Endpoints in clinical trials on transfusion requirements: the need for a structured approach

Effectiveness of the scheduled transfusion strategy for factor V deficiency with platelet dysfunction during coronary artery surgery

BACKGROUND

Factor V deficiency is a rare disease, with an incidence of one in a million. Symptoms are mostly scant, and it is often diagnosed by the presence of an abnormality on PT-INR or APTT. In addition, no established therapy exists and platelet dysfunction is seldom found to be concomitant with this disease CASE PRESENTATION: A 64-year-old man who had both factor V deficiency and platelet dysfunction had angina in the past year. Coronary surgery was required, and we successfully performed coronary artery bypass grafting under strategic planned platelet transfusion with additional adequate cryoprecipitates transfusion. No perioperative problems nor any postoperative major bleeding issues were observed. The postoperative course was also uneventful.

CONCLUSION

Strategic planned platelet transfusion with the additional transfusion of an adequate amount of cryoprecipitates is thus considered to be feasible for cases presenting with factor V deficiency and platelet dysfunction.

Hepatitis B virus DNA-positive, hepatitis B surface antigen-negative blood donations intercepted by anti-hepatitis B core antigen testing: the Canadian Blood Services experience

BACKGROUND

The benefit of introducing anti-hepatitis B core antigen (HBc) screening for intercepting potentially infectious donations missed by hepatitis B surface antigen (HBsAg) screening in Canada was studied.

STUDY DESIGN AND METHODS

Anti-HBc testing of all donations was implemented in April 2005, along with antibody to hepatitis B surface antigen (anti-HBs) and hepatitis B virus (HBV) DNA supplemental testing of anti-HBc repeat-reactive, HBsAg-negative donations. The proportion of potentially infectious donations intercepted by anti-HBc over the initial 18 months of testing was calculated based on three assumptions relating infectivity of HBV DNA-positive units to anti-HBs levels. Lookback was conducted for all DNA-positive donations.

RESULTS

Of 493,344 donors, 5,585 (1.13%) were repeat-reactive for the presence of anti-HBc, with 29 (0.52%) being HBV DNA-positive and HBsAg-negative. The proportion of potentially infectious donations intercepted by anti-HBc screening was 1 in 17,800 if all HBV DNA-positive donations were infectious, 1 in 26,900 if infectivity was limited to donations with an anti-HBs level of not more than 100 mIU per mL, and 1 in 69,300 if only donations with undetectable anti-HBs were infectious. For 279 components in the lookback study, no traced recipients were HBsAg-positive and 7 recipients were anti-HBc-reactive in association with 4 donors, 3 of whom had an anti-HBs level of more than 100 mIU per mL and 1 of whom had a level of 61 mIU per mL.

CONCLUSION

Implementation of anti-HBc screening reduced the risk of transfusing potentially infectious units by at least as much as had been expected based on the literature. The lookback did not provide proof of transfusion transmission of HBV from HBV DNA-positive, anti-HBc-reactive, HBsAg-negative donors but it did not establish lack of transmission either.

Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services

BACKGROUND

New testing methods such as nucleic acid amplification testing (NAT) and chemiluminescent serologic assays have been introduced, more precise estimates for infectious window periods are available, and a new method for estimating the residual risk (RR) of transfusion-transmitted infections (TTIs) has been developed. Thus, available RR estimates for Canada need to be updated.

STUDY DESIGN AND METHODS

Incidence rates for known TTI markers were determined for all allogeneic whole-blood donations made to Canadian Blood Services between 2001 and 2005; they were derived from NAT conversions or seroconversions of repeat donors with at least two donations in a 3-year period. RR estimates for human immunodeficiency virus (HIV)-1 and hepatitis C virus (HCV) derived from the classical incidence/window-period model were compared to those obtained by the new method that estimates incidence from NAT-positive, antibody-negative donations (NAT-yield cases) from all donors divided by person-years.

RESULTS

With the classical method, the RR of HIV (1 per 7.8 million donations) and HCV (1 per 2.3 million) were low; HBV RR was higher (1 per 153,000). HCV RR was significantly lower when estimated with the new method (1 per 13 million). Eleven HCV NAT-yield cases were predicted by applying the classical method to our seroconversion data but only 2 were observed (p = 0.011). Observed HIV-1 NAT-yield cases (n = 1) matched those predicted (n = 0.7).

CONCLUSION

New tests have reduced an already low risk of TTI in Canada. HCV RR estimates by two different methods differed but both were low.

Hepatitis B virus blood screening: unfinished agendas

The risk of transfusion-transmitted hepatitis B virus (TTHBV) has been steadily reduced through the use of volunteer donors, enhanced donor questioning, and increasingly sensitive hepatitis B surface antigen (HBsAg) tests. In a few countries, screening by antibody to hepatitis B core antigen (anti-HBc) and/or hepatitis B virus (HBV) nucleic acid amplification tests (NAT) has also been introduced. Nevertheless, the risk of TTHBV in most countries is higher than the risk of either human immunodeficiency virus-1 (HIV-1) or hepatitis C virus (HCV). HBV screening practices vary both in terms of the markers screened and the tests employed, and are often dependent on a country's healthcare resources. Anti-HBc screening could be employed as an additional safety feature in HBV low-prevalence countries, but would lead to the rejection of a high percentage of otherwise acceptable donations in HBV moderate- and high-prevalence countries. It has been argued that only individual-donor HBV NAT testing would substantially reduce the risk of TTHBV beyond that achieved by the most sensitive HBsAg tests. However, studies from countries with low, moderate and high HBV prevalence have demonstrated NAT yield from window period- and late stage HBV-infected donors, even using minipool testing following the most sensitive HBsAg tests.