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Causes of increased and shortened prothrombin time
Last reviewed: 04.07.2025
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An increase in prothrombin time indicates a tendency to hypocoagulation and may depend on various causes.
- Deficiency of one or more factors of the prothrombin complex, which occurs in such inherited coagulopathies as hypoproconvertinemia (factor VII deficiency) and hypoprothrombinemia (factor II deficiency).
- The increase in prothrombin time sometimes observed in amyloidosis is associated with a deficiency of factor X, which is absorbed by amyloid, and in nephrotic syndrome, with a deficiency of factors VII and V, which are excreted in the urine.
- Synthesis of prothrombin complex factors occurs in liver cells; in liver diseases, their number decreases, therefore prothrombin time can serve to a certain extent as an indicator of the functional state of the liver. An increase in prothrombin time is observed in acute and chronic hepatitis, liver cirrhosis, subacute liver dystrophy and other lesions of the liver parenchyma, which is considered a poor prognostic sign. In this case, the reason for the increase in prothrombin time can also be the development of a violation of the absorption of vitamin K, which is necessary for the synthesis of prothrombin complex factors, as a result of a decrease in the flow of bile into the intestine. The same reason for the increase in prothrombin time is mechanical jaundice.
- Enteropathy and intestinal dysbacteriosis leading to vitamin K deficiency may also be accompanied by an increase in prothrombin time.
- When treated with vitamin K antagonists (indirect anticoagulants), the final stage of the synthesis of prothrombin complex factors is disrupted, and prothrombin time is prolonged.
- Consumption of prothrombin complex factors in acute DIC syndrome leads to a fairly early increase in prothrombin time (2 times or more).
- In chronic pancreatitis, pancreatic cancer and gallbladder cancer, an increase in prothrombin time may be the result of liver damage and/or the development of DIC syndrome.
- Afibrinogenemia, hypofibrinogenemia (a decrease in the fibrinogen content in the blood to 1 g/l and below), as well as an excess of heparin in the blood lead to an increase in prothrombin time.
- Prolongation of prothrombin time is detected in acute and chronic leukemia, due to the development of DIC syndrome.
- An increase in the concentration of antithrombin or antithromboplastin in the blood also leads to an increase in prothrombin time;
- A whole group of drugs can prolong prothrombin time: anabolic steroids, antibiotics, acetylsalicylic acid (in high doses), laxatives, methotrexate, nicotinic acid, quinidine, thiazide diuretics, tolbutamide.
Shortening of prothrombin time indicates a tendency to hypercoagulation and may be noted in the initial stages of deep vein thrombosis of the lower extremities, with polycythemia, in the last months of pregnancy. Shortening of prothrombin time is caused by the following drugs: acetylsalicylic acid (in small doses), mercaptopurine, oral contraceptives.
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