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Catalog ID APTT Activated Partial Thomboplastin Time

CPOE Test Name




Specimen Type


Specimen Requirements

Light Blue Top (Sodium Citrate) tube; 2.7 mL blood

Storage and Transport

Room temperature. Transport to the lab immediately.

Special Instructions

Always allow blue top/citrate tubes to fill completely.

Causes for Rejection

Tube improperly filled especially underfilling;

Specimen clotted;


Reference Range

28.0 – 35.7 sec (May vary with lot number changes) Therapeutic range 58.0 – 96.0 seconds.

Critical Values

> 100 seconds

Turn Around Time

1 hour

Performing Lab

Core Laboratory AD 3301 721-2120





Testing Guidelines

The following are guidelines, and each patient's unique circumstances should be evaluated, and if needed, the following modified as deemed appropriate by the clinical team. Therapeutic monitoring may be needed on certain patient populations receiving anti-coagulation therapy. PT/INR is available within our core lab for patients on vitamin K antagonists (e.g. warfarin). UF-Hep (anti-Xa) is available within our core lab for patients on heparin drip; please follow nomogram in PowerChart. If results exceed 2 IU/mL, patients need to be monitored via aPTT as the presence of a direct Xa inhibitor is possible. Please follow nomogram in PowerChart. Monitoring may also be needed for certain patient populations on LMW heparin including patients with renal insufficiency, pregnant patients, newborns, and markedly obese or underweight patients. Most patients on direct thrombin inhibitors and anti-Xa inhibitors do not need routine monitoring. However, testing at our reference laboratory is available for certain patients on direct thrombin inhibitors and direct Xa inhibitors. Please note anticoagulation therapy may interfere with coagulation testing. Please contact the medical director of hematology if there are any questions regarding appropriate test utilization.