differ considerably. For this reason, results originating from assays made with different thromboplastins are not comparable.

Analyses by the Quick-method (by A. J. Quick, 1935) are mostly carried out in a geometrical range of dilutions with physiological sodium chloride using a normal plasma pool to create a reference curve. The resulting clotting time (Prothrombin time) of the patient sample is then related to the calibration curve and reported in percent of normal value.

In order to obtain a better comparability of the measurement results, the WHO  introduced the INR (International Normalized Ratio) in 1983. The ISI-value (International Sensitivity Index) shows the sensitivity of the used reagent against a standard-thromboplastin.


  • Monitoring of therapy with Vitamin K-antagonists
  • Suspected factor deficiency in the extrinsic system


  1. Barthels M, Poliwoda H. Gerinnungsanalysen 5. Aufl. Stuttgart: Thieme 1997.
  2. DIN 58911. Teil 1 Hämostaseologie. Kalibrierung von Meßverfahren. DIN-Taschenbuch 261. Berlin: Beuth 1996.
  3. Hirsh J. Guide to anticoagulant therapy, part 2: oral anticoagulants. Circulation 89, 1469, 1994.
  4. Kemkes-Matthes B, Matzdorff A, Heidt M et al. Initialphase der oralen Antikoagulanzientherapie: Vergleich verschiedener Dosierungen von Warfarin und Phenprocoumon. Hämostaseologie 22, 87–91, 2002.
  5. Müller-Beißenhirtz W, Deickert F, Lang H et al. Selbstkontrolle der oralen Antikoagulation: Standortbestimmung. Hämostaseologie 18, 84–88, 1998.
  6. Witt I, Beeser H, Lang H, Müller-Beißenhirtz W. Thromboplastinzeit und INR: Standardisierung der Methode, Anwendung zur Kontrolle der oralen Antikoagulanzientherapie und als Globaltest der plasmatischen Gerinnung – Standortbestimmung. J Lab Med 20, 443, 1996.
  7. Walborn A, Williams M, Fareed J, Hoppensteadt D. International Normalized Ratio Relevance to the Observed Coagulation Abnormalities in Warfarin Treatment and Disseminated Intravascular Coagulation. Clin Appl Thromb Hemost Oct 24 1033-1041, 2018.
  8. Nilsson CU, Strandberg K, Reinstrup P. Warfarin monitoring with viscoelastic haemostatic assays, thrombin generation, coagulation factors and correlations to Owren and Quick prothrombin time.Scand J Clin Lab Invest. May 23, 1-7, 2018.
Test kits
Coagulation Assays

Technoplastin® HIS

Short Info Request personal insert

Technoclot® PT Plus

Short Info Request personal insert

Tecnoclot® PT Owren manual

Short Info Request personal insert

Technoclot® PT Owren automated

Short Info Request personal insert

We are here for you

Haemochrom Diagnostica GmbH
Renteilichtung 1
45134 Essen

Phone: +49 (0)201 8 43 77-0
Fax: +49 (0)201 53 64 56

Send us a message