Sign in →

Epic Code LAB325 APTT

Important Note

Specimens collected from patients receiving heparin therapy must be centrifuged within 1 hour and the plasma removed and frozen, if not test should be run immediately.

Specimen tube must be full.

There is currently a nationwide shortage of this tube. Please take steps to ensure specimen integrity to reduce recollection. Specimen Tube Shortage (link)

Test Name Alias

Activated Partial Thromboplastin Time | PTT | 8450

Interface Order Alias


Quick Collect


Clinical Information

The activated partial thromboplastin time is a measurement of the activity of the factors involved in the intrinsic and common pathways of coagulation. The APTT is also used to monitor unfractionated heparin therapy.  Prolonged APTT may occur in the following:  Inherited factor deficiencies, anticoagulant therapy, vitamin K deficiency, liver disease, circulating anticoagulants, lupus inhibitors, factor inhibitors, or consumption of fibrinogen or other coagulation factors in DIC.

Collection Instructions

Specimen Collection: Blood


Container(s): 3.2% Na Citrate Tube (blue top)

Preferred Volume to Collect: 2.7 mL (full tube)

Minimum Volume to Collect: 1.8 mL (full tube)

Capillary collect ok: No

Microtainer acceptable: No


Collection Instructions:

  • Detailed instructions (link): Anticoagulant Correction for High Hematocrit

  • Detailed instructions (link): Blue Citrate Tube

  • Specimen should be processed within 4 hours – See Processing Instructions below.
    • Specimens collected from patients receiving heparin therapy must be processed within 1 hour – See Processing Instructions below.

Processing Instructions (Laboratory, Outpatient or Off-site collection)

Processed Specimen: Platelet Poor Plasma


Centrifuge/Spin: Yes

Aliquot: Yes


Processing Instructions:

  • Detailed instructions (link): Preparing Platelet Poor Plasma
  • Separate plasma into 1 – 2 aliquots, minimum of 0.5 mL each.
  • Freeze aliquots in plastic transport tubes immediately.

Transport Temperature:

  • Ambient (up to 4 hours in whole blood state, 1 hour for patients on heparin therapy)
  • Frozen (plasma only >4 hours)

Rejection Criteria

  • Hemolysis
  • Specimen has been thawed

Specimen Stability

Ambient: up to 4 hours in whole blood state if the patient is not on heparin

Refrigerate: Not Acceptable

Frozen: Aliquot and freeze platelet poor plasma within 1 hour of collection if the patient is on heparin. Also freeze if >4 hours post collection plasma.

Laboratory Retention: 24 hours

Test Frequency

Available 24 hours, usual TAT 1 day.

Reference Range

Effective September 26, 2023, at 9:00 AM

  • 24 – 34 seconds (CS series analyzers including Corewell Health Reference Lab, Grand Rapids; Corewell Health West Regional Hospital Labs at Blodgett, Big Rapids, Gerber, Kelsey, Ludington, Pennock, Reed City, United and Zeeland)

  • 23 – 28 seconds (Corewell Health Reference Lab, Grand Rapids, BCS series analyzers)

Laboratory Critical Values Table

Performing Department


Performing Department Laboratory Location

Corewell Health Reference Laboratory, Grand Rapids, MI

Corewell Health Laboratories West:
Corewell Health Big Rapids Laboratory, Big Rapids, MI
Corewell Health Blodgett Laboratory, Grand Rapids, MI
Corewell Health Gerber Laboratory, Fremont, MI
Corewell Health Kelsey Laboratory, Lakeview, MI
Corewell Health Ludington Laboratory, Ludington, MI
Corewell Health Pennock Laboratory, Hastings, MI
Corewell Health Reed City Laboratory, Reed City, MI
Corewell Health Greenville Laboratory, Greenville, MI
Corewell Health Zeeland Laboratory, Zeeland, MI


Clot-based assay



CDM Code


Epic Test ID



APTT: 14979-9

Mayo Access Code


Reviewed Date


Last Update

9/26/2023, 09:00: Reference Range