The Protein S test measures Protein S, a natural anticoagulant, to assess the risk of blood clotting disorders.

1. Low Protein S Levels

• Inherited deficiency: Increased risk of deep vein thrombosis (DVT) or pulmonary embolism (PE).

• Acquired deficiency: Liver disease, vitamin K deficiency, pregnancy, or certain medications.

2. Normal Levels

• Indicates proper clot regulation.

Often done with other clotting tests for a full evaluation.

Severe dehydration, Malnutrition, Kidney disease, Liver disease.

Normal Range

• General Reference Range (may vary by lab and method):

  • Total Protein S: 60-150% activity of normal value
  • Free Protein S: 65-140% activity of normal value

  Note: Values may differ slightly depending on age, gender, and specific laboratory protocols.

Interpretation of Results

• Low Protein S Levels:

  • Type I Deficiency: Reduced total and free Protein S levels (quantitative deficiency)

  • Type II Deficiency: Normal levels but reduced activity (functional deficiency)

  • Type III Deficiency: Normal total Protein S but reduced free Protein S

  • Possible Causes of Deficiency:

    • Hereditary Protein S deficiency (autosomal dominant)
    • Acquired conditions such as liver disease, vitamin K deficiency, or certain autoimmune disorders

• Normal Protein S Levels:

  • Likely no significant risk of thrombophilia due to Protein S deficiency.
  • Does not exclude other causes of clotting abnormalities.

Sample Type

• Specimen Required:
  • Blood sample (plasma)
  • Collected via venipuncture into a citrate tube (blue-top tube to prevent clotting).