Included in Coagulation Panel.

ACTIVATED PARTIAL THROMBOPLASTIN TIME (LAB325)

Draw 1 FULL Blue top tube, sterile siliconized interior, buffered 3.2% sodium citrate, blood: anticoagulant volume 9:1.

Invert the tube gently three or four times immediately after venipuncture to ensure proper mixing of blood and anticoagulant. An evacuated tube system or syringe may be used. If an evacuated tube system is used, the coagulation sample should be the second or third tube collected. If blood is drawn from an indwelling catheter, the line should be flushed with saline and the first 5 mL of blood discarded or used for other laboratory tests. Please contact Aspirus Reference Laboratory or refer to CLSI document H21-A5 for further details.

Proper labeling of the tube requires patient last name, first name, medical record number, DOB, phlebotomist initials, and date/time of collection. The information on the tube must correlate with the written requisition (either computer label or test requisition).

Refer to Storage/Transport Temperature section.

If greater than a 4-hour delay in testing OR if a facility is sending testing to another laboratory, then
Separate plasma from cells immediately or within 1 hour of collection.

Volume Requirement: Preferred: 1.0 mL platelet-poor citrate plasma (minimum: 0.5 mL)

PTT (Activated Partial Thromboplastin Time) for NON-heparinized patients:

• If the testing is completed within 4 hours from time of specimen collection, then the blue top tube can be maintained uncentrifuged or centrifuged with plasma remaining on top of the cellular component, in an unopened tube, at room temperature (18-24ºC) for up to 4 hours from time of specimen collection.
  • For whole blood samples maintained at room temperature, avoid mechanical agitation during storage.
  • Sample integrity at room temperature is enhanced if samples are centrifuged immediately after blood collection.
• If the testing is not completed within 4 hours for PTT for NON-heparinized patients specimens from time of collection, then platelet-poor-plasma should be removed immediately or within 1 hour of collection without disturbing the sedimented cells (buffy coat) and frozen at -20°C or below for short-term storage (up to 2 weeks) or -70ºC or below for long-term storage. 
• Refer to your Sites SOP (Standard Operating Procedure) for instructions on How to prepare platelet-poor plasma (platelet count <10,000 /uL)(<10 X 10⁹/L).

PTT (Activated Partial Thromboplastin Time) for SUSPECTED patients on UNFRACTIONATED HEPARIN Specimens:

• Centrifuge within 1 hour from time of specimen collection, plasma may remain on the packed cells and the plasma tested within 2 hours from time of specimen collection, at room temperature (18-24ºC).  If agitation of the specimen is likely after centrifugation, such as transportation to a remote testing site, then the platelet-poor plasma should be removed within 1 hour of collection, and frozen at -20°C or below for short-term storage (up to 2 weeks) or -70ºC or below for long-term storage. 
• Refer to your Sites SOP (Standard Operating Procedure) for instructions on How to prepare platelet-poor plasma (platelet count <10,000 /uL)(<10 X 10⁹/L).

Visually inspect the tubes. Specimens are to be rejected if:

1. Not properly labeled.
2. Collected in wrong tube type. No other anticoagulant is acceptable.
3. Short-draws (tubes less than 90% full).
4. Over-draws.
5. Hemolyzed (hemolyzed specimens should not be used because of possible factor activation (PT and APTT may be shorter) and possible end point interference).
6. Clotted (the whole blood specimen is checked for clots by gentle inversion).
7. Hematocrit > 55%, specimen must be recollected using a lesser amount of sodium citrate anticoagulant that is determined by the hematocrit of the patient. Refer to REMARKS section.
8. Suspected serum samples showing prolonged PT, PTT and very low fibrinogen levels may be confirmed as serum by a calcium determination within normal range.
9. Specimen is stored at refrigerated temperatures (2-8ºC).
10. Lipemia and icterus does not interfere with the mechanical endpoint detector of the Stago analyzers when measuring clot-based tests (PT,aPTT, TT, Fib). Cloudy plasmas may produce under-estimation of D-Dimer level Refer to Aspirus Reference Laboratory Department for D-Dimer procedure.
11. Specimens at room temperature for greater than 4 hours. 
12. Non-frozen specimen when testing is greater than 4 hours from collection.

Unopened, uncentrifuged OR centrifuged tube (plasma on packed cells): Ambient: 4 hours.

After plasma separation from cells (aliquoted platelet-poor citrate plasma): Frozen: (-20°C) 2 weeks; Frozen: (-70°C) 6 months

The citrate concentration must be adjusted in patients who have hematocrit values above 55% prior to collection. 

Contact Aspirus Reference Laboratory (715-847-2136), Coagulation Department, for assistance in obtaining a sodium citrate corrected collection tube and collection instructions prior to collecting specimen for coagulation testing.

APTT:  23 - 36 seconds    Effective date: 8/1/2018

Therapeutic range for APTT:  74 - 115 seconds (equivalent to 0.3-0.7 IU/mL anti-Xa heparin)    
Effective date: 8/1/2018

Critical aPTT results is >145 seconds

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