Blood Proteins and Clinical Importance

Blood Proteins and Their Clinical Importance

• Learning Objectives:
  • List blood proteins.
  • Explain the difference between plasma and serum.
  • Describe the properties of blood collection tubes.
  • Relate blood protein levels to clinical tables.

Blood Composition

• Blood is composed of:
  • Plasma (about 55%): Water, proteins, electrolytes
  • Platelets (0.01%): Involved in blood clotting
  • Red blood cells (about 41%): Carry oxygen
  • White blood cells (about 4%): Lymphocytes, Basophils, Eosinophils, Monocytes, Neutrophils (Immune response)

Plasma Proteins

• Albumin: Produced by the liver; transport protein for various substances (Ca2+, Na+, K+, bilirubin, fatty acids, hormones, and xenobiotics).
• Globulins: Associated with transport (alpha and beta globulins – lipids and fat soluble vitamins), immune response (complement and gamma globulins – antibodies).
• Fibrinogen: Essential for blood clotting.
• Other proteins: Clotting factors, hormones, enzymes, etc.

Blood Collection Tubes

• Red-top tubes: No additives; for serum collection in chemistry tests.
• Purple/Lavender-top tubes: Contain EDTA; for complete blood count (CBC) and blood typing.
• Green-top tubes: Contain heparin; for plasma collection.
• Blue-top tubes: Contain sodium citrate; for coagulation studies (PT, APTT).
• Yellow-top tubes: Contain clot activator and gel separator; for serum tests and biochemistry.
• Gray-top tubes: Contain fluoride/oxalate; for glucose and lactate testing.

Plasma and Serum

• Plasma: Obtained by centrifuging anticoagulated blood; contains clotting factors. Used for coagulation, blood transfusions and diagnostic tests like antibody and hormone assays.
• Serum: Obtained after blood is allowed to clot and centrifuged; lacks clotting factors. Used for antibody and hormone assays.

Clinical Significance of Blood Proteins

• Hyperproteinemia: More protein in the blood. Can be from dehydration, polyuria or inadequate fluid intake; diabetes, or inflammatory conditions
• Hypoproteinemia: Less protein in the blood. Can be from water intoxication, heart failure, excessive protein loss or protein synthesis problems.
• Plasma protein levels: Normal range is 6-8 g/dL. Used to diagnose diseases.

Clinical Biomarkers (Enzymes)

• Enzymes: Tissue-specific; enzyme presence and activity in the blood often associated with diseases affecting specific organ or tissues.
• Diagnostic Enzymology: Used to assess tissue damage, including heart and lung disease, liver disease, muscle disease, bone disease, pancreatic disease, malignancies, genetic diseases, hematological diseases and poisoning.
• Serum Enzymes:
  • Transaminases (AST, ALT)
  • Lactate dehydrogenase (LDH)
  • Creatine kinase (CK)
  • Alkaline phosphatase (AP)
  • Amylase (AMS)
  • Lipase (LPS)

Clinical Biomarkers Analysis

• Fresh blood or serum samples are required for accurate analysis.
• Maintaining proper storage temperatures (+4°C), necessary for preventing enzyme inactivation.
• Proper blood collection technique or anticoagulant/no anticoagulant usage is crucial for tests in the lab.

Genetic Disorders Diagnosis

• Genetic disorders such as phenylketonuria, galactosemia, galactose-1-phosphate, uridylyltransferase, glucose homeostasis and glucose 6-phosphatase are diagnosed in the laboratory.
• These disorders involve enzyme deficiencies in the body leading to accumulation of harmful metabolic compounds.

Diagnosis of Poisoning

• Serum cholinesterase tests performed to diagnose poisoning with organic phosphorus compounds.
• Elevated enzymes can be seen in cases of acute myocardial infarction (AMI).