Dear Hadjkacem Basma,

if I understand your question correctly, you want to know why platelet units cannot be stored in a refrigerator at 4°C. The answer is quite simple: The platelets loose their function. A couple of explanations for this can be found in literature, however, a simple test can show this phenomenon: Just store a bag of platelets at 4°C overnight, and look at swirling prior to and after storage: The swirling will be gone. So will platelet function (you could do aggregation tests before and after storage).

Some mechanisms are explained in this recent publication.

Dear Hadjkacem Basma,

if I understand your question correctly, you want to know why platelet units cannot be stored in a refrigerator at 4°C. The answer is quite simple: The platelets loose their function. A couple of explanations for this can be found in literature, however, a simple test can show this phenomenon: Just store a bag of platelets at 4°C overnight, and look at swirling prior to and after storage: The swirling will be gone. So will platelet function (you could do aggregation tests before and after storage).

Some mechanisms are explained in this recent publication.

Thank you Julian for your answer.

You forgot to attach the recent publication. 

Actually I did attach a link. However, it was gone this morning. I have inserted it again, this time only the pubmed abstract link. Hopefully this does not break copyright laws.

Another group has recently published data ohne refrigerated platelets and they think that platelets are functioning well after cold storage: Look for Pidcoke HF, cold, storage, platelets, function. I am just reading those.

http://www.ncbi.nlm.nih.gov/pubmed/19932055

Or you could have a look at this paper - a bit old, but Hoffmeister is an expert in the field!

http://ac.els-cdn.com/S0092867402012539/1-s2.0-S0092867402012539-main.pdf?_tid=55043bd8-5ab1-11e4-833a-00000aab0f01&acdnat=1414068021_f0aaf900e25852fc668e0f5b0417f66f

Dear Hadjkacem Basma: I agree with Julian. Cold activates platelets and they loose their granules contain thus favoring aggregation and release. This was demonstrated testing for p-Selectin, before and after cooling. 

La durée de stockage acceptée pour les plaquettes est de 5 jours et jusqu’à 7 jours à une température comprise entre 20 et 24°C sous agitation permanente. toute diminution ou augmentation de la température entraînera une altération de la fonction plaquettaire (agrégation, activation...)

Hi Basma,

 AS main problem, cold storage of platelets leads to clustering of alpha subunits of glycoprotein Ib (GPIbalpha)) on the platelet surface, its  Desialylation  that accelerating platelet clearance as well as increased rate of apoptosis.

Regs

Mehran