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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 # |
Prothrombin Time with INR
Test Code8847
CPT Codes
85610
Preferred Specimen
1 mL frozen platelet-poor plasma in a 3.2% Sodium citrate collected in a (light blue-top) tube
Minimum Volume
Plasma: 0.5 mL
Whole blood: 4.1 mL
Pediatric whole blood: 2.4 mL
Whole blood: 4.1 mL
Pediatric whole blood: 2.4 mL
Other Acceptable Specimens
5 mL random whole blood, or 2.7 mL Pediatric whole blood collected in a 3.2% sodium citrate (light blue-top) tube
Instructions
A completely filled tube is necessary because the correct ratio of blood to citrate is critical (9:1). Mix by gentle inversion 3-4 times. Do not uncap.
Transport Temperature
Plasma: Frozen
Whole blood: Room temperature
Whole blood: Room temperature
Specimen Stability
Separated platelet-poor plasma
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 14 days
Unopened light blue-top tube
Room temperature: 48 hours
Refrigerated: Unacceptable
Frozen: Unacceptable
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 14 days
Unopened light blue-top tube
Room temperature: 48 hours
Refrigerated: Unacceptable
Frozen: Unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Improper blood to citrate ratio • High hematocrit • Improper blood collection
Methodology
Photo-Optical Clot Detection
Setup Schedule
Set up: Mon-Sat; Report available: Next day
Limitations
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.
Reference Range
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
| ≤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 |
PT
| ≤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
Clinical Significance
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.
