Thrombin time coagulogram

Initial assessment of the hemostatic system

For the primary evaluation of the blood coagulation system, patients are recommended to undergo a basic coagulogram. This comprehensive screening test provides a general overview of hemostasis function.

The mandatory panel of investigated parameters includes the following tests:

• Coagulation time of non-stabilized blood or plasma recalcification time (unactivated).
• Bleeding time.
• Prothrombin (also known as thromboplastin) time, which can be determined in either whole blood or plasma.
• Thrombin time in blood.
• Determination of the International Normalized Ratio (INR).

This standardized set of tests serves as the starting point for diagnosing any abnormalities in the coagulation system and determining the patient's further diagnostic pathway.

Role of the coagulogram in acute promyelocytic leukemia (APL)

In the management of patients with acute promyelocytic leukemia (APL), hemostasis monitoring is of critical importance. Assessment of the coagulation system is indicated for absolutely all patients with this diagnosis. It is important to note that testing must be performed both prior to the initiation of specific treatment and during therapy.

The required minimum of tests for APL includes:

• Screening coagulogram.
• Activated partial thromboplastin time (APTT).
• Prothrombin time (in blood or plasma).
• Thrombin time.
• Blood fibrinogen level.

The main goal of such meticulous monitoring is the timely diagnosis of potential complications, detection of comorbid pathology, and, most importantly, the correct selection of supportive therapy tactics. According to clinical protocols, this recommendation has an evidence grade of C (level of evidence certainty — 5).

Differential diagnosis in immune thrombocytopenia

Patients with suspected immune thrombocytopenia (ITP) are also strictly recommended to undergo a coagulogram. The main objective in this case is to perform a differential diagnosis between ITP and other potential hemostatic disorders.

For this category of patients, an extended coagulogram is used, which includes:

• Activated partial thromboplastin time (aPTT).
• International Normalized Ratio (INR) and/or Quick's prothrombin.
• Thrombin time (TT).
• Fibrinogen concentration.
• Antithrombin III.
• Natural anticoagulants: protein C and protein S.
• Von Willebrand factor.

The completeness of this study makes it possible to rule out congenital and acquired coagulopathies masking as immune thrombocytopenia. This practice is also based on a level of evidence of 5 (LoE C).

Additional tests to rule out complications

In addition to standard hemostasis parameters, additional laboratory markers are used for a comprehensive assessment of the patient's condition and the complete exclusion of severe complications. Specifically, the expanded panel includes determining the concentration of D-dimer along with INR, APTT, and thrombin time.

In parallel with the coagulogram, the attending physician may prescribe:

1. Direct antiglobulin test (direct Coombs test). This test is critically important for clarifying the patient's predisposition to hemolytic complications, which is especially relevant in the context of chronic lymphocytic leukemia (CLL).
2. General urinalysis (UA).

A comprehensive approach combining the coagulogram, Coombs test, and general clinical analyses ensures high accuracy in identifying the risks of bleeding or thrombosis.

Class and exam questions

What else to study on this topic

• Clinical significance of APTT and prothrombin time in initial screening
• Method for determining the clotting time of non-stabilized blood
• The role of D-dimer in the diagnosis of occult hemostatic system complications
• Proteins C, S, and antithrombin III: function in the coagulation cascade
• Differential diagnosis of immune thrombocytopenia and von Willebrand factor disorders

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.