Platelets

Platelets help maintain blood in the vessels.

When injury occurs, they adhere to the blood vessel walls, clump together and plug the hole. Many patients can present with platelet deficiency, for example after chemotherapy, and run the risk of extensive blood loss.

Blood platelet transfusion is therefore crucial.

What is the process? 

Platelets are isolated using an automatic cell separator machine, which selectively collects them from the blood. Once the blood has passed through the machine, it is returned to the donor in a closed-loop system.

These machines are so efficient that there is only a slight reduction in the donor’s platelet count. This reduction is of no significance, because bone marrow produces 100 to 200 million platelets every minute. Harvested platelets are therefore replaced within a few days.

When the blood is drawn, several samples are collected for various tests, including a complete blood count which is analyzed immediately. This test allows platelet donor monitoring and also provides important data for calibrating the cell separator machine.

There is therefore just a single needle-prick in one arm.

Platelet donation (blood tests, collection and return after donation) takes around 2 hours altogether.

 

 

What are the medical requirements for platelet donation?

The health questionnaire which is completed for blood donation is also valid for platelet donation.

Certain conditions contraindicate platelet donation. In particular, a dental procedure (including scaling) in the 72 hours preceding platelet donation, or a temperature above 38°C in the last four weeks.

Some medicines which inhibit platelet function and therefore make them useless for transfusion should equally be avoided. These include all forms of Aspirin and non-steroidal anti-inflammatories such as Ponstan, Felden, Tilcotil, Brufen, Indocid and Voltarene to mention just a few. In contrast, Panadol (paracetamol) can be taken providing that it is not combined with any of the above medicines.

The usual eligibility testing for blood donation is used for platelet donation, and includes screening for syphilis, hepatitis B and C, and the HIV virus.

 

What are the indications for platelet transfusion therapy? 

The amount collected during donation, at no risk to the donor, is enough to prepare one or two therapy units sufficient for platelet transfusion in patients with the following conditions:

  • Leukemia : when a patient has leukemia, their bone marrow is overrun by abnormal cells which prevent healthy cells being produced, in particular platelets.
  • Cancer : where treatment needs chemotherapy, this is so powerful that is destroys not only the cancerous cells but also many healthy cells including platelets.
  • Aplasia : this is reduction or cessation of healthy blood cell production by the bone marrow. It could be a condition of the bone marrow itself (idiopathic medullary aplasia) or the result of chemo- and/or radiotherapy (in cases of bone marrow grafts, among others). Until the bone marrow is once again functioning normally, the patient needs frequent platelet transfusions.
  • Extensive blood loss or patient undergoing large-scale transfusions.

In order for the receiver to avoid certain immunizations, the platelet donor can be matched according to their compatibility or semi-compatibility with the receiver, particularly using the HLA system*.

*HLA System (Human Leukocyte Antigens): system of genetic markers carried by the white blood cells and present in most body tissues. In many cases, matching of the HLA system between donor and receiver should be observed.

 

Last update : 08/08/2018