Serological screening for cytomegalovirus in a leucodepleted blood supply: A systematic review

Background and Objectives Cytomegalovirus (CMV) causes harm in at‐risk populations. Selection of seronegative donors has been used to prevent transmission. Leucodepletion reduces the potential for CMV transmission; however, the residual risk is uncertain, leading to variability in practice. This study systematically reviews the risk of CMV transmission in leucodepleted blood products compared to seronegative blood products. Materials and Methods A systematic review identified comparative studies of CMV infection rates following transfusion of leucodepleted blood from CMV‐negative or unselected donors. Preclinical studies on blood product CMV transmission, reported cases and studies that informed population risk were also reviewed. Meta‐analysis was performed on comparative studies. Results There was no difference in the rate of infection following transfusion of leucodepleted cellular products with or without donor CMV seronegativity selection, with a relative risk of 1.21 (95% confidence interval [CI]: 0.42–3.49). No confirmed cases of CMV transmission were found. Preclinical studies showed a significant reduction in transmissible virus with leucodepletion, although no threshold could be defined. Cell‐free CMV is not removed by filtration, and although it may remain a potential source of infection, there was no evidence of transmission through plasma, possibly due to detectable virus not reflecting intact transmissible virus. Conclusion Selecting CMV‐seronegative donors did not reduce the risk of transmission when transfusing leucodepleted blood products because of the high efficiency of filters in removing transmissible cellular virus. This finding suggests CMV donor negative selection does not substantially contribute to donor safety.