clot retraction

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Related to clot retraction: clot retraction time, clot retraction test


the act of drawing back, or condition of being drawn back.
clot retraction the drawing away of a blood clot from the wall of a vessel, a stage of wound healing caused by contraction of platelets; it is a function of blood platelets that can be tested to assess platelet viability.

clot retraction

the shrinking of a semisolid mass formed by the coagulation of blood, lymph, or other fluid. A normal standing blood clot is completely retracted in about 24 hours, although the time depends on such factors as the number of platelets in the clot.

Clot Retraction

Synonym/acronym: N/A.

Common use

To assist in the diagnosis of bleeding disorders.


Whole blood collected in a full 5-mL red-top tube.

Normal findings

(Method: Macroscopic observation of sample) A normal clot, gently separated from the side of the test tube and incubated at 37°C, shrinks to about half of its original size within 1 hr. The result is a firm, cylindrical fibrin clot that contains red blood cells and is sharply demarcated from the clear serum. Complete clot retraction can take 6 to 24 hr.


The clot retraction test helps assess the adequacy of platelet function by measuring the speed and extent of clot retraction away from the side of a collection tube without any additives. Platelets play a major role in the process of clot formation. When platelets are adequate in number and function is normal, the blood will form a clot in the collection tube and retract away from the sides of the tube. The blood will appear in a firm, clearly distinguishable clot surrounded by serum, the liquid portion of coagulated blood. When platelets are decreased or their function is impaired, there is very little serum surrounding a soft, poorly demarcated clot. In addition to normal platelets, clot retraction depends on the contractile protein thrombosthenin, magnesium, adenosine triphosphate (ATP), and pyruvate kinase. Clot retraction is also influenced by hematocrit and by fibrinogen structure and concentration.

This procedure is contraindicated for



  • Evaluate the adequacy of platelet function
  • Evaluate thrombocytopenia of unknown origin
  • Investigate the possibility of Glanzmann’s disease
  • Investigate suspected abnormalities of fibrinogen or fibrinolytic activity

Potential diagnosis

Increased in

  • Anemia (severe) (related to inadequate numbers of red blood cells (RBCs) that quickly produce a clot)
  • Hypofibrinogenemia, dysfibrinogenemia, disseminated intravascular coagulation (DIC) (evidenced by rapid formation of a small, loosely formed clot; absence of functional fibrinogen reduces fibrinolysis)
  • Medications like aspirin (related to effect of acetylsalicylic acid as a potentiator of platelet aggregation)

Decreased in

    Glanzmann’s thrombasthenia (related to autosomal recessive abnormality of platelet glycoprotein IIb–IIIa required for platelet aggregation) Polycythemia (related to excessive numbers of RBCs that physically limit the extent to which the clot can retract) Thrombocytopenia (related to inadequate numbers of platelets to produce a well-formed clot) von Willebrand disease (related to deficiency of von Willebrand factor required for platelet aggregation) Waldenström’s macroglobulinemia (related to excessive production of paraproteins that physically obstruct platelet aggregation)

Critical findings


Interfering factors

  • Drugs that may produce a decreased result include apronalide, carbenicillin, and plicamycin.
  • Platelet count less than 30 × 103/mm3, acetylsalicylic acid therapy, altered fibrinogen/fibrin structure, hypofibrinogenemia, polycythemia or hemoconcentration, and multiple myeloma are conditions in which abnormal clot retraction may occur, limiting the ability to form a valid assessment of platelet function.
  • Prompt and proper specimen processing, storage, and analysis are important to achieve accurate results. Specimens received in the laboratory more than 1 hr after collection should be rejected.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:  Inform the patient this test can assist in evaluating the effectiveness of blood clotting.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s hematopoietic system and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues,  as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory within 1 hr of collection for processing and analysis. The specimen must be promptly placed in a 37°C waterbath to simulate the temperature at which hemostasis would occur in the body, and it must be observed at 2 and 24 hr. Normally, a clot will form and extrude serum within 1 to 2 hr. In addition to normal platelet count and function, clot formation is dependent on a normal RBC volume (hematocrit) and a sufficient concentration of fibrinogen.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Inform the patient with abnormal clot retraction of the importance of taking precautions against bruising and bleeding. These precautions may include the use of a soft bristle toothbrush, use of an electric razor, avoidance of constipation, avoidance of acetylsalicylic acid and similar products, and avoidance of intramuscular injections.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include bleeding time, coagulation factor XIII, CBC, CBC hematocrit, CBC hemoglobin, CBC platelet count, and fibrinogen.
  • Refer to the Hematopoietic System table at the end of the book for related tests by body system.


1. a semisolidified mass, as of blood or lymph.
2. to form such a mass.

dilute whole blood clot retraction test
an indirect measure of fibrinolytic activity. Whole blood is diluted with saline, chilled, then warmed. The time for clot retraction, and later clot lysis, is measured.
clot formation
a complex interaction, part of the phenomenon of blood clotting. The process is irreversible but the clot may be dissolved naturally.
clot lysis
the time required for a clot to lyse at 98.6°F (37°C) is a reflection of the plasmin content of the blood. Clot retraction and fibrinogen content of the blood sample are also influential.
clot retraction
the drawing away of a blood clot from a vessel wall, a function of thrombasthenin, released by blood platelets.
clot retraction test
a test for platelet numbers and function. Clotted whole blood should retract away from the sides of a glass tube in 1 to 2 hours.


the act of drawing back, or condition of being drawn back.

clot retraction
see clot retraction.
References in periodicals archive ?
Lavender oil, as well as linalyl acetate, completely inhibited clot retraction induced by thrombin in rat PRP at a concentration as low as 270 [micro]g/ml (Fig.
An analogue consideration could be done for clot retraction even if the main component of the phytocomplex, linalyl acetate, seems to primarily contribute to lavender oil effect being as potent as the whole essential oil.
Not only inhibition of platelet aggregation but also clot retraction are critical factors for the activity of antithrombotic drugs.