Bioreactive substances including cytokines and lipids accumulate during storage of red blood cells (RBCs) but their clinical importance is uncertain. The goal of this study was to evaluate the effect of stored RBC supernatant on neutrophil activity in vitro. Packed RBCs (PRBCs) were collected and divided into two aliquots, one leukodepleted and the other nonleukodepleted. Plasma supernatant from PRBCs were collected on days 1, 8, 15, 29 and 35 and its effect on neutrophil expression of CD11b, CD16 and oxidative burst was measured by flow cytometry. Levels of tumour necrosis factor alpha (TNFα) and interleukin‐8 (IL8) were also measured. The supernatant from PRBC units stored for greater than 15 days activated and primed neutrophils as evidenced by an increase CD11b and CD16 expression and oxidative burst. The greatest effect was seen in the oldest concentrates (35‐day‐old) (P < 0.008). Leukodepletion abrogated the effects of stored supernatant on CD11b and CD16 expression (P < 0.02) but did not reduce priming of the neutrophil oxidative burst (P > 0.1). Very low levels of IL8 and TNFα were detected in stored supernatants. Stored PRBC supernatant contains substances which directly enhance neutrophil expression of adhesion protein CD11b, CD16 and prime neutrophil oxidative burst. The exceedingly low level of IL8 and TNFα found in this study suggests that other factors may play a more important role in neutrophil priming and activation.

The most common methods used for evaluation of the haematopoietic stem cell content of peripheral blood apheresis products are the colony forming cell assay and the enumeration of CD34+ cells by flow cytometry. The Canadian Apheresis Group and the Canadian Bone Marrow Transplant Group established a multicentre study to compare the reproducibility of colony forming cell assays and CD34+ enumeration by flow cytometry in six transplant centres routinely performing haematopoietic stem cell apheresis. Over a 5-month period in 1996, 31 fresh apheresis samples were shipped by overnight courier for testing at six centres to perform CD34+ enumeration by flow cytometry and clonogenic assays. The mean coefficient of variation and range for the following assays were: cell count 36% (2.6-148%), CFU-GM 82% (46-123%), CD34+ absolute/kg 60% (14-174%) and CD34+ per cent 42% (12-84%). The wide variation in cell count in this pilot study highlights the difficulties related to provision of samples for quality assessment programmes. Results showed poor interinstitutional reproducibility even among selected samples with similar cell counts for both CFC and CD34+ assays demonstrating the need for development and implementation of an interinstitutional quality assurance programme for haematopoietic stem cell assessment. Provision of a reliable source of testing material will be a necessary next step.