A Model to Estimate Risk of Infection with Human Herpesvirus 8 Associated with Transfusion from Cross‐Sectional Data

Combining assays for estimating prevalence of human herpesvirus 8 infection using multivariate mixture models

For many diseases, it is difficult or impossible to establish a definitive diagnosis because a perfect "gold standard" may not exist or may be too costly to obtain. In this paper, we propose a method to use continuous test results to estimate prevalence of disease in a given population and to estimate the effects of factors that may influence prevalence. Motivated by a study of human herpesvirus 8 among children with sickle-cell anemia in Uganda, where 2 enzyme immunoassays were used to assess infection status, we fit 2-component multivariate mixture models. We model the component densities using parametric densities that include data transformation as well as flexible transformed models. In addition, we model the mixing proportion, the probability of a latent variable corresponding to the true unknown infection status, via a logistic regression to incorporate covariates. This model includes mixtures of multivariate normal densities as a special case and is able to accommodate unusual shapes and skewness in the data. We assess model performance in simulations and present results from applying various parameterizations of the model to the Ugandan study.

Transmission of human herpesvirus 8 by blood transfusion

BACKGROUND

Whether human herpesvirus 8 (HHV-8) is transmissible by blood transfusion remains undetermined. We evaluated the risk of HHV-8 transmission by blood transfusion in Uganda, where HHV-8 is endemic.

METHODS

We enrolled patients in Kampala, Uganda, who had received blood transfusions between December 2000 and October 2001. Pretransfusion and multiple post-transfusion blood specimens from up to nine visits over a 6-month period were tested for HHV-8 antibody. We calculated the excess risk of seroconversion over time among recipients of HHV-8-seropositive blood as compared with recipients of seronegative blood.

RESULTS

Of the 1811 transfusion recipients enrolled, 991 were HHV-8-seronegative before transfusion and completed the requisite follow-up, 43% of whom received HHV-8-seropositive blood and 57% of whom received seronegative blood. HHV-8 seroconversion occurred in 41 of the 991 recipients. The risk of seroconversion was significantly higher among recipients of HHV-8-seropositive blood than among recipients of seronegative blood (excess risk, 2.8%; P<0.05), and the increase in risk was seen mainly among patients in whom seroconversion occurred 3 to 10 weeks after transfusion (excess risk, 2.7%; P=0.005), a result consistent with the transmission of the virus by transfusion. Blood units stored for up to 4 days were more often associated with seroconversion than those stored for more than 4 days (excess risk, 4.2%; P<0.05).

CONCLUSIONS

This study provides strong evidence that HHV-8 is transmitted by blood transfusion. The risk may be diminished as the period of blood storage increases.