Table of contents
What is total protein?
When the cells of our circulating blood are separated by centrifugation, 55% consists of plasma and 45% blood cells. Plasma is the liquid part outside the cells. Plasma is made up of 90% water. 10% of the plasma consists of dissolved substances. The vast majority of these substances are proteins. What remains are electrolytes, waste and other substances. The blood total protein test is the amount of total protein in the plasma.
Most of the dissolved substances in blood plasma are proteins. The mean total protein level of blood plasma or serum in a healthy adult human is 7 g/dL (5.7-8.0 g/dL). It has been determined that there are about 300 proteins in the blood plasma. While some of them are actively present in the blood, some of them occur due to developing conditions. Some may be extravasated when there is cell damage while circulating in the plasma. While some are dissolved in plasma, their plasma levels are increased if needed.
Plasma total protein:
- 5-5.0 g/dL of serum albumin,
- globulins as much as 2.5-3.2 g/dL
- The rest are other proteins.
The plasma part of the blood contains biologically active compounds (hormones, enzymes, nutrients and waste products). The plasma content is kept within very strict limits. Significant changes in these limits are indicative of dysfunction. It reflects the functions of organs such as the heart, lungs, liver and kidneys. In healthy individuals, the blood total protein level shows very rare deviations. Therefore, even a change in the blood above 0.8g/dL is considered abnormal.
What are the functions of plasma proteins?
- They contribute to the balance of blood pressure.
- They carry many substances in the plasma to the relevant places by holding them from where they are in case of need.
- They keep water in the vascular bed by providing plasma tone.
- They affect blood viscosity
- They contribute to maintaining the acid-base balance of the blood.
- They contribute to the maintenance of blood suspension stability.
- They meet the protein needs of the tissues
- They contribute to the protection of the organism against infections and harmful substances.
Types of proteins in the blood
Plasma proteins are generally classified into three classes:
- Albumin- constitutes 60% of plasma proteins, is responsible for the formation of osmotic pressure.
- Globulins – make up 38% of plasma proteins. It consists of α,β,γ, sub-fractions.
- α and β globulins transport fats and fat-soluble vitamins
- It carries γ globulin antibodies.
- Fibrinogen- accounts for 2% of plasma proteins and is a coagulation factor.
Plasma proteins are generally produced in the liver. Each plasma protein has a specific half-life. For example, Albumin has a half-life of 20 days, while haptoglobulin has a half-life of 5 days.
The plasma level of some plasma proteins is increased or decreased in acute reactions or in some types of tissue injury.
Plasma proteins increased in various reactions or injuries (positive acute phase reactants):
- CRP
- Alpha1 antitrypsin
- Haptoglobulin
- Alpha1 acidglycoprotein
- Fibrinogen
- Ceruloplasmin
- C3, C4
- IgG, IgM, IgA
- Beta2-microglobulin
Decreased plasma proteins in various reactions or damage (negative acute phase reactants):
- Transferrin
- Albumin
- Prealbumin
- Retinol binding protein
Increased protein in the blood
Conditions in which the level of total protein in the blood is increased (Hyperproteinemia):
- Conditions in which plasma water content is reduced (relative hyperproteinemia)
- Dehydration with diarrhea and vomiting
- Water loss through the skin in hot environments and febrile diseases
- Kidney failure
- Salt wasting nephritis
- Diabetes mellitus
- Fluid loss due to the use of diuretics
- Water loss through the kidneys in case of polyuria
- Restriction of water intake
- Conditions of paraproteinemia (Finding of proteins not normally found in the blood)
- Multiple myeloma
- Lymphoreticular system malignancies
- Autoimmune diseases such as rheumatoid arthritis
- Severe chronic infections
- Cirrhosis of the liver
- Some chronic diseases (They cause increased gamma globulin)
- Severe chronic polyarthritis
- Endocarditis
- Tuberculosis
- Malaria
- Kala-azar
- Leprosy
- Various tropical diseases such as filariasis
- Cirrhosis of the liver
- Sarcoidosis
- Rheumatoid arthritis (RA)
- Systemic lupus erythematosus (SLE)
Decreased protein in the blood
Conditions in which the level of total protein in the blood decreases (Hypoproteinemia):
- Conditions with increased plasma water content (relative hypoproteinemia)
- Salt retention in the body
- Excessive fluid intake (water intoxication)
- Heart failure condition
- Removal of blood from the fluidized arm
- Excessive protein loss
- Nephrotic syndrome
- Chronic glomerulonephritis
- Burns
- Irritating wounds and skin lesions
- Psoriasis
- Protein-losing enteropathy
- Stomach polyp
- Ulcerative gastritis
- Surgical and traumatic shocks
- Excess fluid draining from body cavities
- Hyperthyroidism
- Diabetes mellitus
- Pregnancy toxemias
- Conditions where there is a decrease in protein synthesis
- Kwashiorkor disease
- Severe malabsorption states
- Protein-poor diet
- Severe liver diseases
- Protein metabolism disorder
If the result of the total protein test is abnormal, further testing, such as protein electrophoresis, may be needed to determine which proteins are too high or too low.