Blood test methods

Despite the undeniable importance of data obtained using special methods, generally accepted methods of clinical examination of the patient can also provide valuable information.

Complaints

Most patients have non-specific complaints and are often limited to general weakness, headaches, shortness of breath, abdominal pain, and bleeding. Often there is an increase in body temperature (from subfebrile to fever, accompanied by chills and sweats), loss of appetite, and weight loss (also common symptoms of many diseases of various organs and systems). Severe anemia is a characteristic manifestation of increased blood loss in blood diseases, but is often a consequence of repeated bleeding in gastric ulcers, hemorrhoids, and gynecological pathology.

Weight loss, often combined with loss of appetite, is especially pronounced in malignant blood diseases (leukemia, lymphoma). Sometimes a peculiar change (distortion) of taste and smell is noted - for example, a passion for the use of chalk, coal, the smell of gasoline, which is observed in patients with iron deficiency anemia (chlorosis).

Fever is a frequent manifestation of both hematological diseases themselves and their infectious complications. Subfebrile condition of a prolonged nature is observed in various anemias, high fever is a typical sign of acute leukemia and lymphogranulomatosis. Usually, fever of this origin is accompanied by profuse sweating, chills, weight loss, pronounced general weakness and malaise.

Complaints of bleeding, manifested by hemorrhagic rashes on the skin, nosebleeds, gastrointestinal and uterine bleeding, are quite typical in blood diseases.

A significant enlargement of the liver and spleen can manifest itself as pain, stretching of the capsule, especially if the enlargement of the organ occurs quickly.

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Medical history

When studying the anamnesis of the disease, it is very important to find out the possible causes of the disease. In this regard, it should be borne in mind that often changes in the blood are secondary in nature and are one of the signs of the disease of other organs and systems. Particular attention is paid to the possible hematological effects of previously taken medications, including on the patient's own initiative - with widespread self-medication with analgesics, laxatives, tranquilizers.

When clarifying the family history, it is important to find out whether the patient's relatives have jaundice, anemia, cholelithiasis (hereditary hemolysis); in case of bleeding, you should ask about similar manifestations in close relatives; it is important to establish the fact of death of brothers and sisters in early childhood. The prevalence of the disease among male relatives in different generations is especially characteristic of hemophilia.

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Physical methods of blood testing

A physical examination is carried out in full, including elements of a general examination and study of individual organs and systems.

The skin and mucous membranes may be altered due to direct changes in the properties of the blood flowing through the capillaries, as well as the deposition of pigments in the skin.

Pallor may be due to anemia, and redness of the skin - to erythrocytosis, although transient pallor may be associated with exposure to cold, and erythematous complexion - with frequent alcohol consumption, exposure to both low and high temperatures, etc. A more reliable sign of anemia and erythrocytosis is the pale color of the mucous membranes and nail beds. Yellowish coloration of the skin and mucous membranes often occurs with hemolysis.

Petechiae and ecchymoses are bleeding on the skin due to vasculitis or blood clotting disorders.

Traces of scratching associated with itching are characteristic of lymphogranulomatosis.

Changes in the shape of nails, their thickening, and the appearance of striations are signs of iron deficiency.

The appearance of ulcers on the oral mucosa is characteristic of agranulocytosis. In leukemia, gum infiltration, hyperemia, and bleeding are possible. A tongue with smoothed papillae is found in iron deficiency and pernicious anemia.

Lymph nodes are often involved in the pathological process. It is advisable to palpate the lymph nodes sequentially, starting with the occipital, then palpate the submandibular, submental, cervical, supraclavicular, axillary, elbow, and inguinal. Palpation should be done with soft circular movements of the fingertips. Pay attention to their size, consistency, and soreness. Enlargement of the cervical and supraclavicular nodes may be regional in nature (more often with tonsillitis and the presence of carious teeth). Nodes located in the chest area at the roots of the lungs can be detected radiologically, and in the abdominal cavity - with the help of computed tomography or ultrasound. Enlargement of the lymph nodes is characteristic of leukemia, primarily chronic lymphocytic leukemia, as well as lymphogranulomatosis.

Bone changes are quite common. Bone pain can be both generalized (in leukemia) and localized (in myeloma and bone metastases). It is advisable to palpate the bone surface to identify possible foci of disease.

Liver enlargement is detected using both physical (palpation, percussion) and instrumental methods (ultrasound and computed tomography). Hepatomegaly is detected in leukemia and hemolysis.

Examination of the spleen is very important. The most reliable method for detecting an enlarged spleen is palpation. Percussion of this organ is less conclusive (see the chapter on liver diseases). Normally, the spleen cannot be palpated. Attention is paid to the size of the spleen, its consistency, and soreness. With severe splenomegaly, the lower pole may protrude far from under the left costal arch. Sometimes it is advisable to palpate the spleen in a position both on the right side and on the back.

In the left upper quadrant of the abdomen, a formation associated with other organs (kidney, left lobe of the liver, pancreas, colon) can be palpated. Sometimes it is difficult to distinguish them from the spleen, and in these cases, ultrasound and other instrumental methods should be used to identify the palpable formation.

In blood diseases, the nervous system is often affected, especially with vitamin B12 deficiency, leukemia and hemorrhagic diathesis.

Additional research methods

In diseases of the hematopoietic system, the following special research methods are used: general clinical blood analysis, examination of bone marrow punctures, lymph nodes, spleen. Histological, cytochemical, cytogenetic, radiological, ultrasound, radioisotope research methods are used.

A general blood test determines the hemoglobin content, the number of erythrocytes, other indicators, often leukocytes, platelets, calculates the leukocyte formula, and determines the ESR. This analysis can be supplemented by determining the number of reticulocytes.

Usually, capillary blood is examined, obtained by pricking the flesh of the fourth finger of the left hand, or blood from the ulnar vein. Scarifying needles are used, which are then washed and sterilized by boiling or placing in a drying cabinet at 180 °C for 2 hours.

The skin at the injection site is wiped with a cotton swab soaked in alcohol, then ether. It is better to inject at a depth of 2-3 mm.

It is advisable to take blood in the morning on an empty stomach. However, if necessary, the blood test can be done at any time of the day.

Methods for determining hemoglobin levels, counting red blood cells, white blood cells, platelets, and the white blood cell count are discussed in detail in special publications, including a description of modern methods for counting these particles using special electronic counters (Celloscope, Coulter).

Despite the enormous importance of peripheral blood testing, it must be emphasized that the results of a complete blood count should only be assessed in conjunction with all other clinical data, especially during dynamic monitoring of the patient.

An increase in the number of red blood cells in the blood (erythrocytosis) can be short-term (for example, during heavy physical exertion, in mountainous areas) or be of a longer-term nature (chronic pulmonary insufficiency, congenital heart defects, erythremia, kidney tumors). Usually, in both cases, an increase in hemoglobin content is observed.

The number of erythrocytes and the level of hemoglobin decrease in anemia (especially quickly in severe hemolysis, bleeding), as well as in acute and chronic infections (flu, sepsis, etc.), chronic renal failure and, of course, under the influence of various drugs (chloramphenicol, cytostatics, etc.). In a number of these situations, a change in the number of reticulocytes is noted; their decrease in aplastic, iron deficiency and megaloblastic anemia, leukemia; their increase in hemolysis, acute posthemorrhagic anemia; of clinical interest is the appearance of significant reticulocytosis during dynamic observation several days after the administration of vitamin B ₁₂ in the case of pernicious anemia (reticulocyte crisis on the 7-10th day of treatment).

A sign of insufficient maturation of erythrocytes is the appearance of so-called basophilic granularity in erythrocytes, which is especially characteristic of anemia associated with lead intoxication. In case of erythropoiesis disorders, red blood cell nuclei - normoblasts - may be found in the peripheral blood.

Of great clinical significance are such frequently occurring morphological changes in red blood cells as the presence of red blood cells of different sizes (anisocytosis), which may be combined with changes in their shape (poikilocytosis), the predominance of small red blood cells (microcytosis) or large (macrocytosis) sizes (less than 6 μm or more than 8 μm, respectively, with a normal average red blood cell diameter of 7.2 μm). Determining the red blood cell diameter allows for graphic recording of the red blood cell distribution by size in the form of the so-called Price-Jones curve, which particularly clearly reveals micro- and macrocytosis. Usually, these conditions are accompanied by a change in the hemoglobin content of red blood cells, determined by the color index (or, which is becoming more common, by the weight content of hemoglobin in red blood cells - the ratio of the hemoglobin content in 1 liter of blood to the number of red blood cells in the same volume, with one red blood cell normally containing 27-33 ng of hemoglobin). Microcytosis reveals a decrease, while macrocytosis reveals an increase in the hemoglobin content in one erythrocyte. Thus, the most common iron deficiency anemia is usually accompanied by microcytosis and a decreased hemoglobin content in one erythrocyte.

It is important to determine the ratio between the volume of red blood cells and the volume of plasma - this indicator is called the hematocrit number, or hematocrit. Special centrifuges have been created in which a hematocrit tube is placed. As a result of the study, it is determined what part of the blood is made up of red blood cells. Using the electronic-automatic method with the help of the Coulter and Celloskop devices, the hematocrit is measured simultaneously with the calculation of the average volume of the red blood cell and the total volume of red blood cells, after which, knowing the volume of blood, the hematocrit is determined. When the blood thickens (with vomiting, diarrhea, other situations with a large loss of fluid), the volume of red blood cells increases due to a decrease in the volume of plasma.

The results of the study of leukocytes are of great clinical significance - the total number of leukocytes and the percentage of their individual forms.

The change in the total number of leukocytes, either upward (leukocytosis) or downward (leukopenia, leukopenia), can be an important diagnostic sign in itself, the value of which increases with repeated blood tests (an increase in these changes certainly indicates progression of the process). But the combined study of the leukogram - the leukocyte formula (the percentage of individual forms of leukocytes in the peripheral blood) is especially important, since it is the leukocytes that react to external and internal changes earlier and faster than other blood elements. Leukocytosis is characteristic of acute bacterial infections. In this case, a shift in the formula to the left - an increase in the content of young forms of neutrophils (band neutrophils), the appearance of young neutrophils indicates an early stage of the process. High neutrophilic leukocytosis is characteristic of localized inflammatory processes (lung abscesses, etc.), including those with the development of tissue necrosis (burns, myocardial infarction), malignant tumors during the period of decay, as well as rheumatism, endogenous and exogenous intoxications (uremia, diabetic acidosis, mushroom poisoning, etc.), drug effects (corticosteroids). Myeloproliferative diseases (chronic myeloleukemia, erythremia) should be especially mentioned, in which, in addition to leukocytosis, there are also changes in the leukocyte formula. Leukemoid reactions resemble blood changes in leukemia (significant leukocytosis with "rejuvenation" of the formula), but are reactive in nature, being associated, for example, with tumors.

Eosinophilia occurs in allergies (bronchial asthma, drug intolerance), parasitic infestations (trichinellosis, ascariasis, etc.), skin diseases (psoriasis, pemphigus), tumors, and other diseases (periarteritis nodosa); basophilia occurs in myeloleukemia, erythremia; in a rare disease, mastocytosis, there is infiltration of various organs by these cells; monocytosis is observed in infective endocarditis, tuberculosis, and systemic diseases (systemic lupus, rheumatoid arthritis).

Lymphocytosis is characteristic of viral and chronic bacterial infections, lymphatic leukemia, and lymphomas.

Leukopenia is a characteristic sign of some infections (primarily viral), exposure to ionizing radiation, many drugs (primarily immunosuppressants), bone marrow aplasia, autoimmune systemic diseases (systemic lupus erythematosus, etc.), redistribution and sequestration of leukocytes in organs (anaphylactic shock, Felty's syndrome, splenomegaly of various origins). Agranulocytosis, which can be myelotoxic (radiation, cytostatic agents) and immune (systemic lupus erythematosus, drug-induced lesions), should be especially noted.

Qualitative changes in leukocytes are of lesser clinical significance. Toxic granulation of neutrophils is observed in severe infections and toxicoses. The LE-cell phenomenon is observed in systemic lupus erythematosus and includes the appearance of "lupus cells" (LE cells) - neutrophilic leukocytes that include phagocytic homogeneous nuclear material. In addition, hematoxylin bodies (nuclear material) and "rosettes" - formations of neutrophils that surround the nuclear material in a ring - appear.

ESR depends to the greatest extent on the protein composition of blood plasma, especially on the content of fibrinogen and immunoglobulins. The degree of acceleration depends on the relationship in the content of some proteins. ESR increases especially noticeably when proteins - paraproteins - appear in plasma, which is typical, for example, for myeloma disease. Currently, paraproteins can be identified.

The ESR is also affected by the plasma pH (it decreases in acidosis, increases in alkalosis); in anemia, the ESR increases, and in erythrocytosis, it slows down.

Bone marrow examination is widely used in clinical practice. The material for its study is obtained by puncturing spongy bones, usually the sternum in the upper third of the body (sternal puncture), the ilium (trephine biopsy). The need for these studies arises in various situations: anemia, the nature of which remains unclear (despite various non-invasive studies); leukemia, pancytopenia, tumor process (to exclude or confirm metastases).

Cytochemical examination of leukocytes is used to identify, in particular, tumor lesions of the blood. Of particular importance are the differences in granules in some types of granulocytes at different stages of their differentiation, which is especially effectively detected using monoclonal antibodies to membrane proteins, which make it easier to distinguish subpopulations of lymphocytes. The blood of patients is examined for the content of peroxidase, alkaline phosphatase, esterases and a number of other enzymes in leukocytes.

Cytogenetic research is carried out to identify anomalies in the number and morphology of cell chromosomes. Thus, the appearance of the Philadelphia chromosome in chronic myelogenous leukemia is well known.

The study of hemorrhagic syndrome is also important, since blood clotting disorders with the development of bleeding may be associated with a deficiency in the number of platelets, changes in coagulability due to a violation of the content of humoral clotting factors in the blood, and pathological “fragility” of blood vessels.

Clinical manifestations of hemorrhagic syndrome sometimes allow us to assume its causes. Thus, petechiae (small hemorrhages on the skin) are often associated with a lack of platelets or damage to the vascular wall, large subcutaneous hemorrhages (ecchymoses) allow us to assume a blood clotting disorder due to liver disease, and hemarthroses indicate hemophilia.

The combination of small petechiae and ecchymoses is possible due to the presence of vascular damage, most likely of an immune complex nature.

Telangiectasias on the lips and mucous membranes can explain hemoptysis, intestinal bleeding, hematuria.

In the blood clotting process, platelets circulating in the blood, which are formed from bone marrow megakaryocytes, play an important role.

The platelet count is made in a blood smear per 1000 erythrocytes. Knowing the number of erythrocytes in 1 µl of blood, the platelet count is also determined. Electronic automatic counters such as "Celloscope" and "Culter" are also used.

A decrease in the number of platelets (thrombocytopenia) and the resulting bleeding develop significantly more often than thrombocytosis and occur in Werlhof's disease, autoimmune, medicinal, and radiation exposure.

The state of platelet-microcirculatory hemostasis is reflected by such indicators as the duration of bleeding according to Duke I and the retraction of the blood clot.

Capillary resistance is assessed using the "pinch symptom": a hemorrhage appears at the site of the pinch. The "tourniquet symptom" has a similar meaning: a tonometer cuff is applied to the shoulder for 3 minutes at a pressure of 50 mm Hg; with a positive symptom, a significant number of petechiae appear.

Using special devices, it is possible to study such properties of platelets as aggregation and adhesion.

Coagulation hemostasis is characterized by an integral coagulation indicator - the clotting time of whole blood. Determination of thrombin and prothrombin time, prothrombin index, and a number of other indicators are also of clinical importance.

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