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Activated PTT
MessagePerforming Lab: Central Lab, Hudson, Lakeview, Regions, Westfields
Test Code
3553
Alias/See Also
Sunquest: APTT; Activated Partial Thromboplastin Time, APTT, Partial Thromboplastin Time, PTT
CPT Codes
85730
Preferred Specimen
2.7 mL (in 3 mL tube) 3.2% Sodium Citrate Plasma (light blue-top) tube filled to fill line on the tube
Minimum Volume
1.0 mL
Other Acceptable Specimens
1.0 mL platelet poor plasma (Frozen)
Instructions
Collection: Samples with a hematocrit > 55% require a special anticoagulant adjusted tube for high hematocrits.
Processing: Freeze an aliquot of double-centriguged plasma (see instructions below) at -20°C if not performed within 4 hours of collection.
Shipping: HP Clinics Only: If patient is on heparin, sample should be sent to Regions Hospital for testing.
This procedure provides general instructions for double spinning,
which will produce platelet free plasma.
Check tubes for clots. Ensure adequate fill-volumes for all tubes.
1. Immediately centrifuge all specimens at 1,500 xG for 15 minutes.
2. Carefully remove plasma from cells, avoiding the platelet/buffy
coat.
3. Dispense plasma from all tubes into a single plastic tube using a
plastic transfer pipette. Do not pour off
4. Centrifuge the plasma in the plastic tube at 1,500 xG for 15
minutes.
5. Remove the top portion of plasma leaving approximately 250 µL in
the bottom to discard.
6. The double-centrifuged plasma should be aliquoted: 1 mL per
aliquot into clearly labeled plastic, polypropylene, tubes.
7. After centrifugation, examine the plasma for fibrin clots and the
RBC portion for small red cell clots. Clotted specimens must be
discarded and recollected.
8. Specimens should be frozen immediately and sent to Regions with
the routine courier on dry ice. It is important that samples remain frozen
throughout transport
Processing: Freeze an aliquot of double-centriguged plasma (see instructions below) at -20°C if not performed within 4 hours of collection.
Shipping: HP Clinics Only: If patient is on heparin, sample should be sent to Regions Hospital for testing.
This procedure provides general instructions for double spinning,
which will produce platelet free plasma.
Check tubes for clots. Ensure adequate fill-volumes for all tubes.
1. Immediately centrifuge all specimens at 1,500 xG for 15 minutes.
2. Carefully remove plasma from cells, avoiding the platelet/buffy
coat.
3. Dispense plasma from all tubes into a single plastic tube using a
plastic transfer pipette. Do not pour off
4. Centrifuge the plasma in the plastic tube at 1,500 xG for 15
minutes.
5. Remove the top portion of plasma leaving approximately 250 µL in
the bottom to discard.
6. The double-centrifuged plasma should be aliquoted: 1 mL per
aliquot into clearly labeled plastic, polypropylene, tubes.
7. After centrifugation, examine the plasma for fibrin clots and the
RBC portion for small red cell clots. Clotted specimens must be
discarded and recollected.
8. Specimens should be frozen immediately and sent to Regions with
the routine courier on dry ice. It is important that samples remain frozen
throughout transport
Transport Temperature
Room Temperature or Frozen if > 4 hours old
Specimen Stability
Patient Not on Heparin Therapy: Room Temperature: 4 hours Refrigerated: 4 hours Frozen (-20C): 72 hours Frozen (-80C): 2 Weeks
Patient on Heparin Therapy: Room Temperature: 4 hours Refrigerated: 4 hours Frozen(-20C): 72 hours Frozen (-80C): 2 Weeks
Patient on Heparin Therapy: Room Temperature: 4 hours Refrigerated: 4 hours Frozen(-20C): 72 hours Frozen (-80C): 2 Weeks
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolyzed or Clotted Samples, Samples do not meet the minimum draw requirements, Samples exceed maximum draw requirements, Samples with hematocrit >55% not collected with the special tube.
Methodology
Electromagnetic Clot Detection
Setup Schedule
Daily
Report Available
Same day.
Limitations
The effects of heparin become unapparent after medications have been discontinued for 48 hours. The PTT is not used to monitor patients on Low Molecular Weight Heparin. The appropriate test to order is an “Anti-Xa factor assay”. Patients may be on both Low Molecular Weight Heparin and Coumadin. The “INR” is the appropriate test to order for these patients.
If the patient’s hematocrit is greater than 55%, special tubes with less anticoagulant must be used for specimen collection.
If the patient’s hematocrit is greater than 55%, special tubes with less anticoagulant must be used for specimen collection.
Reference Range
24.0 - 37.0 seconds (Lakeview Only: 23.3 - 31.9 seconds)
Critical: >= 140.0 seconds
Critical: >= 140.0 seconds
Clinical Significance
A prolonged APTT with a normal PT may indicate a factor VIII, IX, XI, or XII congenital deficiency. An abnormal APTT may be observed with liver disease, consumptive coagulopathy, circulating anticoagulants (antiprothrombinase or circulating anticoagulant against a factor), during heparin or oral anticoagulant therapy, and treatments with thrombin inhibitors.
