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Useful For
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For Screening of certain coagulation factor deficiencies and to monitor heparin therapy (unfractionated heparin) .
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Method name and description
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Coagulometric (Turbidimetric).
Test is performed using different analyzer platforms .
Factors of the Intrinsic Coagulation System are activated by incubating the plasma with optimal amount of phospholipids and a surface activator. The addition of calcium ion triggers the coagulation process, and the clotting time is then measured.
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Reporting name
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Activated Partial Thromboplastin Time (APTT)
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Clinical information
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Activated partial thromboplastin time (APTT) measures the integrity of the intrinsic (factors VIII, IX, XI and XII) and common (factors II, V, X, and I [fibrinogen]) pathway coagulation factors as well as contact factors, prekallikrein (PK) and high-molecular-weight kininogen (HMWK). Also, it is used to monitor patients on heparin therapy.
This test reflects the activities of the coagulation factors in the intrinsic and common procoagulant pathway, but not the extrinsic procoagulant pathway, which includes factor VII and tissue factor, nor the activity of factor XIII (fibrin stabilizing factor).
The APTT test is frequently used to monitor therapy with unfractionated heparin (UFH). Since APTT reagents can vary greatly in their sensitivity to UFH, it is important to establish a relationship between APTT response and heparin concentration.The therapeutic APTT range in seconds should correspond with a UFH concentration of 0.3 to 0.7 U/mL as assessed by a heparin assay (inhibition of factor Xa activity measured by a chromogenic assay ).
Prolongation of the activated partial thromboplastin time (APTT) can occur as a result of deficiency of one or more coagulation factors (acquired or congenital in origin), or the presence of an inhibitor of coagulation such as heparin, a lupus anticoagulant, a nonspecific inhibitor such as a monoclonal immunoglobulin, or a specific coagulation factor inhibitor.
Prolonged clotting times may also be observed in various conditions including fibrinogen deficiency, liver disease, and vitamin K deficiency, DIC.
Shortening of the APTT usually reflects either elevation of factor VIII activity in vivo that most often occurs in association with acute or chronic illness or inflammation. Shortening can also encountered in early stages of DIC caused by circulating procoagulants , or spurious results associated with difficult venipuncture and improper specimen collection.
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Specimen type / Specimen volume / Specimen container
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Plasma Na Cit. Platelet-poor plasma.
Specimen Volume: 2.7 ml.
Container/Tube: Light-blue top (citrate).
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Collection instructions / Special Precautions / Timing of collection
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- Samples collected in HMC facilities MUST reach the coagulation laboratory within 1 hour of collection.
- Samples collected in non-HMC facilities / external clients: MUST reach coagulation laboratory within 1 hour of collection, if not applicable, centrifuge the whole blood and carefully remove the plasma (by pipette not by decanting) and send it in a temperature-controlled environment (18- 25 ºC) within 2 hours of centrifugation. If the transportation of the plasma can’t be within a maximum of 2 hours, prepare platelet-poor plasma as follows:
- Re-centrifuge the plasma again.
- Remove the top portion of plasma leaving approximately 250 ul in the bottom to discard.
- The double-centrifuged plasma should be aliquoted into labeled plastic tubes.
- Freeze immediately at -20 ºC or below
- Specimens must arrive frozen.
- If patient HCT is >55%, test will not be processed. The ordering Physician will be contacted to reorder the test and call the patient to go to Phlebotomy for recollection. Instruct the patient to inform the phlebotomy about his high HCT% , the phlebotomy will contact the lab to request a coagulation tube after adjusting amount of anticoagulant.
Note:
Collection of blood for coagulation testing through intravenous lines that have been previously flushed with heparin should be avoided, if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution must be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and not used for coagulation testing. For those specimens collected from a normal saline lock (capped off venous port) twice the dead space volume of the catheter and extension set should be discarded.
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Relevant clinical information to be provided
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Patient/family history of bleeding or thrombotic disorder. History of anticoagulant therapy. History of chronic diseases.
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Storage and transport instructions
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Specimen Rejection Criteria
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Specimens with no label or missing required identification
Broken, leaking or contaminated specimen
Clotted samples
Under-filled or overfilled sample tubes.
Wrong sample container sample received
Improper specimen transport temperature (e.g. like specimens which are needed to be sent on ice)
Old specimen (test-dependent)
Grossly Hemolyzed sample (test-dependent)
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Biological reference intervals and clinical decision values
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The DLMP laboratories use a number of different platforms for this test. Please refer to the below:
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Facility
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Platform
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Reference range
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QRI, NCCCR, RRC-Lab, HMGH, AWH and ABHA
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ACL TOP
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Age
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Reference interval(sec)
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0 Minutes-4 Days
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31.3-54.5
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4 Days-1 Months
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25.4-59.8
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1 Months-6 Months
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24.8-40.7
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6 Months-1 Years
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25.1-40.7
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1 Years-5 Years
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24.0-39.2
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5 Years-10 Years
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26.9-38.7
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10 Years-17 Years
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24.6-38.4
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>17 Years
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25.1- 36.5
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Heparin therapeutic range: 76-104 seconds.
For pediatric population up to 17 years old, the reference range is quoted from literature. The reference range values have not been verified/established by Lab.
*For Pediatric population up to 1 month, the reference range is quoted from Andrew et al.: Development of the hemostatic system in the neonate and young infant. Am J Pediatric Hematology Oncology 1990; 12:95)
* For Pediatric population up to 17 years old, the reference range is quoted from Pierre Toulon et al: Age dependency for coagulation parameters in paediatric populations Results of a multicentre study aimed at defining the age-specific reference ranges, Thrombo Hemost ,2016,Coagulation and Fibrinolysis:116:9-16.
*For >17 years old, the reference range is quoted from Reagent instructions for use (IFU) provided by manufacture and verified by the lab.
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AKH and Cuban
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Sysmex
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Age
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Reference interval(sec)
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0 Minutes-4 Days
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31.3-54.5
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4 Days-1 Months
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25.4-59.8
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1 Months-6 Months
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21-33
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6 Months-1 Years
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24-33
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1 Years-5 Years
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24-30
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5 Years-10 Years
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25-32
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10 Years-18 Years
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25-30
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> 18 Years
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24.6-31.2
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Heparin therapeutic range: 50-70 seconds.
For pediatric population up to 18 years old, the reference range is
quoted from literature. The reference range values have not been verified/established by Lab.
*For Pediatric population up to 1 month, the reference range is quoted from Andrew et al.: Development of the hemostatic system in the neonate and young infant. Am J Pediatric Hematology Oncology 1990; 12:95)
*For Pediatric population up to 18 years old, the reference range is quoted from APPEL I. M. , GRIMMINCK B, GEERTS J ,. STIGTER R , et al: Age dependency of coagulation parameters during childhood and puberty. Journal of Thrombosis and hemostasis, August-2012,10:2254-2263.
*For >18 years old, the reference range is quoted from SYSMEX CS‑ System Reference Guide and verified by the lab.
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For patients on direct oral anticoagulant medications (non-vitamin K), APTT should not be used for monitoring anticoagulation because the effect of this test is not predictable.
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Factors affecting test performance and result interpretation
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No interference up to
Triglycerides 11.3 mmol/L
Hemoglobin 0.5 g/dL
Bilirubin 444.6 umol/L
Vary according to the platform used for processing the test.
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Turnaround time / Days and times test performed / Specimen retention time
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Stat:1 hr.
Routine:4 hrs. / Daily / NA
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