The role of coagulogram in clinical practice
A preliminary coagulation test is prescribed when a manifest form of cytomegalovirus infection is suspected. In patients with chronic viral hepatitis B (Hepatitis B virus), a coagulogram is performed strictly according to indications—only in the presence of hemorrhagic syndrome to provide timely care.
The basic panel includes:
- Clotting time of unstabilized blood or plasma recalcification time.
- Bleeding time.
- Prothrombin time.
- Thrombin time.
- Calculated parameters PTI and INR.
When hemorrhagic syndrome develops, blood fibrinogen levels drop and the activity of clotting factors II, V, VII, VIII, IX, and X decreases. The blood clotting time is prolonged, accompanied by a decrease in prothrombin time and a drop in PTI.
Assessment of the extrinsic pathway: PT, PTI, and INR
These parameters reflect the time of clot formation after adding tissue factor to plasma, indicating the function of the extrinsic and common coagulation cascades.
- Prothrombin time (PT). The healthy range is 11–16 seconds.
- International normalized ratio (INR). A standardized index of the rate of extrinsic pathway activation. Normal range is 0.8–1.3.
- Prothrombin index (PTI). Calculated as a percentage, normal values range from 70 to 130%.
Prolongation of these markers indicates DIC, liver damage (including cholestasis), vitamin K deficiency, fat malabsorption, or anticoagulant therapy. Shortening may be associated with physiological processes (pregnancy), blood collection artifacts, prolonged plasma storage, or hematocrit abnormalities.
Assessment of the intrinsic pathway: aPTT
aPTT (activated partial thromboplastin time) indicates the efficiency of the intrinsic coagulation pathway. The test evaluates fibrinogen, prothrombin, and factors 5, 8, 9, 10, 11, and 12. It is important to remember that factors 7 and 13 are excluded from this process. Norms vary by laboratory, approximately 30–40 seconds.
aPTT is prolonged in hemophilia, von Willebrand disease, vitamin K deficiency, liver pathologies, and during the second and third phases of DIC. A decrease in the parameter is typical for acute blood loss, malignant tumor metastasis, and the initial stage of DIC.
Thrombin time, D-dimers, and fibrinogen
- Thrombin time (TT): reflects the final stage—the conversion of fibrinogen to fibrin under the action of exogenous thrombin. Normal range is 14–20 seconds. Prolonged in primary amyloidosis, hypofibrinogenemia, and heparin therapy.
- Fibrinogen: a soluble plasma protein (normal range 2–4 g/L). Sharply increases in acute and chronic inflammation, tumors, and thromboembolism.
- D-dimers: small protein fragments remaining after fibrin breakdown. The test is ordered to rule out DIC, deep vein thrombosis, and pulmonary embolism.
To avoid confusing the tests: the extrinsic coagulation pathway (associated with tissue factor "from the outside") is assessed via PT, PTI, and INR. The intrinsic pathway (all reactions inside the blood) is evaluated using aPTT.
Class and exam questions
In what cases is a detailed coagulogram ordered?
The physician is required to order a detailed hemostasis panel if the screening prothrombin index (PTI) falls below 70%.
Why might prothrombin time be shortened?
This may be a consequence of pregnancy, the first phase of DIC, or an increased concentration of antithrombin III. Preanalytical errors are also a frequent cause: faulty blood collection or prolonged storage of plasma in the refrigerator.
What does prolonged aPTT indicate?
It indicates a dysfunction of the intrinsic and common coagulation pathways. This is characteristic of hemophilia, liver disease, vitamin K deficiency, von Willebrand disease, and anticoagulant therapy.
Why are D-dimers measured?
These are products of thrombus breakdown. The main diagnostic value of the test lies in the fact that its negative result allows thrombosis to be confidently ruled out.
What else to study on this topic
- DIC: staging of changes in the coagulogram (from hypercoagulation to hypocoagulation).
- Specific diagnostics of viral hepatitis (HBsAg, HBeAg, anti-HBe markers).
- Mandatory screening for immunodeficiency viruses (HIV-1, HIV-2) and hepatitis C when HBsAg is detected.
- Assessment of liver biochemical enzymes (ALT, AST, GGT, ALP) and protein metabolism in hemostasis disorders.
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