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Clotting; factor VIII (AHG), 1-stage

CPT4 code

Name of the Procedure:

Clotting; factor VIII (AHG), 1-stage


Factor VIII (AHG) 1-stage clotting test is a medical procedure used to evaluate the function and level of factor VIII in the blood, which is crucial for proper blood clotting.


This test addresses conditions related to abnormal bleeding or clotting, primarily hemophilia A. The goal is to measure the activity of factor VIII to diagnose bleeding disorders, monitor treatment effectiveness, and guide therapeutic decisions.


The procedure is indicated for patients exhibiting symptoms such as excessive bleeding, frequent nosebleeds, easy bruising, or prolonged bleeding from cuts. It is also appropriate for those with a family history of hemophilia or related disorders.


Patients may need to refrain from taking blood-thinning medications, such as aspirin, before the test. No special fasting or other preparations are typically required.

Procedure Description

  1. Blood Sample Collection:
    • A healthcare professional cleans the skin over the vein, usually in the arm.
    • A needle is inserted to draw a blood sample.
  2. Laboratory Analysis:
    • The blood sample is sent to a lab.
    • Factor VIII activity is measured using a 1-stage clotting assay, where the blood sample is mixed with substances that trigger clotting and the time taken for a clot to form is recorded.


The blood collection takes only a few minutes, and the lab analysis may take a few hours to a day.


The blood sample is typically collected in an outpatient clinic, hospital, or diagnostic laboratory.


A phlebotomist or nurse typically collects the blood sample. A laboratory technician or hematologist analyzes the sample.

Risks and Complications

The procedure carries minimal risks, mainly associated with blood draw, such as bruising, infection at the puncture site, or dizziness.


Accurate diagnosis and monitoring of bleeding disorders. Results from the test guide treatment plans, helping to manage and reduce the risk of bleeding episodes.


There is no recovery time needed from the blood draw, though patients might experience minor soreness at the blood draw site. Normal activities can usually be resumed immediately.


Other blood tests, such as chromogenic assays or genetic testing, can also be used to diagnose and monitor hemophilia. Each alternative has its own set of benefits and limitations in terms of accuracy, cost, and availability.

Patient Experience

The patient may feel a brief pinch or stinging sensation during blood draw, followed by minor discomfort or bruising. Generally, the procedure is quick and straightforward, with minimal pain or discomfort.

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