Hepatitis B surface antigen escape mutant in a first time blood donor potentially missed by a routine screening assay.

Mutant forms of hepatitis B surface antigen have developed from a matter of academic interest into a real threat due to the fact that they may remain undetected by certain commercial immunoassays. The risk is especially high when hepatitis B surface antigen is the only strategy to detect an asymptomatic HBV carrier in blood donor screening. Surface antigen escape mutants arise in individuals under medically or naturally induced selective immune pressure and certain mutations are known to be stable and horizontally transmittable. Currently, only one case report has been published from a blood donor carrying an escape mutant. We herewith present a further case of a blood donor with a mutation so far undescribed that alters the common 'a' determinant of HBsAg in such a way that several immunoassays fail to detect this hepatitis B virus infected patient. We conclude that it is absolutely necessary to use HBsAg assays with a high sensitivity for mutant forms in blood donor screening.