Platelets are small, granulated bodies of two to four micro meters in diameter, present in the blood along with other cellular components. About 300,000 per micro liters platelets are present in the circulating blood. Their normal half life is about four days.

Platelet production is being carried out in the bone marrow, where the megakaryocytes, giant cells form platelets by pinching off bits of cytoplasm and extruding them into the circulation. Certain colony stimulating factors regulate the platelet production. Out of these, a newly cloned factor is the thrombopoeitin, which facilitates megakarycyte maturation.

Between 65 to 70% of the platelets extruded from the bone marrow circulates in the blood, but the remainders are mostly in the spleen. So, splenectomy causes increase in the circulating blood platelet count (thrombocytosis).

At the event of blood vessel wall injury platelets adhere to the exposed collagen, laminin and von Willebrand factor in the wall via integrins on the platelet surface. Unlike platelet aggregation, the process of platelet adhesion is not an active process. It does not require any platelet metabolic activity. However, when the platelets bind to collagen, it initiates platelet activation, necessary for platelet aggregation. Activation of the platelets can also be produced by ADP and thrombin. By changing their shape, putting out pseudopodia and discharging granules, the platelets stick to other platelets. This process is known as platelet aggregation. It is suggested that the process of aggregation can also be fostered by the platelet activating factor (PAF), a cytokine secreted by neutrophils, monocytes and platelets themselves.

Decreased platelets result in deficient clot retraction and poor constriction of ruptured vessels. It results in the clinical syndrome commonly called as thrombocytopenic purpura, which is characterized by easy bruisability and multiple subcutaneous hemorrhages. Purpura may occur in the cases where the count is normal but the circulating platelets are abnormal (thrombasthenic purpura).

Here I would like to discuss a remarkable product Impact-R which is widely used for the assessment quantity and functionality of the blood platelets. Abnormal functioning platelets are detected with the help of Impact-R, which would otherwise lead to serious hemostatic abnormalities.

Blood cells are produced in the bone marrow. The three main components of blood are the red blood cells which carry oxygen, white blood cells or leukocytes which fight infection and platelets also called thrombocytes which assist in the formation of blood clot.

When a blood vessel is damaged platelets adhere to the surface of damaged vessel wall and release chemicals. The chemicals attract more platelets as well as red blood cells in order to form a clot or thrombus. As the clot grows the blood vessel narrows, thereby decreasing the blood loss. This process is called coagulation.

Normal platelet counts are in the range of 150, 000 to 350, 000 platelets per micro liter. Thrombocytopenia or low blood platelets are the disorders in which there are not enough platelets in the blood. When the platelet count is decreased the body is unable to form blood clots and is therefore unable to control the bleeding. Bruising and bleeding can occur from relatively little trauma. When the platelets count gets below 10, 000 platelets per micro liter, bleeding can develop even without significant trauma.

Chemotherapy induced thrombocytopenia is a disorder that develops as an adverse effect of chemotherapy. Cancer drugs not only kill cancer cells, they can also damage the platelet forming cells in the bone marrow. The severity of this disorder depends on the type of chemotherapy and the duration of treatment. Fortunately chemotherapy induced thrombocytopenia or low blood platelets can be managed with platelet transfusions, additional medications such as blood cell growth factors or with blood stem cell transplants.

Other common causes of thrombocytopenia or low blood platelets are ITP (immune thrombocytopenic purpura) and heparin induced thrombocytopenia. In immune thrombocytopenic purpura, anti platelet antibodies coat the platelets and destroy them, while heparin induced thrombocytopenia is caused by the formation of abnormal antibodies that activates platelets.

Impact-R has evolved as a blessing in disguise for the thrombocytopenia hit populations as it provides a very effective screening test for the timely detection of the patients suffering from thrombocytopenia. It has markedly decreased the morbidity and mortality associated with this disorder.

Al l four serotypes of dengue viruses are well known for taking the toll of healthcare facilities all over the world. Sporadic cases of dengue fever have scattered distribution including US, Mexico, Puerto Rico and you name any place. Mankind has also seen a multitude of dengue fever epidemics especially in 1979 and 1980 when they swept Asia, Africa and North America. Now, once again dengue has hit a gorgeous land of Pakistan, especially the Punjab Province.

As already mentioned dengue virus has four serotypes (dengue 1-4), having Aedes aegypti as their principal vector. Aedes aegypti is commonly known as the ‘Tiger mosquito’ that bites during the day as compared to the Anopheles species (causing malaria) that usually bite at night. Aedes aegypti is also a vector for the Yellow fever virus and the Chikungunya virus. It typically breeds near human habitation, using relatively fresh water from the sources like vases, jars, containers etc. All the four serotypes cause the same type of disease in the human beings.

The classic dengue fever has an incubation period of 2-7 days, and patient experiences sudden onset of fever, headache, retro orbital pain, severe back pain associated with myalgias. Due to these symptoms, the fever has been given the name of ‘Break Bone fever’. Other associated features of this disease may be anorexia, nausea, vomiting, and appearance of maculopapular rash all over the body, scleral injection and adenopathy. Even epistaxis and petechiae may appear in an uncomplicated disease. Laboratory findings are leucopenia, thrombocytopenia and in some cases serum aminotransferases may be elevated.

Thrombocytopenia is an important diagnostic finding in the cases of dengue fever that occurs due;

• Direct infection of bone marrow megakaryocytes.
• Immunological shortened platelet survival.
• A more complicated form of infection is the Dengue Hemorrhagic Fever/Dengue Shock Syndrome. It can occur in two forms;
• Re infection of an individual by a heterologous strain of the dengue virus previously infected from the dengue virus.
• Even classic dengue fever can progress to dengue hemorrhagic fever.

Dengue hemorrhagic fever is characterized by overt bleeding in the absence of underlying causes, increased bleeding tendency (can be appreciated by tourniquet test or presence of petechiae). In mild cases restlessness, lethargy, thrombocytopenia (platelets < 100,000 per micro liters) and hemoconcentration appears usually 2-5 days after classic dengue fever. In severe cases there is frank shock, low pulse pressure, cyanosis, hepatomegaly, pleural effusion and ascites. Individuals usually bleed profusely in some severe cases. Most of the people usually respond well on supportive therapy, however some need platelet transfusions.

Here comes the role of Impact-R which can be used for clinical diagnosis of dengue fever by confirming the presence of thrombocytopenia in an individual. Moreover, it also helps determining the function of the platelets being infused in the patients. Stored platelets are usually used in the patients for the treatment of dengue hemorrhagic fever and their functional assessment is done by Impact-R.

Patients with end stage renal disease suffer from a multitude of haemostatic disorders. This bleeding is mainly due to impaired platelet function present in the uremic patients. Both the platelets adhesion (platelet vessel wall interaction) and the aggregation are affected resulting in bleeding diathesis. Studies have shown that haemodialysis of these patients in time results in the decreased hemorrhagic episodes.

Impact-R is can be utilized in these cases for the early detection of platelet function abnormalities, and can help in reducing the morbidity and mortality associated with hemorrhage in end stage renal disease.

Before discussing the causes of low blood platelets or thrombocytopenia, I feel necessary to mention the grave consequences associated with low blood platelets. The dominant features of thrombocytopenia include petechial cutaneous bleeding, intracranial bleeding and oozing from mucosal surfaces.

Causes can be divided into three main groups;

• Decreased production
• Increased destruction
• Un replaced loss or dilution of platelets

The characteristic findings of thrombocytopenia are decreased platelet count and prolonged bleeding time. Bone marrow aspiration is helpful in the cases of thrombocytopenia. It reveals decreased megakaryocytes (immature form of platelets) when caused by decreased platelet production and increased megakaryocytes when caused by increased platelet destruction.

Now I would like to discuss few common causes of low blood platelets;

• Irradiation, exposure to drugs or chemical causes decreased production of the platelets.
• Acute leukemia in which there is decreased platelet production due to replacement of bone marrow by blast cells.
• Myelophthisis results in low blood platelets because the bone marrow is replaced by tumor cells.
• Aplastic anemia can also be the cause of low blood platelets. It may be caused by exposure to toxic agents like benzene or due to autoimmune destruction by cytotoxic T cells.
• Circulating blood platelets are lost or destroyed when they are sequestered by spleen, thus decreasing the blood platelet count.
• Dilution of platelets occurs in multiple transfusions, where there is relatively deficiency of platelets and thus low blood platelets.
• Disseminated intravascular coagulation, commonly known as consumptive coagulopathy results in consumption of almost all the platelets in the blood.
• Low blood platelets can be secondary to other disease such as acquired immunodeficiency syndrome or systemic lupus erythematosus.
• Immune thrombocytopenic purpura is a very common autoimmune disorder of the platelets occurring due to formation of anti platelet antibodies in the blood, which damage the platelets and decreases their count.

All the above mentioned causes of thrombocytopenia can be diagnosed well before time by the use of Impact-R platelet analyzer. This kit uses the very basic principles of platelet aggregation and adhesion and can be used to screen the cases of thrombocytopenia due to any cause.

Blood platelets commonly called megakaryocytes are one of the three tiny cellular components of the blood which helps in the stoppage of bleeding.. Other cellular components of blood are the red blood cells and white blood cells. All the cellular components bathe in the plasma.

Nearly half a billion blood platelets are being formed in the bone marrow every day. These play a primary role in the formation of blood clot. Here I would like to define the two common terms related to the platelet plug formation when the blood vessel in injured.

*  Adhesion means sticking of blood platelets with the wall of the bleeding vessel.

*  Aggregation means sticking of the platelets with each other.

Normally, in the circulating blood, platelets keep on flowing without any adhesion or aggregation. However, injury to the wall of blood vessel is the point when blood platelets start clinging to the injured part of the vessel wall. At the same time the platelets aggregate with one another and completely seal the opening which helps in arresting the bleeding from the specific site. We call these aggregates as ‘haemostatic plugs’.

Blood platelets can also be activated in the presence of atherosclerosis where the disease itself damages the intimal layer of the blood vessel. So, platelets cling to this damaged layer of the vessel wall and results in the formation of platelet plug by the process of adhesion and aggregation. Eventually thrombus is formed when the coagulation factors come into play. So, blood platelets are responsible for most of the cardiovascular and cerebrovascular events occurring in the human body.

Anti platelets drugs are used as blood thinners in the high risk patients. Their basic role is to decrease the activity of the platelets in the circulating blood.

While using anti platelet drugs, role of Impact-R cannot be ignored because it monitors the response to the anti platelet drugs with high accuracy and is very sensitive in all such tests. So, over treatment or under treatment can be easily detected and dealt with accordingly. Presently it is being used for the research purposes but can be used clinically also.