Prothrombin Time with INR
Test Code
8847
85610
CPT Code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.
Clinical Significance
Prothrombin Time with 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.
Test Resources
Test FAQ
Prothrombin Time with INRTest Details
Methodology
Photo-Optical Clot Detection
Reference Range(s)
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
Alternative Name(s)
PT
Collection 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.
Reject Criteria
Gross hemolysis • Grossly lipemic • Improper blood to citrate ratio • High hematocrit • Improper blood collection
Setup Schedule, Preferred Specimen(s), Alternative Specimen(s), Minimum Volume, Transport Container, Transport Temperature, Specimen Stability
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.
Mix by gentle inversion 3-4 times. Do not uncap.
Gross hemolysis • Grossly lipemic • Improper blood to citrate ratio • High hematocrit • Improper blood collection