Proteinemia

generality

La proteinemia is a blood chemistry parameter aimed at quantifying the total proteins present in the blood.

Normally, a healthy adult has a protein content of about 7 grams per deciliter of plasma (reference values ​​6,4 -8,3 g / dL).

What's this

• Protein is the total amount of the various types of proteins present in the liquid (plasma) part of the blood.
• The concentration of proteins in the blood is usually relatively stable, reflecting a balance between the loss of old molecules and the production of new ones.
• Albumin and globulins together account for about 95% of circulating plasma proteins, which together make up about 7% of the blood.

Proteinemia: biological significance

Blood is ideally made up of two components: a liquid fraction - which takes up just over 50% of its volume - and a cellular component (red blood cells, white blood cells and platelets).
The liquid fraction of the blood is called plasma and is made up of inorganic salts, proteins, gases, organic constituents and especially water. This blood component, like the cellular one, also has very important and essential functions for life. In particular, the biological role of plasma proteins can be summarized as follows:

• Colloidosmotic pressure regulation;
• Transport function (transferrin, ceruloplasmin, haptoglobin, hemopexin);
• Buffer function (acid-base balance);
• Defensive function (blood clotting, immunity and inflammatory response);
• Regulation of numerous activities of the organism (peptide hormones are also included among plasma proteins).

Because it is measured

Proteinmia is a test used to quantify the proteins present in the blood. Often, this parameter is measured as part of the panel of analyzes performed during routine checkups, so it is frequently used in assessing a person's general health.
The concentration of protein in the blood can provide general information about nutritional status, particularly useful when the patient has inexplicably lost weight.
Proteinemia can be prescribed together with other tests to understand the cause of an abnormal accumulation of fluid in the tissues (edema) and as an aid in the diagnosis of some liver and kidney diseases.

When is the exam prescribed?

Your doctor may order the test as part of a general check-up or to investigate the source of suspicious symptoms for liver, kidney, or bone marrow conditions, such as:

• Weight loss for no apparent reason
• Fatigue;
• Jaundice (yellowish color of the skin);
• Edema (swelling);
• Swelling around the eyes, belly or legs (signs of nephrotic syndrome).

Normal values

The reference range for proteinmia is 6,4 to 8,3 g / dL.

High Proteinemia - Cause

Protein may increase compared to the values ​​considered normal in the presence of:

• Excessive synthesis of proteins by the liver (haemoconcentration, some autoimmune diseases, etc.);
• Dehydration;
• Bone marrow disorders, such as multiple myeloma;
• Venous stasis during collection.

A high concentration of protein in the blood (hyperproteinemia) can also be observed in chronic inflammatory diseases and infections, such as viral hepatitis or HIV.

Proteinemia Bassa - Cause

A low concentration of protein in the blood (hypoproteinemia) can suggest the presence of various diseases.
In particular, the proteinemia can decrease in the following conditions:

• Reduced liver function, i.e. the liver unable to synthesize sufficient proteins for the normal functioning of the body;
• Decreased synthesis caused by insufficient dietary intake or impaired protein absorption, as occurs in malnutrition and severe liver disease. Low concentrations can also be observed in celiac disease or inflammatory bowel disease;
• Excessive catabolism or loss of protein from the kidney or intestine, as can occur in kidney disease (nephrotic syndrome);
• Increased blood volume (as in the case, for example, of congestive heart failure).

Low protein levels could also be caused by overhydration, bleeding and burns.

How it is measured

The protein test is done on a blood sample taken from a vein in the arm or collected by pricking the finger (children and adults) or the heel (infants).

Preparation

For the evaluation of proteins in the blood, it is necessary to be fasting for 8-10 hours.
Prolonged application of the tourniquet during blood sampling can lead to a false rise in protein (greater than the actual amount of circulating protein).

The drugs that can influence the result of the analysis, reducing the measured value, are estrogens and oral contraceptives.

Interpretation of Results

The results of the proteinmia are considered together with those of other analyzes and provide the physician with information on the general state of health of the patient.
If the outcome is abnormal, it is advisable to undergo further tests to identify the pathological condition that affects the concentration of protein in the blood.

High or low protein: physio-pathological significance

Plasma proteins are synthesized in the liver, except γ-globulins (produced by activated lymphocytes), hormones and some enzymes.

The catabolism of plasma proteins, on the other hand, occurs at the level of the intestinal mucosa and capillary endothelium, while normally there are no significant losses in the urine.
For what has been said, proteinemia represents an important index of liver function; in fact, faced with the finding of low concentrations of plasma proteins (hypoproteinemia), the first thought goes to the liver, which could be unable to synthesize them in adequate quantities (liver failure). However, the causes of hypoproteinemia do not always lie in the liver; the origin of this condition may in fact be:

• Hyperhydration, with increased volume (proportional reduction of all fractions)
• Decreased synthesis due to insufficient food intake. Eg: due to malabsorption, chronic liver disease, malnutrition, severe immunodeficiencies, etc.
• Protein loss from the kidney (nephrotic syndrome), from the intestine, due to haemorrhages, tumors, burns, etc.
• Excessive endogenous protein breakdown (burns, hyperthyroidism, neoplasms, overtraining).

Opposite situations are rarer, characterized by an increase in protein (iperproteinemia).
Among the possible predisposing factors we remember:

• Due to dehydration, haemoconcentration, venous stasis during sampling (proportional increase of all fractions).
• Increase of gamma-globulins (despite the decrease of albumin) in some situations of liver cirrhosis, autoimmune diseases etc.
• Presence of abnormal proteins (polyclonal or monoclonal gammopathies) etc.

In the face of altered proteinemia values, it is important to assess whether the alteration affects all or only some of the protein fractions.

NOTE: Reference values ​​for protein and other blood chemistry parameters may vary slightly from laboratory to laboratory. For this reason, it is preferable to consult the ranges reported directly on the report. It should also be remembered that the results of the analyzes must be evaluated as a whole by the general practitioner who knows the patient's medical history.