Platelets are tiniest of the cells circulating in the blood. There role is to help in wound healing and prevent bleeding by forming blood clots , at the site of injury. So with this function, you will realize that both low and high platelets are bad for our bodies. Low platelet means that blood clots will not be easily formed ,and so bleeding will continue ( as in dengue ). The reverse, meaning very high platelet counts , is associated with excessive blood clots leading to obstruction to flow of blood, which is also not good.
Q) What is the normal platelet counts in our bodies ?
A) It varies. It depends on the age.
In adults , normal platelet counts are considered between 1,50,000 to 4,00,000 per microlitre of blood.
It can also be reported as 150 to 400 x 10^9 per litre of blood.
Both of them are same thing – we have microlitre in the first one and per litre in the second one.
Now, in a child say between 2 to 6 years of age, normal platelet counts are considered between 200 to 490
per litre of blood.
So, now you understand that platelet count of 180 x 10^9 will be considered normal in a adult , whereas the
same counts in a 3 year old child would mean that platelet counts are slightly below the normal for that
Q) Why do we have different normal ranges for adults ,babies etc ? Why are they not the same ?
A) These ranges are based on studies conducted throughout the world. Based on data available, different ranges
were statistically decided for different age groups and used accordingly.
Q) What do platelets look like ?
A) Platelets are very tiny – around 5 microns in diameter and thus can only be viewed on a microscope.
The attached image below shows what a platelet looks like.
The brownish oval cells are Red blood cells and the small purplish dots are the platelets. Please note that platelets are normally not purplish in colour. We have stained the blood , and platelets have a purplish hue in this stain.
Q) What is thrombocytopenia and thrombocytosis ?
A) Thrombocytopenia means low platelet counts and thrombocytosis means high platelet counts.
So,if you know what is the normal range of platelets for that particular age group, you would know as to whether the patient has thrombocytopenia or thrombocytosis. This is generally mentioned on the extreme right of laboratory reports.
So now let us analyze one random laboratory report as shown below :
In this report, Platelets are written as PLT.
Patients value is 45 , whereas the reference range for that particular age group is 140 to 440 .
This means that the patient has a low platelet count or Thrombocytopenia.
Also look at the reference units that the lab is following – It is in thousands / c.mm which is the same as 10^9 per litre .
Thats it. In my next blog I will write about thrombocytopenia .