Diagnosis of iron deficiency anemia

In accordance with WHO recommendations, the following diagnostic criteria for iron deficiency anemia in children have been standardized:

• decrease in the level of SF to less than 12 μmol/l;
• increase in TIBC more than 69 μmol/l;
• transferrin iron saturation less than 17%;
• hemoglobin content below 110 g/l at the age of up to 6 years and below 120 g/l at the age of over 6 years.

Thus, WHO recommends fairly accurate criteria for diagnosing iron deficiency anemia, but diagnostic methods require taking blood from a vein and conducting fairly expensive biochemical studies, which is not always possible in Ukrainian medical institutions. There are attempts to minimize the criteria for diagnosing iron deficiency anemia.

The United States Federal Government Centers for Disease Control ( CDC) headquartered in Atlanta, Georgia, USA recommends using 2 available criteria to diagnose iron deficiency anemia: decreased hemoglobin and hematocrit (Ht) concentrations in the absence of other diseases in the patient. A presumptive diagnosis of iron deficiency anemia is made and treatment with iron preparations is prescribed for 4 weeks at a rate of 3 mg of elemental iron per 1 kg of the patient's body weight per day. The advantage of these recommendations is that the response to iron therapy is recorded according to strictly fixed criteria. By the end of the 4th week of treatment, the hemoglobin concentration should increase by 10 g/L compared to the initial level, and Ht - by 3%. Such a response confirms the diagnosis of iron deficiency anemia, and treatment is continued for several months. If no answer is received, it is recommended to stop treatment with iron preparations and review the case from the point of view of diagnostics of the process. Iron overload of the body in 4 weeks when taking iron preparations orally is unlikely.

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Laboratory diagnostics of iron deficiency anemia in children

Laboratory diagnostics of iron deficiency anemia is carried out using:

• general blood test performed using the "manual" method;
• blood test performed on an automatic blood analyzer;
• biochemical research.

When diagnosing any anemia, it is necessary to perform a general blood test with determination of the number of reticulocytes. The doctor focuses on the hypochromic and microcytic nature of the anemia. In a general blood test performed by the "manual" method, the following is revealed:

• decreased hemoglobin concentration (<110 g/l);
• normal or reduced (<3.8x10 ¹² /l) number of erythrocytes;
• decrease in color index (<0.76);
• normal (rarely slightly elevated) reticulocyte count (0.2-1.2%);
• increased erythrocyte sedimentation rate (ESR) (>12-16 mm/h);
• anisocytosis (characterized by microcytes) and poikilocytosis of erythrocytes.

The error in determining the parameters can reach 5% or more. The cost of one general blood test is about 5 US dollars.

An accurate and convenient method of diagnostics and differential diagnostics is the method of determining erythrocyte parameters on automatic blood analyzers. The study is carried out both in venous and capillary blood. The error in determining the parameters is significantly lower than with the "manual" method and is less than 1%. With the development of iron deficiency, the indicator of the severity of erythrocyte anisocytosis - RDW increases first of all (the norm is <14.5%). By determining MCV, microcytosis is recorded (the norm is 80-94 fl). In addition, the average hemoglobin content in the erythrocyte - MCH (the norm is 27-31 pg) and the average concentration of Hb in the erythrocyte - MCHC (the norm is 32-36 g / l) decrease. The cost of one analysis performed on an automatic hematology analyzer is about 3 US dollars.

Biochemical indicators confirming iron deficiency in the body are informative, but require blood sampling from a vein and are quite expensive (the cost of a single determination of SF, TIBC, SF is more than 33 US dollars). The most important criterion for iron deficiency is considered to be a decrease in the concentration of SF (<30 ng / ml). However, ferritin is an acute phase protein of inflammation, its concentration against the background of inflammation or pregnancy can be increased and "mask" the existing iron deficiency. It is necessary to keep in mind that the SF indicator is unstable, since the iron content in the body is subject to fluctuations that have a daily rhythm and depends on the diet. Transferrin saturation with iron is a calculated coefficient determined by the formula:

(SJ/OZHSS) x 100%.

Transferrin cannot be saturated with iron by more than 50%, which is due to its biochemical structure; most often, saturation is from 30 to 40%. When transferrin saturation with iron falls below 16%, effective erythropoiesis is impossible.

Examination plan for a patient with iron deficiency anemia

Tests to confirm the presence of iron deficiency anemia

1. Clinical blood test with determination of the number of reticulocytes and morphological characteristics of erythrocytes.
2. "Iron complex" of blood, including determination of serum iron level, total iron-binding capacity of serum, latent iron-binding capacity of serum, and transferrin saturation coefficient with iron.

When prescribing a study, the following factors must be taken into account to avoid errors in interpreting the results.

1. The test should be performed before starting treatment with iron preparations; if the test is performed after taking iron preparations, even for a short period of time, the obtained values do not reflect the true iron content in the serum. If the child has started taking iron preparations, the test can be performed no earlier than 10 days after their cancellation.
2. Red blood cell transfusions, often performed before the nature of the anemia has been determined, for example, when the hemoglobin level is significantly reduced, also distort the assessment of the true iron content in the serum.
3. Blood for the study should be taken in the morning hours, since there are daily fluctuations in the concentration of iron in the serum (in the morning hours, the iron level is higher). In addition, the iron content in the blood serum is affected by the phase of the menstrual cycle (immediately before and during menstruation, the level of serum iron is higher), acute hepatitis and liver cirrhosis (increase). Random variations in the parameters studied may be observed.
4. To test serum for iron content, special test tubes should be used, washed twice with distilled water, since using tap water for washing, which contains small amounts of iron, affects the results of the test. Drying cabinets should not be used to dry the test tubes, since a small amount of iron gets into the dishes from their walls when heated.

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Research to clarify the cause of iron deficiency anemia in children

1. Biochemical blood test: ALT, AST, FMFA, bilirubin, urea, creatinine, sugar, cholesterol, total protein, proteinogram.
2. General urine analysis, coprogram.
3. Analysis of feces for helminth eggs.
4. Analysis of feces for the Gregersen reaction.
5. Coagulogram with determination of dynamic properties of platelets (as indicated).
6. RNGA with intestinal group (as indicated).
7. Ultrasound of the abdominal organs, kidneys, bladder, pelvis.
8. Endoscopic examination: fibrogastroduodenoscopy, rectoscopy, fibrocolonoscopy (as indicated).
9. X-ray of the esophagus and stomach; irrigography, chest X-ray (as indicated).
10. Examination by an ENT doctor, endocrinologist, gynecologist, and other specialists (as indicated).
11. Scintigraphy to exclude Meckel's diverticulum (as indicated).

After the diagnosis of iron deficiency anemia has been established, its cause must be clarified. For this purpose, a comprehensive examination is carried out. First of all, gastrointestinal tract pathology is excluded, which may be the cause of chronic blood loss and/or impaired iron absorption. Fibrogastroduodenoscopy, colonoscopy, rectoscopy, occult blood test, and X-ray examination of the gastrointestinal tract are performed. It is necessary to persistently search for helminthic invasion by whipworm, roundworm, and hookworm. Girls and women need to be examined by a gynecologist and exclude pathology from the genital organs as the cause of iron deficiency in the body. In addition, it is necessary to clarify whether the patient suffers from hemorrhagic diathesis: thrombocytopenia, thrombocytopathy, coagulopathy, telangiectasia.

Although hematuria rarely leads to the development of iron deficiency anemia, it should be remembered that the constant loss of red blood cells in the urine cannot but lead to iron deficiency. This applies to hemoglobinuria. Iron deficiency in the body can be not only a consequence of increased blood loss, but also a result of impaired iron absorption, that is, it is necessary to exclude conditions leading to malabsorption syndrome.

Iron deficiency anemia can be caused by a condition in which blood enters a closed cavity from where iron is practically not utilized. This is possible with glomus tumors that originate from arteriovenous anastomoses. Glomus tumors are localized in the stomach, retroperitoneal space, mesentery of the small intestine, and the thickness of the anterior abdominal wall. Chronic infections, endocrine diseases, tumors, and iron transport disorders in the body can also cause iron deficiency anemia. Thus, a patient with iron deficiency anemia requires in-depth and comprehensive clinical and laboratory testing.

According to WHO recommendations, in case of difficulties in establishing the cause of iron deficiency, the term "iron deficiency anemia of unspecified origin" should be used.

Differential diagnosis of iron deficiency anemia in children

Differential diagnosis of iron deficiency anemia should be carried out with anemia in chronic diseases and anemias caused by deficiency of folic acid or vitamin B ₁₂, that is, within the group of “deficiency” anemias.

Anemia in chronic diseases is an independent nosological form with the ICD-10 code D63.8. The main causes of anemia in chronic diseases are:

• the presence of an underlying chronic disease (usually known to doctors!);
• chronic infections (tuberculosis, sepsis, osteomyelitis);
• systemic connective tissue diseases (rheumatoid arthritis, systemic lupus erythematosus);
• chronic liver diseases (hepatitis, cirrhosis);
• malignant neoplasms.

The pathogenesis of anemia development in chronic diseases is not completely clear, but the following mechanisms are known:

• disruption of iron metabolism when there is sufficient iron in the body, which makes it difficult to use iron and re-utilize it from macrophages;
• hemolysis of erythrocytes;
• suppression of erythropoiesis by inhibitors (medium molecules, lipid peroxidation products, cytokines, TNF, IL-1, replacement by tumor cells;
• Inadequate production of erythropoietin: its production increases in response to anemia, but its amount is insufficient to compensate for the anemia.

Laboratory criteria for the diagnosis of anemia in chronic diseases:

• decrease in hemoglobin concentration (mild);
• decrease in the number of red blood cells (mild);
• microcytic nature of anemia;
• normoregenerative nature of anemia;
• decrease in SJ;
• decrease in TIBC (!);
• normal or increased (!) SF content;
• increased ESR.

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