Activated Protein C Resistance

Coagulation is the process through which blood changes from a liquid to a gel-like state. Without this process, damaged blood vessels or wounds could continue to bleed, leading to a potential haemorrhage.

Protein C is a proenzyme that, upon activation, prevents excessive coagulation in the human body. In some cases, individuals gain resistance to activated protein C, leading to an increased formation of blood clots. This condition is termed Activated Protein C Resistance (APCR) and can increase the risk of venous thromboembolism (formation of blood clots in the veins)

Venous thromboembolism (VTE) can cause complications such as:

• Deep vein thrombosis (blood clots in the legs or pelvic area)
• Pulmonary embolism (blood clots in the lungs; potentially fatal)

APCR commonly occurs due to inherited genetic mutations in Factor V (FV) protein in the body's coagulation system. This specific mutation, dubbed the FV Leiden (FVL), creates a deficiency of the FV protein and results in an individual's predisposition toward thrombosis.

APCR can also occur independently of the FVL mutation. Some other common causes include:

• Increased levels of prothrombin (Protein that helps coagulate blood)
• Presence of lupus anticoagulants (antibodies that increase coagulation)
• Excessive use of oral contraceptives
• Rare complications during pregnancy

The condition is uniquely dangerous for infants and can lead to purpura fulminans, turning fatal if not treated immediately. Some symptoms for the same are as follows:

• Abnormal bleeding near cuts 
• Necrosis (cell/tissue death) in the affected areas
• Widespread bruising or discolouration of the skin

An Activated Protein C Resistance Test (APCR test) is a diagnostic test that evaluates patients with recurrent or active VTE to establish the presence of APCR. Individuals with a family history of VTE can also opt for this test as a precautionary measure.

An APCR test involves combining the patient specimen in diluted FV-deficient plasma. That sample is introduced to artificial coagulant agents and then incubated through an activated partial thromboplastin time (aPTT) test.

Factors such as clotting time are a part of clinical interpretation. The aPTT ratio is then assessed with and without the added agents to determine Activated Protein C sensitivity (APCR).

The APCR test is part of a more extensive assessment process. Abnormal test ratios lead to further analysis to determine whether the cause is FVL or another factor. If the test results are inconclusive, an additional test for FVL is administered to the patient to provide a medical interpretation in that clinical context.

Individuals with asymptomatic APCR do not usually receive treatment if there are no additional risk factors for thrombosis. In some cases, minor surgery using a short-term anti-coagulating agent can be helpful.

However, patients must consider long-term oral anticoagulation therapy if additional risk factors are present or the condition is symptomatic.

Apollo 24|7 provides a comprehensive Activated Protein C Resistance Test. Through the test, doctors can identify the following:

• Possible FVL mutation in a patient
• Genetic predisposition towards thrombophilia (increased formation of blood clots)

Doctors can then prescribe the necessary treatment options through that information.
 

Medically reviewed by Dr.Soumya Bhattacharya, Haematologist, Apollo Multispeciality Hospitals, Kolkata.