Causes of increase and shortening of prothrombin time

The increase in prothrombin time indicates a tendency to hypocoagulation and may depend on various causes.

• Insufficiency of one or several factors of the prothrombin complex, which is observed with such hereditary coagulopathies as hypoproconvertinemia (factor VII deficiency) and hypoprothrombinemia (Factor II deficiency).
• Sometimes the increase in prothrombin time observed in amyloidosis is associated with a deficiency of factor X, which is absorbed by amyloid, and in nephrotic syndrome - with deficiency of factors VII and V, which are excreted in the urine.
• Synthesis of the factors of the prothrombin complex occurs in the liver cells, with the latter the number of them decreases, so prothrombin time to a certain extent can serve as an indicator of the functional state of the liver. An increase in prothrombin time is noted in acute and chronic hepatitis, cirrhosis of the liver, subacute liver dystrophy and other lesions of the liver parenchyma, which is considered a poor prognostic sign. At the same time, the increase in the prothrombin time can be caused by a decrease in the intake of bile in the intestine, a violation of absorption of vitamin K, which is necessary for the synthesis of factors of the prothrombin complex. The same is the cause of the increase in prothrombin time and with mechanical jaundice.
• Enteropathy and intestinal dysbiosis, leading to vitamin K deficiency, may also be accompanied by an increase in prothrombin time.
• When treating vitamin K antagonists (indirect anticoagulants), the final stage of synthesis of the prothrombin complex factors is disrupted, and the prothrombin time is prolonged.
• The consumption of factors of the prothrombin complex with acute DIC syndrome leads to a rather early increase in prothrombin time (2 times or more).
• In chronic pancreatitis, pancreatic cancer and gallstones, an increase in prothrombin time can be the result of liver damage and / or the development of DIC syndrome.
• Afibrinogenemia, hypofibrinogenemia (a decrease in the fibrinogen in the blood to 1 g / l and below), as well as an excessive content of heparin in the blood lead to an increase in prothrombin time.
• Elongation of prothrombin time is revealed in acute and chronic leukemias, due to the development of DIC syndrome.
• An increase in the concentration of antithrombin or antithromboplastin in the blood also leads to lengthening of 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.

The shortening of prothrombin time indicates a tendency to hypercoagulable and can be noted in the initial stages of deep vein thrombosis of the lower extremities, with polycythemia, in the last months of pregnancy. The shortening of prothrombin time is caused by the following drugs: acetylsalicylic acid (in small doses), mercaptopurine, oral contraceptives.

[1], [2], [3], [4], [5], [6], [7], [8]