Markers of malnutrition

Malnutrition is a condition caused by changes in food consumption or impaired utilization by the body, which leads to dysfunction at the subcellular, cellular and organ levels. Malnutrition syndrome can develop with a deficiency of any of the essential nutrients in the body (proteins, energy sources, vitamins, macro- and microelements). However, in clinical practice, protein or protein-energy malnutrition is most often observed. As a rule, with severe protein-energy malnutrition, signs of deficiency of certain vitamins, macro- and microelements are noted. Malnutrition with impaired trophic status in all its diversity (protein, energy, vitamin, etc.) is observed in 20-50% of surgical and therapeutic patients.

Nutritional assessment is now a mandatory component of medical care for hospitalized patients in leading clinics in the most developed countries of the world. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) requires that patient nutrition meet certain standards, which include:

• assessment of the patient's nutritional status;
• registration of clinical manifestations of eating disorders;
• monitoring changes in nutritional status and the patient's response to adjustments made.

The nutritional assessment process includes various methods, which can be divided into 4 groups:

• food evaluation methods;
• anthropometric (somatometric);
• clinical;
• laboratory.

These methods can be used to assess nutrition separately, but their combination is most appropriate.

Anthropometric methods of nutrition assessment are the most accessible and include measurement of:

• height (body length);
• body mass;
• abdominal, neck, shoulder, etc. circumferences;
• thickness of skin and fat folds at standard points;
• calculation of body mass index [the ratio of body weight (kg) to height (m) squared].

Anthropometric methods have great advantages: they are simple, harmless, non-invasive, can be carried out at the patient's bedside, and do not require expensive equipment. However, they have their disadvantages, which include:

• low sensitivity (do not allow detection of short-term disturbances in trophic status and do not identify specific deficiencies);
• inability to distinguish disorders caused by deficiency of any nutrient from disorders caused by imbalance between protein and energy intake;
• Some patient conditions (edema, obesity, loss of skin elasticity, turgor disturbance) do not allow for accurate measurements.

Clinical assessment of nutrition involves history taking and physical examination to detect signs and symptoms associated with nutritional status disorders. In most cases, these signs are not detectable until the malnutrition stage is advanced. Therefore, clinical assessments do not detect nutritional disorders in the early clinical or preclinical stages.

Recently, laboratory methods of nutrition assessment have increasingly become more popular in clinical practice. In primary and secondary nutritional deficiencies, tissue depots are gradually depleted, resulting in a decrease in the level of these substances or their metabolites in certain body environments, which can be detected by laboratory methods. The use of laboratory methods is also preferable from an economic point of view, since it allows detecting the initial signs of deficiency before the development of a clinical syndrome (therefore, less money will be spent on treatment), as well as identifying a deficiency of specific nutrients.

All laboratory tests for nutritional assessment can be divided into 2 categories:

• determination of the concentration of substances in the patient's blood serum;
• determination of the rate of excretion of substances in urine.

The blood serum contains newly absorbed substances that have come with food. Therefore, the concentration of a substance in the blood serum reflects the current (in time) consumption (intake) of the substance with food, i.e. it evaluates the nutritional status at one time, and not over a long period, which is very important in the treatment of emergency conditions. If the patient's renal function is not impaired, then a urine test allows us to evaluate the metabolism of minerals, vitamins and proteins. The excretion of these substances with urine also reflects the nutritional status at one time, and not the status over a long period of time.

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