Test Overview
Test Methodology

Photo-optical clot determination with Factor XI deficient substrate.

Test Usage

Detection of specific coagulation factor XI deficiency

Reference Range *

50-150% of normal activity.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Details
Days Set Up
Daily, 24 hours for UMHS inpatients, Emergency Department patients, and Veterans Hospital patients. Monday-Friday, 1 run per day for MLabs and outpatients.
Analytic Time

2 hours

Soft Order Code
MiChart Code
Factor 11 Assay
  • Factor 11 Activity
  • Factor XI Assay
  • Factor XI:C Assay
  • F11
  • Factor 11 Assay
STAT Availability

STAT requests for this request will be performed for UMHS inpatients, Emergency Department patients, and Veterans Hospital patients.

Specimen Requirements
Collection Instructions

Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a polypropylene plastic vial, and freeze the specimen within 4 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Test is not indicated if the patient is receiving heparin or direct thrombin inhibitor anticoagulation therapy.
Normal Volume
Full 2.7mL tube or 1mL plasma aliquot
Minimum Volume
Full 1.8mL tube or 1mL plasma aliquot
Storage Temperature
Room temperature for whole blood or frozen aliquot of citrated plasma.
Rejection Criteria
Specimens will be rejected if not properly filled, clotted, grossly hemolyzed, or contaminated with heparin.
Additional Information

Factor XI normally increases during pregnancy. Decreased factor XI may be associated with: factor XI deficiency, nephrotic syndrome, pre-eclampsia, and Noonan's syndrome.

CPT Code
Fee Code