A novel approach to detect test-seeking behaviour in the blood donor population: making the invisible visible.

BACKGROUND AND OBJECTIVES: Individuals may donate blood in order to determine their infection status after exposure to an increased infection risk. Such test-seeking behaviour decreases transfusion safety. Instances of test seeking are difficult to substantiate as donors are unlikely to admit to such behaviour. However, manifestation in a population of repeat donors may be determined using statistical inference. MATERIALS AND METHODS: Test-seeking donors would be highly motivated to donate following infection risk, influencing the timing of their donation. Donation intervals within 2005-2014 of all Dutch blood donors who acquired syphilis (N = 50), HIV (N = 13), HTLV (N = 4) or HCV (N = 2) were compared to donation intervals of uninfected blood donors (N = 7 327 836) using the Anderson-Darling test. We adjusted for length bias as well as for age, gender and donation type of the infected. Additionally, the power of the proposed method was investigated by simulation. RESULTS: Among the Dutch donors who acquired infection, we found only a non-significant overrepresentation of short donation intervals (P = 0·54). However, we show by simulation that both relatively short and long donation intervals among infected donors can reveal test seeking. The power of the method is >90% if among 69 infected donors >35 (51%) are test seeking, or if among 320 infected donors >90 (30%) are test seeking. CONCLUSION: We show how statistical analysis may be used to reveal the extent of test seeking in repeat blood donor populations. In the Dutch setting, indications for test-seeking behaviour were not statistically significant. This may, however, be due to the low number of infected individuals.

Estimating the risk of dengue transmission from Dutch blood donors travelling to Suriname and the Dutch Caribbean.

BACKGROUND: The risk of dengue transmitted by travellers is known. Methods to estimate the transmission by transfusion (TT) risk from blood donors travelling to risk areas are available, for instance, the European Up-Front Risk Assessment Tool (EUFRAT). This study aimed to validate the estimated risk from travelling donors obtained from EUFRAT. METHODS: Surveillance data on notified dengue cases in Suriname and the Dutch Caribbean islands (Aruba, Curaçao, St. Maarten, Bonaire, St. Eustatius and Saba) in 2001-2011 was used to calculate local incidence rates. Information on travel and donation behaviour of Dutch donors was collected. With the EUFRAT model, the TT risks from Dutch travelling donors were calculated. Model estimates were compared with the number of infections in Dutch travellers found by laboratory tests in the Netherlands. RESULTS: The expected cumulative number of donors becoming infected during travels to Suriname and the Dutch Caribbean from 2001 to 2011 was estimated at 5 (95% CI, 2-11) and 86 (45-179), respectively. The infection risk inferred from the laboratory-based study was 19 (9-61) and 28 (14-92). Given the independence of the data sources, these estimates are remarkably close. The model estimated that 0·02 (0·001-0·06) and 0·40 (0·01-1·4) recipients would have been infected by these travelling donors. CONCLUSIONS: The EUFRAT model provided an estimate close to actual observed number of dengue infections. The dengue TT risk among Dutch travelling donors can be estimated using basic transmission, travel and donation information. The TT risk from Dutch donors travelling to Suriname and the Dutch Caribbean is small.

Surface antigen-negative hepatitis B virus infection in Dutch blood donors.

Hepatitis B virus (HBV) surface antigen (HBsAg) is a reliable marker for HBV infection, but HBsAg-negative forms of HBV infection occur. The introduction of HBV DNA screening of Dutch blood donors, which were not preselected for absence of HBV core antibodies, enabled the characterization of HBsAg-negative HBV infection in healthy persons and a comparison of the HBV genomes involved. The screening of 4.4 million Dutch blood donations identified 23 HBsAg-negative, HBV DNA-positive persons. Serological testing of the index donations, follow-up samples and archived earlier samples was performed to determine the nature of each HBV DNA-only case. Despite low viral loads HBV DNA could be sequenced in 14 out of 23 donors, allowing HBV genotyping and the analysis of mutations in the HBV surface gene. Four types of HBsAg-negative HBV infection were detected: infection in the early stage before occurrence of HBsAg; suppressed infection after vaccination; HBV genotype G infection with decreased HBsAg production; and chronic occult (HBsAg negative) HBV infection. In the donors with occult HBV genotype D infection the HBV surface gene showed multiple "escape" mutations in the HBsAg a-determinant and CTL epitopes, while in an occult genotype A case the surface gene showed no mutations. HBsAg-negative forms of HBV infection in healthy blood donors explain the ongoing transmission of HBV via blood transfusion, if donor screening is limited to HBsAg. The screening of blood donors for HBV DNA and HBV core antibodies seems to cover all stages and variants of HBV infection.

The yield of temporary exclusion of blood donors, exposed to emerging infections abroad.

BACKGROUND AND OBJECTIVES: Emerging infections abroad pose a threat to the safety of blood, donated by travelling blood donors. In this study, the yield of donor deferral after travelling was evaluated, by comparing the estimated numbers of infected donors returning from various affected areas. METHODS: A deterministic model was applied to calculate the number of infected donors, returning from six areas affected by outbreaks: Greece - Macedonia (West Nile fever), Italy - Emilia Romagna (West Nile fever), Thailand (chikungunya), Latvia (hepatitis A), central Turkey (Sicilian sandfly fever) and Italy - Tuscany (Toscana sandfly fever). RESULTS: The estimated number of infections among returning blood donors was surprisingly low, ranging from 0·32 West Nile virus-infected donors per year returning from Macedonia (Greece) to approximately 0·005 infected donors per year returning respectively from Tuscany (sandfly fever), Latvia (hepatitis A) and central Turkey (sandfly fever). CONCLUSION: The yield of the temporary exclusion of blood donors travelling to a specific, affected area is low, but the continuous monitoring of emerging infections and the timely assessment of new threats are laborious and imperfect. Safety measures may be instituted after the greatest threat of a new outbreak has passed. A general deferral of travelling donors may be more appropriate than targeted measures. It can be argued that all donors who stayed outside their country or continent of residency should be deferred for 4 weeks.

Infectivity of pre-seroconversion donations: an analysis of lookback exercises in The Netherlands, 2000-2006.

BACKGROUND AND OBJECTIVES: Blood can be infectious if it is donated shortly before infection with hepatitis B virus (HBV), hepatitis C virus (HCV) or human immunodeficiency virus (HIV) becomes detectable. Lookback exercises may detect infection in recipients of pre-seroconversion donations. This study provides an analysis of the Dutch lookback exercises in the years 2000 through 2006. MATERIALS AND METHODS: All lookback procedures, triggered by 50 repeat donors seroconverting for HBV (n=32), HCV (n=3), HIV (n=14) and HBV + HIV (n=1), were analysed. Recipients and archived samples of the 96 implicated donations were tested. RESULTS: For 76 donations, a stored sample was available for HBV, HCV, or HIV PCR testing, revealing two HBV-DNA-positive pre-seroconversion donations. Ninety-three lookback procedures were initiated, to which 91 of 93 hospitals responded. In 87 of 91 cases, the implicated blood product had been administered. In 39 of 87 cases, the recipient was tested, revealing one HIV and two HBV infections. The HIV infection was considered pre-existent. The two HBV-positive patients received components from the donation of which the repository sample tested positive for HBV-DNA. Components of the second HBV-positive pre-seroconversion donation had not been administered. CONCLUSION: Among 39 recipients of pre-seroconversion donations, 2 (5%) were found HBV infected by transfusion. The labour-intensive lookback procedures did not reveal any conclusive transmissions additional to the infections detected by PCR testing of repository pre-seroconversion samples.