| 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 # |
PT AND APTT
Test CodeLAB1977
Quest Code
4914
CPT Codes
85610, 85730
Preferred Specimen
One full unopened 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL frozen plasma
Other Acceptable Specimens
1 mL frozen plasma
Instructions
Unopened light blue-top tube: Correct ratio of blood to citrate is critical. Do not overfill or underfill collection tube. Mix by inversion 4 times. For non-heparinized patients, maintain specimen at room temperature. Do not uncap. Stable 24 hours at room temperature.
Platelet-poor plasma: Centrifuge light blue-top tube 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcl). Freeze immediately and ship on dry ice.
Whole blood: The tubes should be at 100% +/- 10% fill volume in order to obtain the correct ratio.
Platelet-poor plasma: Centrifuge light blue-top tube 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcl). Freeze immediately and ship on dry ice.
Whole blood: The tubes should be at 100% +/- 10% fill volume in order to obtain the correct ratio.
Transport Container
3.2% sodium citrate (light blue-top) tube
Transport Temperature
Room temperature
Specimen Stability
Unopened light blue-top tube
Room temperature: 24 hours
Refrigerated: Unacceptable
Frozen: Unacceptable
Separated platelet-poor plasma
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 14 days
Room temperature: 24 hours
Refrigerated: Unacceptable
Frozen: Unacceptable
Separated platelet-poor plasma
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 14 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Improper blood to citrate ratio • Clotted • High hematocrit • Improper blood collection
Methodology
Photo-optical Clot Detection
Limitations
PT/INR: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): little to no effect (reagent contains a heparin neutralizer); Dabigatran or Argatroban (Thrombin Inhibitors): normal to prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.
aPTT: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): prolonged; Dabigatran or Argatroban (Thrombin Inhibitors): prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.
aPTT: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): prolonged; Dabigatran or Argatroban (Thrombin Inhibitors): prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.
Reference Range
Prothrombin Time with INR
INR
PT
Flagging not provided. Pediatric reference intervals have not been established. Based on published literature, the adult reference interval (9.0-11.5 seconds) is generally applicable down to approximately 3 months of age with younger patients having a slightly higher upper limit by several seconds. Warfarin Therapeutic INR Range: 2.0-3.0
Partial Thromboplastin Time, Activated
Flagging not provided. Pediatric reference intervals have not been established. Based on published literature, the adult reference interval (23-32 seconds) is generally applicable down to approximately 6 months of age with younger patients having a slightly higher upper limit by several seconds.
INR
| ≤3 months | Not established |
| >3 months | |
| Reference range | 0.9-1.1 |
| Moderate-intensity Warfarin therapy | 2.0-3.0 |
| Higher-intensity Warfarin therapy | 3.0-4.0 |
| ≤3 months | Not established |
| >3 months | 9.0-11.5 sec |
Flagging not provided. Pediatric reference intervals have not been established. Based on published literature, the adult reference interval (9.0-11.5 seconds) is generally applicable down to approximately 3 months of age with younger patients having a slightly higher upper limit by several seconds. Warfarin Therapeutic INR Range: 2.0-3.0
Partial Thromboplastin Time, Activated
| ≤6 months | Not established |
| >6 months | 23-32 sec |
Flagging not provided. Pediatric reference intervals have not been established. Based on published literature, the adult reference interval (23-32 seconds) is generally applicable down to approximately 6 months of age with younger patients having a slightly higher upper limit by several seconds.
Clinical Significance
PT/INR: Screening test for abnormalities of coagulation factors that are involved in the extrinsic pathway. Also used to monitor effects of Warfarin therapy and to study patients with hereditary and acquired clotting disorders.
aPTT: The aPTT is a screening test that will detect deficiencies or inhibitors to the intrinsic (Factors VIII, IX, XI and XII) and common (Factors II, V, X and Fibrinogen) pathway coagulation factors.
aPTT: The aPTT is a screening test that will detect deficiencies or inhibitors to the intrinsic (Factors VIII, IX, XI and XII) and common (Factors II, V, X and Fibrinogen) pathway coagulation factors.
Performing Laboratory
| Quest Diagnostics-Lenexa |
| 10101 Renner Blvd |
| Lenexa, KS 66219-9752 |
Last Updated: August 13, 2021
