Generality
High platelets circulating in the blood are an index of thrombocytosis (also known as platelet or thrombocythaemia ).
The finding of this alteration can signal the presence of a very large variety of physiological or pathological conditions. The most frequent causes include hematological diseases, inflammation, intense physical exertion, iron deficiency, infections and tumors.
High blood platelets are found during a blood count (or blood count), performed for an occasional check-up or for the appearance of symptoms associated with a thrombotic or hemorrhagic event.
In addition to establishing a state of thrombocytosis, this blood test can help diagnose a number of conditions associated with a high number of platelets, such as, for example, bone marrow disorders or haemostatic disorders.
High platelets can increase the risk of thrombotic complications, especially when this alteration is chronic.
What are
Physiologically, 150, 000 to 450, 000 platelets are present in one microliter of blood circulating in the body. In some conditions, however, this value can increase beyond the maximum reference threshold: we speak, then, of high platelets .
To remember! High platelets define a condition called platelet, thrombocytosis or thrombocythemia.
In most cases, the increase in blood platelet levels depends on the presence in the body of a stimulus (transient or chronic) that causes the bone marrow to increase the production of these elements.
Platelets: short introduction
- What they are - Platelets (or thrombocytes) are small corpuscular elements of the blood, with no nucleus. They are produced by the bone marrow, starting from precursors called megakaryocytes, which derive from hematopoietic stem cells.
- What is their function - Once released into the bloodstream, platelets play a fundamental role in the coagulation process and in the regulation of hemostasis (ie in the blockage of bleeding, which follows any lesion). When damage occurs to blood vessels or tissues and blood loss begins, they adhere to each other and clump together to form a sort of cork, which remains in the area, until the damage is resolved. At the same time, platelets release chemicals that stimulate the intervention of other coagulation factors.
- How much they remain in circulation - The average life of platelets is 8-10 days; the bone marrow must continuously produce new elements to replace those that are degraded, consumed and / or lost during bleeding. An excessive lowering of the level of thrombocytes increases the risk of incurring bleeding, while an increase in these cells increases, on the contrary, the predisposition to thrombosis correlated to the formation of platelet aggregates.
Because they measure themselves
High blood platelets are found during a blood count (or blood count ), performed as part of a general check on the patient's state of health or after the appearance of symptoms associated with a thrombotic or hemorrhagic event.
The presence of a platelet count higher than the physiological values must be confirmed with subsequent blood counts, repeated several weeks or months later, to exclude a transient form of thrombocytosis.
If the platelets are persistently high, further tests will be suggested by the hematologist to investigate the situation and confirm the suspected diagnosis.
Platelet parameters
The total number of platelets per blood volume ( PLT ) is a parameter determined for a general health check. In an adult, in good health, this value is between 150, 000 and 450, 000 units per microliter of blood. High blood concentrations of platelets are an index of thrombocytosis (or platelets) .
At the same time, other platelet parameters can be measured, such as:
- Medium volume ( MPV, acronym for "Mean platelet volume"): indicates how large the platelets are in the patient's blood. This calculation is performed by an automated instrument and, if related to the platelet count (PLT), it can give an idea of the efficiency of the blood coagulation mechanisms;
- Distribution amplitude ( PDW, acronym of "Platelet Distribution Width"): expresses the degree of variability of platelet size.
- Platelet count (PCT) : commonly known as platelet count, it is a parameter analogous to the hematocrit. This value, expressed as a percentage, indicates the ratio between the total volume of platelets and the total volume of blood. The reference range is between 0.20 and 0.36%.
When is the exam prescribed?
The analysis of platelet parameters is indicated by the doctor when the patient manifests a series of symptoms attributable to the presence of platelets high in the blood, such as thrombotic tendencies (headache, dizziness, transient ischemic attacks, etc.) or, conversely, hemorrhagic (predisposition to the formation of ecchymoses, epistaxis or bleeding of the gastro-intestinal tract).
In most cases, however, high platelets are found randomly or with a blood test performed for other reasons.
The blood count can also be used to monitor patients with known platelet disorders or those being treated for such alterations, in order to verify their effectiveness.
Associated examinations
The examination of platelet parameters can be carried out together with one or more functional tests and / or other tests for the evaluation of coagulation, such as PT (Prothrombin time) and PTT (Partial Thromboplastin Time). Sometimes, while monitoring a known disease, a blood smear may be performed to examine the platelets with an optical microscope. This should be supportive in determining, for example, if the thrombocytes aggregated during the test.
To identify the possible causes of high platelets, other investigations may be necessary, such as a bone marrow biopsy or radiological examinations.
Normal values
In physiological conditions, the amount of platelets in the blood is maintained in a state of equilibrium by regeneration and elimination. The platelet count is normally between 150, 000 and 450, 000 units per µl of blood.
Note : the reference interval of the exam can change according to age, sex and instrumentation used in the analysis laboratory. For this reason, it is preferable to consult the ranges listed directly on the report. It should also be remembered that the results of the analyzes must be assessed as a whole by the general practitioner who knows the patient's medical history.
Physiological changes in platelets
High platelets can also be found in certain physiopathological conditions, such as:
- Intense and prolonged physical exercise;
- Ovulation;
- Pregnancy and puerperium;
- Post-operative or post-partum stress;
- Strong fright;
- Taking adrenergic drugs.
High platelets may also depend on a constitutional predisposition or stay at high altitudes.
Platelets High - Causes
The conditions that can be associated with high platelets are heterogeneous and numerous. On the physiopathological level, the causes of thrombocytosis can be grouped into two categories:
- Primaries;
- Secondary.
Primary (or essential) thrombocytosis
Excessive production of platelets may depend on a bone marrow malfunction caused by clonal alterations of the hematopoietic stem cell or dysfunctions of the hormonal stimulating factor platelet ail, called thrombopoietin (TPO).
This condition is found mainly in myeloproliferative syndromes, such as:
- Essential thrombocythemia;
- Polycythemia vera;
- Chronic myeloid leukemia;
- Primitive idiopathic myelofibrosis.
Secondary (or reactive) thrombocytosis
In most cases, high platelets have a reactive meaning, ie they are caused by underlying pathological conditions, which determine a stimulus to the synthesis of thrombocytes in bone marrow (medullary megakaryocytopoiesis).
The increase in the number of circulating platelets compared to the normal rate may depend on:
- Acute and chronic inflammatory processes (such as collagen diseases, vasculitis, Crohn's disease, ulcerative colitis, rheumatoid arthritis, allergopathies, sarcoidosis, infectious diseases, etc.)
- Some tumors (such as lymphomas, mesotheliomas and carcinomas of the lung, stomach, breast and ovary);
- Acute bleeding or hemolysis;
- Premature destruction of red blood cells (hemolysis);
- Asplenia, hyposplenia and splenectomy (functional insufficiency of the spleen or its surgical removal);
- Chronic iron deficiency;
- Trauma;
- Some drug therapies (eg oral contraceptives, epinephrine injection, vincristine, high dose erythropoietin, cyto-reductive chemotherapy, etc.);
- Asphyxia or hypoxic conditions (lack of oxygen);
- Tissue necrosis (secondary to bone fractures, burns or organ infarcts).
High platelets can be seen during certain blood diseases, such as:
- Lymphomas;
- Hemolytic anemias;
- Iron deficiency anemia (or iron deficiency).
How to measure them
For the evaluation of high platelets, it is sufficient to undergo a complete blood count (blood count). A sample of blood is then taken from a vein in the arm, in the morning and on an empty stomach, at the elbow.
Platelet parameters are calculated using an automated haemocytometric analysis tool. In some pathologies, high platelets can clump together and appear falsely low in number and / or high size, so it is also necessary to perform a blood smear for direct observation of cells under an optical microscope.
Preparation
To undergo blood sampling useful for the examination of platelet parameters, it is necessary to abstain from food and drink for at least 8-10 hours.
Interpretation of Results
High platelets constitute the dominant character of the clinical picture of some bone marrow diseases, such as:
- Myeloid leukemia;
- Essential thrombocythemia;
- Polycythemia vera.
Secondary thrombocytosis accompanies other pathologies, such as infectious diseases, tumors and inflammatory disorders (eg rheumatoid arthritis, enteropathies, collagenopathies, vasculitis, etc.).
Other causes of high platelets include bone fractures, acute haemorrhages due to trauma, organ infarcts and various hematological diseases (including iron deficiency anemia). Certain surgical procedures can also contribute to the onset of secondary platelet formation: this happens, for example, in the case of removal of the spleen (splenectomy), the organ responsible for the destruction of platelets.
Thrombocytosis can also be found in certain physiopathological conditions, such as hypoxia, intense exercise, post-operative stress, pregnancy and puerperium.
Risks and possible consequences
Transient secondary thrombocytosis generally does not predispose the patient to any specific consequence. When the number of platelets is very high or the platelet is chronic, instead, the risk of developing thrombotic complications increases . Because of the high circulating platelets, in fact, one can witness coagulation phenomena due to the greater aggregability of the same.
The thrombi represent the pathological exasperation of normal blood coagulation; these can cause the occlusion of a blood vessel, causing thrombosis .
In the case of primary thrombocytosis, there is an increased risk of both thrombosis and bleeding events.
In most cases, treating the cause at the origin of the high platelets, the values slowly fall within the normal ranges. In primitive thrombocytosis, on the other hand, it is necessary to use cytotoxic and / or chemotherapeutic drugs, in order to reduce platelet synthesis at the medullary level.
