PLT in a blood test: rate, reasons for increase and decrease
The content of the article:
- Platelet function
- Blood platelet test and how to prepare for it
- PLT rate
- Decreased blood platelet count
- Elevated level of platelets in the blood
PLT in a blood test is an indicator of the proportion of platelets per unit of blood volume (from the English platelets - platelets). Determination of PLT in blood is used in the initial assessment of the state of the blood coagulation system, before surgery, invasive diagnostic procedures, in the diagnosis of thrombosis, suspicion of the presence of myeloproliferative diseases.
A blood test for PLT is carried out as part of a complete blood count, it is prescribed in cases of unexplained or prolonged bleeding, bleeding gums, nosebleeds, excess blood during menstruation, to assess the effectiveness of treatment of bone marrow diseases.
Platelets are the smallest blood cells, the diameter of each does not exceed 2-3 microns, have a round or oval flat shape, because of which they are called platelets. The material for the formation of platelets is the cytoplasm of megakaryocytes - giant cells of the red bone marrow.
Platelets have a protective function
Platelets are non-nuclear, colorless formations surrounded by a membrane, containing a large number of granules. On the surface of the plates are glycoprotein formations that function as receptors. The lifespan of cells is about seven days; their inactivation and utilization occurs in the liver and spleen.
Platelet function
The main function of platelets is blood clotting; it is they that provide a protective reaction of the body, which prevents massive blood loss in case of vascular damage.
From the bone marrow, platelets enter the bloodstream, some of them remain in the spleen. In an intact vessel, the plates do not interact with each other; their physiological activation begins only after the vessel is injured. Due to the presence of collagen receptors on their surface, a chain of reactions develops in response to damage to the vessel. Physiological activation begins with adhesion, a phenomenon that allows the plates to adhere to other surfaces and be held in places with high blood flow rates. When in contact with a foreign surface, which differs in its properties from the endothelium, the platelet swells, spreads and acquires a stellate shape with filamentous processes that significantly exceed its diameter. Simultaneously with adhesion, the process of aggregation occurs - swelling and adhesion of platelets to each other,the formation of a platelet plug in the damaged area of the vessel.
Platelets have phagocytic activity, contain IgG, and take part in protecting the body from bacteria. The granules and the platelet membrane contain platelet factors, which are the source of lysozyme and β-lysines, which can destroy the membranes of foreign agents.
Also, platelets perform an angiotrophic function, which is to feed the endothelium of blood vessels.
Blood platelet test and how to prepare for it
For analysis for PLT, blood is taken from a finger, less often from a vein. Blood must be taken in the morning, on an empty stomach, at least eight hours after the last meal. Before taking blood, you can only drink water.
It should be borne in mind that the number of platelets increases with stress, painful irritation, smoking, physical exertion. This means that on the eve of donating blood, you need to quit smoking, drinking alcohol, physical activity, stop taking certain medications - this will avoid distorting the results.
PLT rate
The level of platelets in the blood is determined in the number of plates per 1 μL of the blood sample. For adult men, the PLT rate is 200,000–400,000 U / μl, for women - 180,000–320000 U / μl. During menstruation, the level of platelets in the blood decreases slightly. Changes in PLT levels during pregnancy are also due to physiological reasons.
In children, the rate of platelet count in the blood depends on age. To decipher the results of a blood test for PLT, you can consult the table in which several age groups are distinguished.
PLT rate in children
| Age | PLT content in blood, U / μl |
| Newborn | 100,000-420,000 |
| 2 weeks to 12 months | 150,000-350,000 |
| 1 to 5 years | 180,000-380,000 |
| 5-7 years old | 180,000-320,000 |
| Over 7 years old | 320,000-450,000 |
The norm values may differ depending on the method of determination, conditions (equipment, reagents) of the laboratory, units of measurement. An increase or decrease in the level of platelets in the blood is always interpreted in conjunction with other indicators of the general analysis.
Decreased blood platelet count
A decrease in the concentration of platelets in the blood (thrombocytopenia) can result from a decrease in their production in the bone marrow, excessive destruction or improper redistribution in the bloodstream, mutations, and a deficiency of vitamin B12 or folic acid. Most of all thrombocytopenias are immune forms. If the level of PLT in the blood is low, bleeding develops.
The reasons for the low PLT content can be anemia, autoimmune thrombocytopenic purpura, viral liver pathologies, increased spleen activity, lupus erythematosus, diseases associated with thyroid dysfunction, disseminated intravascular coagulation syndrome, bone marrow lesions, leukemia, taking corticosteroids, antibiotics, cytostatics, diuretics.
A sign of a decrease in the PLT level is gingival, nose and other bleeding.
Thrombocytopenia symptoms:
- intense bleeding after tooth extraction or other invasive procedures;
- prolonged and heavy menstrual bleeding;
- spontaneous nasal, gingival, pulmonary, renal, gastrointestinal, uterine bleeding, hemorrhage into the joint cavity;
- frequent appearance of hematomas, small-point rash on the body and limbs;
- enlargement of the spleen;
- joint pain.
Elevated level of platelets in the blood
An increase in the number of platelets in the blood (thrombocytosis) can be caused by microcirculatory disorders, a defect in stem cells, intravascular coagulation of blood cells, nonspecific activation of the hormone thrombopoietin, which regulates the flow of platelets into the blood, impaired platelet aggregation ability. When the number of platelets in the blood exceeds the norm, there is a risk of blood clots.
Elevated PLT may indicate the development of acute or chronic infections, inflammatory bowel diseases, osteomyelitis, lupus erythematosus, rheumatoid arthritis, collagenosis, sarcoidosis, tuberculosis, renal failure, liver cirrhosis, malignant neoplasms of the stomach, lungs, ovaries, malignant blood diseases, sepsis. The cause of thrombocytosis can be conditions after surgery, trauma, fractures of large bones, profuse blood loss, removal of the spleen, as well as iron deficiency in the body, taking glucocorticosteroids, chemotherapy.
Symptoms of an elevated blood platelet count:
- thrombosis of veins, less often of arteries;
- nasal, gingival, uterine, renal, intestinal bleeding;
- hemorrhages of subcutaneous localization;
- blood in the stool;
- anemia;
- joint pain;
- numbness and tingling in the limbs;
- itchy skin;
- migraine;
- instability of blood pressure, tachycardia;
- cyanosis of the skin;
- susceptibility to infectious diseases;
- visual impairment;
- enlargement of the liver and / or spleen.
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Anna Kozlova Medical journalist About the author
Education: Rostov State Medical University, specialty "General Medicine".
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