Platelets are tiny blood cells that play a critical role in clotting and wound healing, and also play a key role in contributing to inflammation and immune responses.
If platelet counts drop too low, they can cause bleeding problems.
Read on to learn everything you need to know about the function of platelets, the issues that can arise, and the best way to test and analyze platelets for the purpose of scientific inquiry.
What Are Platelets?
Platelets are small fragments of membrane-bound cells found inside blood vessels. They’re formed from megakaryocytes (a type of bone marrow cell) which release large numbers of immature platelets into the bloodstream.
The platelets then circulate around the body until they stick together with other platelets or proteins called fibrinogen to form clots.
The amount of platelets circulating in your blood is known as your platelet count.
It’s usually measured in thousands per microlitre of blood. Normal counts range between 150,000 and 400,000 per microlitre.
Why Do I Need To Know About Platelets?
If you have an injury or cut, it’s important to stop bleeding quickly so that the wound doesn’t become infected.
This requires platelets to be available at high enough concentrations in order to rapidly adhere to damaged tissue and to initiate coagulation.
If you have a condition such as thrombocytopenias, where there are fewer than normal platelets in circulation, this will affect whether you bleed easily or not; in these cases, platelet transfusions may be needed to help prevent bleeding.
If you have undergone surgery, you will need to monitor how well your platelet levels recover after the operation.
Some people who undergo chemotherapy treatments may experience reduced platelet counts due to their treatment. These changes can lead to an increased risk of bleeding.
What Do Platelets Do?
Platelets are responsible for a number of functions in the body, including:
One of the most important roles carried out by platelets is clotting of the blood, which prevents the loss of blood during injuries or wounds.
When platelets come into contact with collagen, they bind together forming a meshwork structure called a platelet plug. This allows the blood to clot and stops any further bleeding.
Platelets also play an important role in the immune system. They interact with white blood cells, helping them recognize foreign invaders like bacteria and viruses.
When platelets come into contact or aggregate with each other, they release chemicals that stimulate the production of more platelets.
This process helps to maintain a steady supply of platelets in the bloodstream.
Role In Wound Healing
Platelets also contribute to the repair of tissues following injury.
For example, when skin is injured, platelets adhere to the site of damage and release growth factors that encourage new blood vessel formation and promote the migration of fibroblasts to the area.
What Are Platelet Disorders?
A disorder of platelets occurs when there are too few or too many platelets in the blood.
There are two main types of disorders:
This is caused by a decrease in the number of platelets in circulation. In some cases, this can be inherited, but it can also occur as a result of disease or medical conditions.
If a person has low platelet counts, they may develop easy bruising, nosebleeds, or hemorrhaging from cuts.
Heparin-Induced Thrombocytopenic Purpura (HIT)
This type of disorder occurs when antibodies form against specific proteins on the surface of platelets. These antibodies cause platelets to stick together and clump together, causing problems with blood flow.
People with HIT often suffer from severe headaches, fever, and sore throat. It usually resolves within a week or two of stopping heparin therapy.
How Can I Be Diagnosed With A Platelet Disorder?
There are several tests available to diagnose a platelet disorder. The first step is to check the platelet count.
If the platelet count is below 100,000 per microlitre, then a diagnosis of thrombocytopenias should be considered.
If the platelet count is above 300,000 per microlitres, then a diagnosis of idiopathic
thrombocytosis should be made.
In addition, if the platelet count drops rapidly over a short period of time, then a diagnosis of acute thrombocytopenia should be considered.
In order to confirm a diagnosis of HIT, a test known as the serotonin release assay must be performed.
This involves injecting a small amount of the patient’s blood into a tube containing a chemical that stimulates the platelets to release serotonin.
Serotonin levels in the blood are then measured using a specialized machine.
What Is Treatment For A Platelet Disorder?
The treatment options depend upon the underlying condition.
If you have a mild platelet disorder, your doctor will likely recommend no treatment at all. However, if the platelet disorder is more serious, then certain treatments may be recommended.
Treatment Options For Thrombocytopenia
Low Platelet Counts
People who have a low platelet count due to a decreased number of platelets in their bloodstream may benefit from receiving a transfusion of platelets.
Blood donors are screened for diseases such as HIV and hepatitis before donating platelets.
People who receive platelets donated by family members do not need to take any special precautions because these platelets are tested for infectious diseases prior to donation.
However, people who receive platelets donated from strangers or paid donors should be aware that they could be infected with an infectious agent.
Therefore, they should avoid sexual contact and use condoms during sex until they know whether the donor was infected with an infectious agent or had been vaccinated against one.
They should also be careful about sharing needles, toothbrushes, and razors with other people.
People who have idiopathic thrombocytosis should be monitored closely. Their platelet counts are checked regularly so that the doctors can determine how much medication to give them.
In some cases, the doctors may prescribe drugs that lower the production of white cells in the bone marrow and continue to monitor the situation.
Acute thrombocytopenic purpura (ATP) is caused by a sudden decrease in the number of platelets in the body. This problem usually affects children under 10 years old.
ATP is characterized by petechiae on the skin, bleeding gums, and nosebleeds.
The cause of this disease is unknown, and in many cases, the condition tends to resolve itself within three months without treatment. If this resolution does not occur, however, further treatment may be required.
Heparin-Induced Thrombocytopenic Purpura (HITP)
Heparin-induced thrombocytopenia is a rare but potentially life-threatening complication of heparin therapy.
It occurs when patients taking heparin develop antibodies that bind to the surface of their own platelets.
These antibodies trigger the platelets to aggregate and form clots. As a result, the person’s platelet count drops dramatically.
If left untreated, HITP can lead to severe internal organ damage and even death. Patients with HITP must therefore be treated immediately, and the first step is to stop using heparin.
Once the patient has stopped taking the drug, his platelet count should begin to increase again. If it doesn’t, the patient needs to undergo plasmapheresis.
Plasmapheresis involves removing blood plasma from the patient and replacing it with fresh blood.
This process removes the antibodies which are causing the platelet aggregation. After several sessions of plasmapheresis, the platelet count will return to normal levels.
Thrombotic Thrombocytopenic Purpura (TTP)
Thrombotic thrombocytopenic purpura (TTP), sometimes called consumptive coagulopathy, is a disorder that causes a rapid drop in platelet numbers.
TTP is characterized by the presence of microthrombi in small vessels throughout the body. Microthrombi are formed when tiny clumps of proteins called von Willebrand factor (VWF) molecules stick together.
When these VWF molecules stick together, they form long strings of a protein called “prolonged strings”. Prolonged strings of VWF then become stuck to the walls of blood vessels, where they help form more microthrombi.
In TTP, the prolonged strings of VWF are released into the bloodstream, where they interact with the platelets. Normally, platelets do not stick to each other.
But in TTP, the VWF sticks to the platelets, forming large clumps or aggregates of platelets. These clumps of platelets then block the flow of blood through the capillaries and smaller veins.
As a result, there is insufficient oxygen and nutrients delivered to the cells of the body.
The most common symptom of TTP is a sudden decrease in platelet numbers.
Other symptoms include:
- Bleeding from any part of the body
- Nausea and vomiting
- Abdominal pain
- Low red cell volume
- Loss of consciousness
- Death if untreated
Treatment for TTP includes reducing the amount of VWF in the blood, usually through Removing the VWF from the blood by means of plasmapheresis – the separation of plasma from the blood cells.
Lost fluids must also be replaced as soon as possible, and immunoglobulin and corticosteroids administered to reduce inflammation.
How Are Platelets Counted and Monitored?
A complete blood count (CBC) test measures the number of different types of white blood cells found in the blood.
The CBC test also checks for abnormalities such as anemia, low red blood cell counts, high white blood cell counts, and low platelet counts.
A differential white blood cell count examines the type of white blood cells present in the blood sample.
Differential White Blood Cell Count
As we discussed, a differential white blood cell count examines the type of white blood cells present in the blood sample.
A complete blood count is often performed first to determine if there is an underlying disease process causing changes in the number of different types of white blood cells present.
For example, a person who has leukemia may have fewer platelets than normal.
This could indicate that the person’s bone marrow isn’t producing enough platelets. The platelet count would be low because the bone marrow is unable to produce more platelets.
Other diseases may cause a decrease in the number of specific types of white blood cells, such as monocytes, eosinophils, or red blood cells.
For example, people with chronic inflammatory conditions like rheumatoid arthritis or lupus have decreased numbers of circulating monocytes.
A complete blood count will measure the total number of all types of white blood cells in your blood. It will include the following:
- Total WBCs
- Differential WBCs
- Red Blood Cells
- Mean Corpuscular Volume
- Mean Corpuscular Hemoglobin
- Mean Corpuscular Concentration
Types Of White Blood Cell
The differential counts provide information about which types of white blood cells are present in the blood.
There are four major categories:
Lymphocytes make up approximately 50% of the white blood cells in the human body. Lymphocytes are important parts of the immune system.
They fight off infections by identifying and destroying invaders, and there are two major categories of lymphocytes: B-cells and T-cells.
B-cells produce antibodies that bind to foreign substances such as viruses and bacteria. Antibodies can either kill the virus or bacteria directly or activate other white blood cells to destroy the pathogen.
T-cells are specialized white blood cells that recognize antigens on the surface of invading pathogens.
If a T-cell recognizes a particular antigen, it produces chemicals that alert nearby white blood cells to attack the invader.
Monocytes are another type of white blood cell. Monocytes are very similar to macrophages, but they don’t engulf things. Instead, they travel through the bloodstream looking for signs of infection.
When they find an invader, they release chemicals that attract other white blood cells to the area. Monocytes are involved in innate immunity, meaning that they are able to recognize pathogens without prior exposure.
Neutrophils are the most common type of white blood cell in the human body. They’re responsible for fighting bacterial infections.
Neutrophils are large and round. They move quickly through the bloodstream, gobbling up bacteria along the way.
Eosinophils are a type of white blood cell that helps protect against parasites.
Eosinophils are small and long. They stick out of the surface of the skin like little spines.
Other key types of white blood cells include:
Neutrophils are more than just white blood cells; they form one of the most important components of our immune system and are one of the most abundant types of white blood cells.
They are responsible for fighting infections. Neutrophil counts fall when we have bacterial infections.
During inflammation, neutrophils migrate from the bloodstream to the site of injury or infection. At the site of the infection, they secrete enzymes that damage the surrounding tissue.
In addition, neutrophils can form extracellular traps (NETs) that trap and kill bacteria. NETs are made up of DNA fibers coated with antimicrobial peptides called defensins.
Eosinophilic granulocytes are another component of our immune system. In healthy people, eosinophils make up about 1% of all white blood cells.
However, during allergic reactions, eosinophilia occurs, and during this reaction, eosinophil counts rise to potentially dangerously high levels.
Basophils are a type of white blood cell that helps fight parasites. Their numbers tend to increase in response to parasitic infections.
Natural Killer Cells
Natural killer cells are cytotoxic lymphocytes that play an important role in natural immunity against tumors and virally infected cells.
NK cells are activated by stress signals, such as those produced during viral infections.
They do not require the previous contact with the target cell, but simply recognize them based on their expression of certain proteins.
Once activated, NK cells release cytokines that stimulate other immune cells to eliminate the target cell.
Dendritic cells are sentinel cells of the immune system. These cells are constantly patrolling the body, looking for signs of infection.
When dendritic cells detect danger signals, such as microbes or cancerous cells, they travel to local lymph nodes where they help turn naive T cells into active effector T cells.
Macrophages are large, phagocytic cells that ingest foreign particles, dead cells, and cellular debris.
They are part of both innate and adaptive immunity. Macrophages are found throughout the body, including in the lungs, spleen, liver, bone marrow, and brain.
Mast cells are tissue-based basophilic granulated cells that contain histamine. Mast cells are found in connective tissues, mucosal membranes, and skin.
They are also present in the gastrointestinal tract, respiratory tract, and genitourinary tract. Mast cells are thought to be involved in allergies and asthma.
White Blood Cell Differentials
When you take a blood test, you’ll get results showing how many of each type of white blood cell are present in your blood.
You might also receive a report showing the percentage of each type of white cell relative to the total amount of white blood cells in the blood.
The differential count provides information about the health of the various types of white blood cells that are present in the blood sample being tested.
For example, a person who develops a fever during a viral illness may have an increase in neutrophils (white blood cells) without a corresponding increase in lymphocytes (white blood cells).
This indicates that the person’s body is trying to fight the virus. However, this response can lead to complications if it continues for too long.
A person who has a high level of neutrophils may develop pneumonia.
This test measures the total number of white blood cells in a given volume of blood. If the total number of white cells in your blood decreases, then there must be fewer than normal numbers of platelets.
Platelet disorders can result from either increased destruction or decreased production of platelets.
The two main causes of thrombocytopenias are bone marrow failure and autoimmune diseases such as lupus erythematosus.
This test is used to determine whether a patient has a bleeding disorder. Bleeding disorders occur when the blood-clotting process does not function normally.
In some cases, patients with bleeding disorders will have low levels of all three blood components: red blood cells, white blood cells, and platelets. Other times, only one component is affected.
Complete Blood Count
A complete blood count (CBC) includes several tests that measure different aspects of your blood. It shows the number of different kinds of cells in your blood and their amounts.
The CBC helps doctors diagnose and treat conditions that affect the blood. Some common reasons why people need a CBC to include:
- To check for anemia, which occurs when there aren’t enough red blood cells in your bloodstream. Anemia can cause weakness, fatigue, dizziness, shortness of breath, headaches, and heart problems.
- To check for leukemia, which is cancer of the blood-forming organs. Leukemia usually starts in the bone marrow but can start anywhere else in the body.
- To check for infection, which is caused by bacteria, viruses, parasites, or other microorganisms. Infection can spread throughout the body and cause symptoms like fever, chills, aches, and pains.
- To check for abnormal growths called tumors. Tumors can grow in almost any organ and can sometimes be benign (not harmful), but they can also become malignant (cancerous).
- To check for immune system deficiencies. Immune system deficiencies can make you more susceptible to infections.
- To check for kidney disease. Kidney disease affects the kidneys’ ability to filter waste products out of the blood. These wastes build up in the blood until they damage the kidneys.
- To check for liver disease. Liver disease can cause many symptoms including abdominal pain, yellowing of the skin or eyes, dark urine, nausea, vomiting, loss of appetite, weight loss, and jaundice.
- To check for thyroid disease. Thyroid disease can cause many symptoms like feeling tired, having trouble concentrating, and swelling around the neck.
- To check for vitamin B12 deficiency. Vitamin B12 deficiency can cause numbness and tingling in the arms and legs, difficulty walking, and memory loss.
- To check for sickle cell traits. Sickle cell trait is a genetic condition that makes it easier for sickled red blood cells to form. People who have this trait may not experience any symptoms.
- To check for iron deficiency. Iron deficiency can lead to fatigue, irritability, poor concentration, muscle cramps, and pale skin.
- To check for folic acid deficiency. Folic acid deficiency can cause nerve problems, seizures, and mental retardation.
- To check for thalassemia. Thalassemia is a group of inherited diseases that are characterized by changes in the structure of hemoglobin. Hemoglobin is a protein found inside red blood cells that carries oxygen from the lungs to the rest of the body. The most common type of thalassemia causes the production of defective hemoglobin molecules. As a result, the red blood cells cannot carry sufficient oxygen to the tissues.
Platelets play a major role in our overall health and wellbeing, and so it is important that you have a good understanding of their basic role and function.
This will offer a more comprehensive understanding of your body, as well as provide early signs if something goes wrong.
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