Protein C and Protein S
Other names: Protein S Free (Functional) or Antigen (Total); Protein C Functional or Antigen
Proteins C and S play an important role in the regulation of the rate of blood clotting; blood clotting is brought about by the activation of the coagulation cascade, which is a process that involves the activation of more than 20 different types of protein. Thrombin is a clotting factor, which helps to control the rate of clot formation; it forms a feedback loop, which contains proteins C and S to regulate and slow down the coagulation cascade.
Problems with protein S and C may either be inherited or acquired; there are two types of protein C deficiencies and 3 types of protein S deficiencies.
When is the test used?
The test may be used to assess the quantity or activity of protein C and S; the test is commonly used to investigate the cause of a venous thromboembolism (especially if the patient is younger than 50 or the clot has developed in an unusual place). Tests may also be used to assess factor activity; this test will usually be carried out alongside a number of other tests.
The test is usually ordered when a patient has had a thrombotic episode; the test should be done a minimum of ten days after the episode and the test should not be done while the patient is on anticoagulant therapy. Other tests may be carried out to see if the patient has another health condition, which may be affecting blood clotting.
The test may also be used after a thrombotic episode to determine the risk of the patient suffering another episode.
How is the test performed?
The test is done by collecting and analysing a sample of the patient’s blood; a needle is inserted into the vein (usually on the inside of the elbow) and the blood is collected in a syringe. When the doctor (or nurse) has a sufficient sample, the blood will be bottled, labelled and sent to the laboratory for testing.
What do the test results show?
If the test results are normal, this usually indicates that the clotting process is working effectively.
If levels of protein C and S are higher than normal, this is not normally a cause for concern as long and the results show that the proteins are functional and that the protein S is free. If the results show that the protein is not functioning normally, further tests will usually be ordered and the patient’s condition will be monitored closely.
Decreased levels of protein C and S may be caused by a number of health conditions, including:
- Liver disease
- Kidney disease
- Severe infections
- Vitamin K deficiency
- Certain forms of cancer
- HIV
- Inflammatory conditions
Levels may also decrease during pregnancy or if the patient is receiving heparin anticoagulant therapy.
Specific Blood Tests
- Specific Blood Tests
- Factor V Leiden Mutation and PT 20210 Mutation
- Ferritin Test
- Fibrinogen
- Fructosamine
- FSH Test
- G6PD
- Gastrin
- GGT
- Glucose test
- Growth hormone
- Haemoglobin
- Haptoglobin
- HbA1c test
- HDL Cholesterol Test
- Helicobacter Pylori test
- Heparin Anti-Xa
- Hepatitis A Virus
- Hepatitis B Virus
- Hepatitis C Virus
- Her-2/neu Testing
- Heterophil Antibody Titre
- High-Sensitivity C-Reactive Protein
- HIV Antibody Test
- HIV Resistance Testing
- HIV Viral Load
- IGF-1
- Immunoreactive Trypsin
- Insulin
- Iron test
- LDH
- LDL Cholesterol Test
- Lead Test
- LH Test
- Lipase Test
- Lipoprotein (a)
- Lithium
- Lupus Anticoagulant
- Lyme disease test
- Maternal screening
- Mercury, Urine and Blood
- Mycophenolic Acid
- Myoglobin Test
- Oestrogen
- Osmolality
- Overdose Drug Test
- Paracetamol
- Parathyroid Hormone
- Parvovirus B19
- PCV
- Pertussis
- Phenobarbital
- Phenytoin
- Phospate
- Platelet Count
- Porphyrins
- Potassium Test
- Prealbumin Test
- Procalcitonin
- Progesterone Test
- Prolactin
- Prostate-Specific Antigen
- Protein 24 Capsid Antigen
- Protein C and Protein S
- Protein Electrophoresis Immunofixation Electrophoresis
- Prothrombin Time
- PSEN1 Test
- PTH
- Reticulocyte count
- Rheumatoid factor
- Rubella test
- Salicylic Acid
- Serotonin
- Sex Hormone Binding Globulin
- Sickle Cell Test
- Sirolimus
- Smooth Muscle Antibody
- Sodium Test
- Soluble Mesothelin-Related Peptides
- Synacthen Test
- Syphilis Test
- Tacrolimus
- Tau protein
- Testosterone Test
- Theophylline & Caffeine
- Thiopurine s-methyltransferase
- Thyroglobulin (Tg)
- Thyroid peroxidase antibody (TPOAb)
- Thyroid-Stimulating Hormone
- Thyroxine
- TIBC, UIBC & Transferring
- TORCH Test
- Total Protein test
- Triiodothyronine
- Triglycerides Test
- Troponin test
- Urea test
- Uric Acid
- Valproic Acid
- Vancomycin
- Very Low Density Lipoprotein
- Vitamin B12 and Folate
- Vitamin D
- West Nile Virus
- White blood cell differential count
- Zinc Protoporphyrin
- Activated Clotting Time
- ACTH
- Albumin
- Aldosterone and Renin
- Alkaline Phosphatase Test
- Allergen-Specific IgE Antibody Test
- Alpha-1 Antitrypsin
- Alpha-Fetoprotein
- ALT
- AMA
- Ammonia
- Amylase Test
- Angiotensin Converting Enzyme
- Antinuclear Antibody
- Antithrombin
- Apolipoprotein A-I
- Apolipoprotein E Genotyping
- aPTT
- AST
- Bicarbonate
- Bilirubin
- Blood cultures
- Blood film
- Blood Gas Tests
- Blood Ketones
- Brain Natriuretic Peptide
- BRCA-1 & BRCA-2
- CA 125
- Cancer Antigen 15-3
- Cancer Antigen 19-9
- C-peptide
- Caeruloplasmin
- Calcitonin
- Calcium Test
- Carbamazepine
- Cardiac Risk Assessment
- Cardiolipin Antobodies
- Catecholamines, Plasma and Urine
- CCP
- CD4 and CD8
- CEA Test
- CF Gene Mutation Testing
- Chickenpox and Shingles Tests
- Chloride Test
- Cholesterol Test
- Chlorinesterase Test
- Chromogranin A
- Ciclosporin
- CMV
- Coagulation Factors
- Coeliac Disease Tests
- Copper
- Cortisol Test
- Creatine Kinase CK-MB Test
- Creatine Kinase Test
- Creatinine
- Creatinine Clearance
- C-Reactive Protein
- Cystatin C
- D-Dimer
- DHEAS
- Digoxin
- Direct LDL cholesterol
- eGFR - Calc. Creatinine Clearance
- Electrolytes
- Epstein-Barr Virus Antibodies
- Erythrocyte Sedimentation Rate
- Erythropoietin
- Ethanol
Blood Test Guide
- Blood Tests
- Types of blood tests
- what to expect
- What are the risks of blood tests?
- What do blood tests show?
- Specific Blood Tests