Activated Partial Thromboplastin Time (PTT) is commonly used for

  • pre-surgical screening for intrinsic factor deficiency,
  • monitoring heparin therapy
  • detection of Lupus Anticoagulants
  • quantitative determination of the Factor VIII, IX, XI, and XII relevant with the intrinsic coagulation system.

Schematic illustration of blood coagulation pathways. 12 Both intrinsic pathway and extrinsic pathway lead to the final common pathway.


In the test, citrated test plasma is mixed with PTT reagent for a specified period of time. The time required for clotting formation is the activated partial thromboplastin time (PTT). The degree of prolongation is proportional to the severity of single factor deficiency, or in a cumulative deficiency of all the factors involved.


MATERIALS PROVIDED:  PTT Liquid Reagent.  Plasma Normal Control.

Specimen collection

  1.  Plasma obtained from whole blood samples that had been collected in a tube with 0.109M sodium citrate as an anticoagulant, nine parts of freshly collected whole blood should be immediately added to one part of anticoagulant. Centrifuge the whole blood specimen at 2500xg for 15 minutes. Separate the plasma using a plastic pipette and place it in a plastic test tube.
    Perform the activated partial thromboplastin time assay within 4 hours.
  2. Add 1ml distilled water to vail mix well and allow it tostand for 15 minutes at ambient temperature to ensure
    it dissolved completely.
  3.  Allow the PTT reagent to reach room temperature before use.
a) Manual method
  1. Bring all reagents, controls and sample to room temperature 15 minutes prior to testing.
  2. Pipette 50 µl of PTT reagent to each tube.
  3. Pipette 50 µl of sample, controls to the tubes prepared in step 2.
  4. Incubate for 3 minutes at 37°C.
  5. Add 25µl of CaCl2 solution to each tube, start the stop watch, mix in a water bath (37°C) for 20 seconds, then record the time required for clot formation.
b) Automated Method

To perform this test, refer to the appropriate Instrument Operator’s Manual for detailed instructions.



  • Normal control sample(s): 26-36 seconds;
  • For best results, each laboratory should determine a reference range for its particular population and instrument reagent system.
    Storage and Stability:
  • PTT Reagent can be stored at 2-8°Cfor30daysafter opening.
  •  PTT Reagent should not be frozen and thawed.
  • Do not mix or use the components of thiskitwiththe components of any other kit with different lot numbers. 
  • Throughout testing all test tubes, syringes and pipettes should be plastic. 
  • Throughout testing all test tubes, incubation time should keep in constant and incubation temperature should keep at 36.5-37.5°C.
  •  Each laboratory should establish a Quality Control program that includes both normal and abnormal control plasmas to evaluate instrument, reagent tested daily prior to performing tests on patient plasmas. Monthly quality control charts are recommended to determine the mean standard deviation of each of the daily control plasma. All assays should include controls, and if any of the controls are outside the established reference ranges, then the assay should be considered invalid and no patient results should be reported. 
  • Turbid solution of CaCl2 may be indicative of product deterioration.