Test Overview

Test Methodology

Photo-optical clot determination with Factor XII deficient substrate.

Test Usage

Detection of specific coagulation factor XII 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 Test Performed

Monday - Friday, one run per day

Analytic Time

1 hour

Soft Order Code


MiChart Code

Factor 12 Assay



Factor XII Assay
Factor XII:C Assay
Factor 12 Activity
Factor 12 Assay

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Specimen Requirements

Offsite 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 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.

Rejection Criteria

Specimens will be rejected if not properly filled, clotted, grossly hemolyzed, or contaminated with heparin.


Test is not indicated if the patient is receiving heparin or direct thrombin inhibitor anticoagulation therapy.


Blue Top Tube

Normal Volume

Full 2.7mL tube or 1mL plasma aliquot

Minimum Volume

Full 1.8mL tube or 1mL plasma aliquot

Additional Information

Deficiencies have no hemorrhagic consequence. Factor XII may be increased in patients with pre-eclampsia and decreased in patients with liver disease, renal disease, and Rocky Mountain spotted fever. Congenital Factor XII deficiency has been associated with an increased incidence of venous thrombosis.

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