Indicator Explainer
Activated Partial Thromboplastin Time
A measurement of the length of time that it takes for clotting to occur when activating reagents are added to a plasma specimen. The test is partial due to the absence of tissue factor (Factor III) from the reaction mixture.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C38462. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-19. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also Known As
Related Tests
Tests that measure or involve this indicator.
References
- NCI Thesaurus 26.09d — Activated Partial Thromboplastin Time (C38462)
- Source: National Cancer Institute, NCI Thesaurus 26.09d, C38462. NCI definition, reproduced without modification under CC BY 4.0.
- Conventional Prothrombin Time and Activated Partial Thromboplastin Time Mask Citrate-Induced Divalent Cation Depletion During Frozen Plasma Transfusion. — Anesth Analg, 2026-09-30 (PMID 42805188; literature)