CLOT RETRACTION, Qualitative, Quantitative Method for Clot Retraction

CLOT RETRACTION

Normal blood clots completely in 5-10 minutes. The clot begins to retract in one hour, and the clot retraction should be complete within four hours, separating itself from serum. Normal clot retraction is indicative of normal platelet function.

Qualitative Method for Clot Retraction 

(1) Collect 5-10 ml of blood directly into a clean glass test tube. 

(2) Place the tube in a water bath at 37°C. 

(3) Observe the clot retraction periodically for up to 24 hours.

Quantitative Method for Clot Retraction

Specimen Collect 10 ml of blood in a graduated centrifuge tube and 2ml in an EDTA tube. 

Technique 

(1) Place an applicator stick into the blood in the centrifuge tube before it clots.

(2) As soon as it clots, place it in a waterbath at 37°C for exactly one hour.

(3) Withdraw the clot by gently removing the applicator stick, leaving the serum and some free cells in the tube.

(4) Note the characteristics of the clot if it is firm or friable; and also note the clot retraction if complete or poor.

Measure the volume of the serum and cells in the tube, expressed from 10 ml of blood:

Determine the haematocrit value of the blood sample either by Wintrobe's or microhaematocrit method using the EDTA anticoagulated blood.

In case of normal individuals, the clot retraction is completed in four hours.

In patients with abnormal platelet function, the clot retraction is delayed and may be poor or absent after 24 hours.

Normal range 58-97% in one hour Interpretation Decreased clot retraction may be observed in a number of platelet defects. It is lowered in thrombocytopenia.