Age of blood in inventory at a large tertiary care hospital

This major tertiary care centre transfers over 1000 red cell units monthly. Units are rotated as part of inventory management to ensure minimum wastage. In 1998, the expiration date of AS3 red cells was extended from 35 to 42 days, potentially affecting inventory.

The average age of the red cell units in inventory on any given day was evaluated to determine whether the extended expiration date would affect blood availability and to determine the feasibility of using blood at different ages for various purposes. Over a 6-month duration, 20 days were selected for review: units were categorized according to ABO group and Rh type and then analysed for age within certain categories.

The average age of the blood in inventory was 1 to 2 weeks. The probability of having units less than 1-week old was highest for Group O and zero for Group B Rh(+) and Group AB Rh(+). More than 60% of the O Rh(-) blood was older than 28 days.

The age of units in inventory varies with respect to ABO group, Rh type and weekday. In practice, the stock rarely reaches 42 days of age. Future studies on the effects of age of blood on patient outcome must consider the logistics of supply and the availability of blood of each group. Transfusion of large numbers of units of the same age and of a specific blood group and type may not always be possible.