The AABB standards state5.1.6.5.1  A unique identification shall be affixed by the collecting or pooling facility to each unit of blood, blood component, and attached containers, or a tissue or lot. This identification shall not be obscured, altered, or removed by facilities that subsequently handle the unit.

If I understand this correctly this means that the original DIN of all received components must not be over written. When reconstituting PRBC's for exchange transfusion, ISBT guidance allows you to either assign your own facility DIN or retain the DIN from the original PRBC unit. If you issued your own DIN does this standard mean you must still show the original DIN? Could this not cause confusion with medical staff during checking as to why 2 DIN's are displayed? If you retained the original DIN, the product code would need to change and the expiry date, is it acceptable to just cover over these portions of the original label with the new parts of the label? (product code and description and expiry date) Leaving the original DIN and blood group visible on the label? 

My hospital is not AABB but I will put in my 2 cents for what it is worth. The way I read this:

The collecting/pooling facility will put a DIN on the product. The receiving facility will not change, alter, or remove the number (on that bag). Reading between the lines if you take those units and combine them in a different way with a NEW number, in a new bag, you are not altering the numbers on the original bags. You have a new bag with a new number and the next facility (should there be one) should not change your new number. Your computer system should be able to retain the original product numbers under the new facility number for posterity. You can locate who received either original number in the pool should there be a lookback in the future.

It might depend on your computer system. Can you print a ISBT label with the new facility number? I would think that is the only number you would need on the new created unit. If you have several numbers on the bag it is going to confuse the nurses at the bedside and we don't need to confuse them. I do remember back in the olden days before computers when we made exchange blood, the bag and paperwork had both the plasma and RBC numbers on it because that was the only way we could do it and keep up with the DIN.

We pool large quantities of plasma for Therapeutic Plasma Exchange. We just use the newly created ISBT facility number on our bag and paperwork. We have never been dinged for this.

I hope this information helps in regards to DIN on collected or pooled products. Per US Consensus Standard, 
the DIN should remain that of the collection facility unless the product is pooled. 

If the product is pooled, a unique new pool number shall be assigned by the pooling facility. This product shall 
be given a new Donation Identification Number (DIN) and not use a DIN from one of the units in the pool. The new 
DIN shall have the Facility Identification Number of the pooling facility.  

And below DIN information is excerpted from the US Consensus Standard v3.0.0 - 7.8.2.2.
Some computer systems treat reconstituted red cells as a pooled product; others do not. The Donation Identification Number (DIN) 
can either be a newly assigned Pool Number (for those systems that treat the product as a pooled product) or that of the RBC 
(for those systems that do not treat it as a pooled product). The text name and location of the facility that appears beneath the 
DIN shall correspond to the Facility Identification Number within the DIN. That means, if the original DIN of the red blood cells 
is used, the name beneath the DIN shall correspond to the collection facility. If a new pool number is assigned to the product, the DIN 
shall have the Facility Identification Number of the pooling facility, and the name beneath the DIN shall be that of the 
pooling facility. Regardless of which method is chosen, traceability of both the red blood cells and the plasma shall be assured. 
The DIN of the plasma must be associated with the DIN of the final product in the facility records. 

Our system does not allow us to pool across product types, so we treat a reconstituted whole blood unit as two units (RBC and plasma) in one bag.  We label with both product codes and both DINs.