Modern whole blood collecting systems and additive solutions allow for storage of RBC up to 42 or 49 days with acceptable in vivo survival rates [8
However, many adverse changes in stored RBCs may impair the oxygen transport and delivery capacity of the transfused RBCs, like the loss of S-nitrosohaemoglobin [10
] or of 2,3-DPG [11
]. These alterations are known to occur during processing and storage of RBCs and are related to storage conditions such as temperature, pH, and chemical composition of the environment. Approved quality assessments of RBCs at the end of their storage duration comprise the HB content, the rate of haemolysis and the residual leucocyte count [12
]. For our study we extended these quality control parameters as described above.
The blood collection and conservation systems have been steadily optimised, taking many of these aspects into account. Some factors may influence the quality of RBCs already during the collection process itself, like an overwhelming concentration of anticoagulant during the first minutes of blood donation or a variable whole blood-to-anticoagulant ratio [4
]. During a conventional donation procedure, whole blood flows in a bag previously filled with a prefixed volume of CPD anticoagulant solution. The targeted ratio of 7:1 between blood and solution is achieved only at the end of the donation. Therefore, the RBCs are initially exposed to a high concentration of anticoagulant and an accordingly low pH for a few minutes. This may result in a ‘lesion of collection’. For RBCs being held in ACD for up to 30 min, it has been shown that their in vitro quality and their in vivo 24-hour survival rates are impaired [1
The ABC may improve the quality of collected RBCs by continuously adding a metered volume of CPD from a satellite bag into the draw line during the whole blood donation [6
]. Limited data about ABC have been reported since 2003. These were restricted to processing data [13
] or, if additional quality control analyses of RBCs were performed, were not directly compared with results of already validated systems [15
]. A recently published controlled study focused on quality of RBC concentrates of sickle trait donors, but the number of donations is insufficient to infer on the quality of ABC under normal conditions [17
]. We present the first study comparing the ABC device with an approved standard whole blood collection system, which was otherwise virtually identical and manufactured by the same company. The comparability of the two groups is further guaranteed by the equal predonation HB values and the crossover design.
When comparing the performance of CONV and ABC methods for blood donation and processing, both showed identical values for donation and filtration times as well as for loss of volume by filtration. Although the number of residual WBCs in ABC is higher than in CONV, all products show WBC counts clearly below 106 per unit. The higher volume of the ABC donations, partially due to the slightly higher volume of CPD anticoagulant, persists after filtration. The lower standard deviations additionally indicate a more standardised collection volume with ABC compared to CONV. This may be the result of continuously weighing a resting instead of an agitating bag. However, this does not result in a higher standardisation of the final products (RBC units and plasma), as measured by the standard deviations of the quality control data during storage (table ).
All quality control parameters meet the current Swiss and European standards. The majority of the haematological and chemical changes observed during storage of RBCs obtained by ABC or CONV are comparable. We only observed some minor differences in several parameters. Although the identical centrifugation and separation protocols of ABC and CONV lead to identical total HB contents in the RBC units, an increase of MCV resulted in an increased HC and a decreased MCHC in ABC. The latter has also been reported for RBCs derived from erythroplasmapheresis with a single needle apheresis device [6
]. With respect to the discordant course of K+
concentrations, enhanced physical changes in the RBC membrane collected with ABC have to be suggested, e.g. by an impaired activity of the Na-K-ATPase. Additionally, we observed higher glucose consumption and corresponding increased lactate concentration between day 1 and 28 in RBCs collected by ABC. These differences were too small to result in significantly different pH values, and disappeared until day 42. More in-depth in vitro analyses (such as 2,3-DPG, rheological parameters, or even proteomics) and clinical outcome parameters may be included in future studies.
Taken together our results revealed the ABC device to be suitable for whole blood collection. The quality of the obtained RBCs is comparable to that of products gained by conventional whole blood donation methods and meets the current Swiss and European standards. Avoiding the citrate shock by maintaining a correct and constant whole blood-to-anticoagulant ratio during donation with the described method at its current stage of development did not improve the investigated RBC storage quality parameters.