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| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
ACTIVATED PARTIAL THROMBOPLASTIN TIME
Test CodeAPTT
Alias/See Also
aPTT
CPT Codes
85730
Preferred Specimen
Blue Tube (Sodium Citrate)
If a butterfly needle is use for collection, a NON-ADDITIVE discard tube must be drawn first
If a butterfly needle is use for collection, a NON-ADDITIVE discard tube must be drawn first
Patient Preparation
None
Minimum Volume
1 mL (Tube MUST be filled to nominal line for proper whole blood to anticoagulant ratio – see volume guides below)
Instructions
Upon collection, gently mix by inversion 6 times.
Lab note: Refer to document below (Obtaining a Platelet-Poor Specimen)
Lab note: Refer to document below (Obtaining a Platelet-Poor Specimen)
Transport Container
BLUE Tube
Transport Temperature
Room Temperature
Specimen Stability
- 15-25ºC (room temperature) whole blood up to 24 hours
- -20ºC (frozen) plasma samples are stable
Methodology
- Hemolyzed
- Clotted
- Sample tube underfilled or overfilled
Setup Schedule
DAILY, as received
Report Available
STAT: <60 minutes
Routine: <4 hours
Routine: <4 hours
Reference Range
Male/Female All Ages: Normal Range: 22.9-36.3 SEC Critical High : >=100.1 SEC
Coagulation Therapy Effects on aPTT Assays
It has been well noted that intervening coagulant therapeutics have some effect on aPTT assays. Emicizumab, the new drug treatment for hemophilia A, can also be added to this growing list of drugs. Emicizumab will falsely decrease the aPTT clotting time, giving the potential for a false normal value in a hemophilia A patient. For patients taking emicizumab, aPTT results may not be accurate for up to six months after discontinuation of the medication. Along with emicizumab, there are several other coagulation therapeutics that may influence the aPTT assay. Below is a table of commonly used therapies and their effects on the aPTT assay.
Coagulation Therapy Effects on aPTT Assays
It has been well noted that intervening coagulant therapeutics have some effect on aPTT assays. Emicizumab, the new drug treatment for hemophilia A, can also be added to this growing list of drugs. Emicizumab will falsely decrease the aPTT clotting time, giving the potential for a false normal value in a hemophilia A patient. For patients taking emicizumab, aPTT results may not be accurate for up to six months after discontinuation of the medication. Along with emicizumab, there are several other coagulation therapeutics that may influence the aPTT assay. Below is a table of commonly used therapies and their effects on the aPTT assay.
| Drug Name | Effect on aPPT |
| Emicizumab | Decreases aPTT (potential for false normal value) |
| Unfractionated Heparin | Increases aPTT |
| LMW Heparins | May potentially increase aPTT |
| Fondaparinux | May potentially increase aPTT |
| Argatroban | Increases aPTT |
| Dabigatran | Increases aPTT |
| Rivaroxaban | May potentially increase aPTT |
| Apixaban | May potentially increase aPTT |
| Warfarin | May potentially increase aPTT (weak effect) |
Clinical Significance
Coag screen for plasma-clotting factors, not factors VII and XIII; screen for defects of the extrinsic and common coagulation pathways.
Performing Laboratory
Mount Sinai Hospital
Holy Cross Hospital
Additional Information
BD Vacutainer Blue Top Volume Guide
Greiner Vacutainer Blue Top Volume Guide
Obtaining A Platelet-Poor Specimen
