MLAB 2401: Clinical Chemistry
Keri Brophy-Martinez
Plasma Proteins
Plasma Proteins

Two groups
◦ Albumin
◦ Globulins
Prealbumin
◦ Synthesized mainly in the liver
◦ Migrates ahead of albumin on electrophoresis
◦ Transport protein for thyroid hormones and
retinol(Vitamin A)
Decreased Levels




Hepatic damage
Acute-phase inflammatory
responses
Tissue necrosis
Poor nutrition
Increased Levels



Steroid therapy
Alcoholism
Chronic renal failure
Prealbumin
Albumin
•
•
•
Synthesized in the liver
Protein present in the highest
concentration in the plasma
Functions
– Maintenance of colloid osmotic pressure
– Buffers pH
– Negative acute phase reactant
– Binds substances in the blood
Decreased Levels
•
Increased Levels
Malnutrition/Malabsorption

– Inadequate intake of amino acids

•
Liver disease
•
GI loss
Dehydration
Excessive albumin infusion
– Loss of fluids
•
Renal disease
– Excreted excessively
•
Dilution by excess
– IV fluids, polydipsia
Albumin
Globulins
Group consisting of α1, β, α2, and gamma
fractions
 Focus will be on globulins most often
encountered in the lab

α1- Globulins
Globulin
Function
Increased
Decreased
α1-Antitrypsin
Acute phase
reactant
Inflammatory
reactions,
pregnancy,
contraceptive use
Neonatal
Emphysema
α1-Fetoprotein
Principal
fetal protein
Spina bifida
Anencephaly
Fetal Distress
α2- Globulins
Globulin
Function
Increased
Decreased
Haptoglobin
•Acute phase reactant
•Binds hemoglobin
•Inflammatory diseases
•Rheumatic disease
•Hemolytic anemia
•Liver disease
Ceruloplasmin
•Acute phase reactant
•Redox activity
•90% copper found
here
•Inflammation
•Severe infection
•Tissue damage
•Pregnancy
•Others
•Wilson’s disease
•Malnutrition
•Malabsorption
•Severe liver disease
•Others
α2-Macroglobulin
•Inhibits proteases
•Nephrosis
•Diabetes
•Liver disease
β- Globulins
Globulin
Function
Increased
Decreased
Transferrin
•Transports iron
•Prevents iron loss
•Negative acute phase
reactant
•IDA
•Liver disease
•Nephrotic syndrome
•Malnutrition
Hemopexin
•Acute phase reactant
•Binds free heme
•Inflammation
•Diabetes melllitus
•Melanoma
•Hemolytic anemia
Lipoprotein
•Transports lipids, mainly
LDL
•Atherosclerosis
•Heart disease
•Diabetes mellitus
•Hypothyroidism
ß- Globulins (con’t)
Globulin
Function
Increased
Decreased
Fibrinogen
•Precursor of fibrin clot
•Acute phase of
inflammatory processes
•Pregnancy
•Oral contraceptives
Excessive coagulation
Complement
•Immune response
•Inflammation
•Malnutrition
•Hemolytic anemia
CRP
•Acute phase reactant
•Tissue necrosis
•Cardiac disease
γ- Globulins: Immunoglobulins
Globulin
Function
Increased
Decreased
IgG
Antibodies
•Liver disease
•Infections
•Parasitic disease
•Others
•Immunodeficiency
•Others
IgA
Antibodies in
secretions
•Liver disease
•Infections
•Autoimmune disease
•Immunodeficiency
•Decreased protein
synthesis
IgM
Antibodies: early
response
•Toxoplasmosis
•Others
•Hereditary
immunodeficiency
IgD
Antibodies
•Infections
•Liver disease
IgE
Antibodies: allergies
•Not diagnostic
Other Noteworthy Proteins
Myoglobin
 Troponin

◦ Heart marker for MI

BNP
◦ Distinguishes between MI and CHF

Fibronectin
◦ Glycoprotein used to predict the short term
risk of premature delivery
Do you feel like this?
If the answer is “Yes” take a break!
Protein Abnormalities
Total protein measures ALL of the
proteins in plasma
 Measurements reflect

◦
◦
◦
◦
Nutritional status
Kidney disease
Liver disease
Other
Hypoproteinemia
Total protein level <6.4 g/dL
 Due to a negative nitrogen balance
 Causes
◦ Excessive loss
 renal disease, blood loss, burns
◦ Decreased intake
 Malnutrition, intestinal malabsorption
◦ Decreased synthesis
 Liver disease, inherited immunodeficiency
◦ Acceleration of catabolism of proteins
 Burns, trauma

Hyperproteinemia
Total protein level > 8.3 g/dL
 Causes

◦ Dehydration
 Excess water loss leads to the increased
concentration of proteins
 Examples: vomiting, diarrhea, diabetic acidosis,
hypoaldosteronism
◦ Excessive production of gamma globulins
 Examples: Multiple myeloma, Waldenstrom’s
macroglobulinemia
Summary of Protein Levels
Total Protein
Albumin Globulin
Disease
N, D
D
I
Hepatic damage, Burns, trauma, Infections
D
D
N
Malabsorption, Inadequate diet,
nephroticsyndrome
D
N
D
Immunodeficiency syndromes
I
I
I
Dehydration
I
N
I
Multiple myeloma, monoclonal and
polyclonal gammopathies
N= normal
I=increased
D=decreased
References
Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry:
Techniques, principles, Correlations. Baltimore: Wolters
Kluwer Lippincott Williams & Wilkins.
 Sunheimer, R., & Graves, L. (2010). Clinical Laboratory
Chemistry. Upper Saddle River: Pearson.
 http://www.stoelrivesworldofemployment.com/tags/rest
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