MLAB 2401: Clinical MLAB 2401: Clinical ChemistryChemistryKeri Brophy-MartinezKeri Brophy-Martinez

Plasma Proteins

Plasma ProteinsPlasma ProteinsTwo groups

◦Albumin◦Globulins

PrealbuminPrealbumin◦Synthesized mainly in the liver

◦Migrates ahead of albumin on electrophoresis

◦Transport protein for thyroid hormones and retinol(Vitamin A)

PrealbuminPrealbumin

Decreased Levels Increased Levels

Hepatic damageAcute-phase

inflammatory responses

Tissue necrosisPoor nutrition

Steroid therapyAlcoholismChronic renal failure

AlbuminAlbumin• 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

AlbuminAlbumin

Decreased Levels Increased Levels

• Malnutrition/Malabsorption– Inadequate intake of amino

acids

• Liver disease• GI loss

– Loss of fluids

• Renal disease– Excreted excessively

• Dilution by excess– IV fluids, polydipsia

DehydrationExcessive albumin

infusion

GlobulinsGlobulinsGroup consisting of α1, β, α2, and

gamma fractionsFocus will be on globulins most

often encountered in the lab

αα11- Globulins- Globulins

Globulin Function Increased Decreased

α1-Antitrypsin Acute phase reactant

Inflammatory reactions, pregnancy, contraceptive use

Neonatal Emphysema

α1-Fetoprotein Principal fetal protein

Spina bifidaAnencephalyFetal Distress

αα22- Globulins- GlobulinsGlobulin 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

ββ- Globulins- 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)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

γγ- Globulins: Immunoglobulins- 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 ProteinsOther Noteworthy ProteinsMyoglobinTroponin

◦Heart marker for MIBNP

◦Distinguishes between MI and CHFFibronectin

◦Glycoprotein used to predict the short term risk of premature delivery

Do you feel like this?Do you feel like this?

If the answer is “Yes” take a break!

Protein AbnormalitiesProtein AbnormalitiesTotal protein measures ALL of

the proteins in plasma Measurements reflect

◦Nutritional status◦Kidney disease◦Liver disease◦Other

HypoproteinemiaHypoproteinemiaTotal protein level <6.4 g/dLDue to a negative nitrogen balanceCauses

◦ 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

HyperproteinemiaHyperproteinemiaTotal protein level > 8.3 g/dLCauses

◦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 Summary of Protein LevelsLevels

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= normalI=increasedD=decreased

ReferencesReferencesBishop, 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.

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