Risk minimization in transfusion transmitted infection in Hong Kong

Abstract

Safe blood supply is vital in modern healthcare system as clinical blood transfusion remains a common and life-saving treatment modality. Although there have been many advances to mitigate transfusion transmitted infection risk, people remain concerned about its safety. This is because zero-risk could not be attained due to the limitations of the current testing technologies in the detection of window period donations, and the ongoing threat from emerging infection when no routine blood donation screening test is available.

After following the best international practice to secure blood safety, the Blood Transfusion Service in Hong Kong has reduced its transfusion risk significantly in the last two decades. It is observed from this study that both the number and prevalence of HBsAg positive and anti-HCV positive donors are decreasing over the years. Although there are still donor non-compliance, the estimated residual risk of transfusion transmitted HIV infection has been reduced from 1 in 1,000,000 units to 1 in 2,400,000 units, after the introduction of nucleic acid testing (NAT). Donor follow-up study revealed 40.91% of anti-HIV positive donors with a history of male-to-male sexual activities as major risk factor.

Pilot and prospective NAT studies identified up to 0.1% of blood donors and general population with occult hepatitis B infection (OBI) in Hong Kong. Surveillance study after the local implementation of HBV NAT revealed the prevalence of OBI in 0.023% and 0.030% of the new and previous donors respectively. As a result, the estimated residual risk of HBV through transfusion decreased from 1:20,000 to 1:55,000. Besides, the infectivity of blood components donated from the donor with OBI was supported by identifying a transfusion recipient with HBV with 95% sequence homology with the donor HBV in the lookback study.

Studies from bacterial surveillance programme, donor skin disinfection, selection of chlorhexidine /alcohol as skin disinfectant and the introduction of diversion pouch have made the most significant contributions to risk reduction in the transfusion transmitted bacterial sepsis in Hong Kong. It was observed that the bacterial contamination rate of platelet concentrates decreased from 7.45 per 10,000 units in 1998 to 0.54 in 2015. No transmission was reported following the platelet transfusion. On the other hand, some donors were found to have asymptomatic bacteraemia. Strept. bovis and related species were the most important, as donor follow-up reviewed the presence of colonic polyps and even carcinoma in 50% of the cases.

Lastly, one confirmed (Dengue fever) and two (hepatitis E and varicella-zoster) potentially transfusion transmitted infections were observed during the course of this study. Although they are not normally parenterally transmitted, viraemia was detected in the donated units, making them infectious.

In summary, studies on the implementation of risk reduction measures confirmed substantial blood safety improvement in Hong Kong. Emerging infections became an ongoing risk towards the safety of blood supply and non-testing approaches, such as donor eligibility, donor policy, and pathogen reduction technologies should be explored and evaluated as per their suitability of local application.