If blood samples are to be stored frozen for some time till the analysis of blood glucose levels .. is it accurate to use frozen serum or it must be stored in grey tubes ? For how long ? And does it need any processing in the grey vacutainers before storage?
I think it is possible to store up to 42 days before blood transfusion, although there is sufficient evidence that RBCs undergo adverse changes during storage, studies evaluating results regarding storage time report conflicting results.
Depending on the assay, your serum might be fine if it did not go through several freeze-thaw cycles. However since you are only talking about blood glucose, can't you just use one drop of fresh blood and a glucometer to obtain this value before storage?
@Marie Mortreux No, it is not only about glucose ... there are another tests to be done for the same samples
You should add the assays to your question so we can advise you appropriately
@Marie Mortreux serum LDL, HDL, TC, TG, insulin, creatinine, albumin and bilirubin will be measured in addition.
I think 3 months should be fine for insulin and lipids (I've done it before). However, the quality of your plasma might depends on the storage conditions. If you're not sure of the quality of your samples and if you know what to expect (roughly) for your controls, the best thing is probably to try to run some tests on some of them to check their quality, before running all your experiment?
My dear, three month is more Difficult because storage fresh blood will be destruction red blood cell and acctuly effect on tests so should be storage serum in deep freerz for long time