How accurate is serologic testing of plasma pools for hepatitis B virus surface antigen, anti-human immunodeficiency virus 1 and 2, and anti-hepatitis C virus?

Abstract

Objective: The European pharmacopeia prescribes that, during the manufacture of blood derivates, the first homogeneous pool of plasma (for example, after removal of cryoprecipitate) must be tested for hepatitis B virus surface antigen (HBsAg), for hepatitis C virus (HCV) antibodies and for human immunodeficiency virus (HIV) antibodies using test methods of suitable sensitivity and specificity, in order to reduce the residual risk of infection originating from blood products. The present study was performed to verify if commercially available immunoassays, which are licensed for the screening of single serum and plasma samples, are suitable for the determination of HBsAg, anti-HCV, and anti-HIV in plasma pools.

Design: Plasma tools originating from different countries were spiked with HBsAg- and anti-HCV-positive standards (National Institut für Biological Standards, Hertfordshire, UK) and anti-HIV-positive serum. For the determination of HBsAg with and without immune complex dissociation (ICD), anti-HCV and anti-HIV antibodies the Abbott (Delkenheim, Germany) IMx system was used.

Results: In contrast to the testing for anti-HIV and anti-HCV, the detection of HBsAg (0.125 IU/ml detection limit) was influenced by the presence of anti-HBs in plasma pools. Statistically significant differences could be observed between anti-HBs-positive plasma pools and anti-HBs-negative serum samples spiked with HBsAg. The kinetics of HBsAg-anti-HBs complex formation showed that in a plasma pool with a high anti-HBs (329.4 IU/ml) concentration HBsAg was not detectable after 5 h of incubation. After ICD, HBsAg was still detectable in the pool with high anti-HBs content. Anti-HIV antibodies could be detected up to a dilution of 1/480,000, anti-HCV up to a dilution of 1/80, both in a spiked negative serum. Overall, the divergences between spiked plasma and serum were relatively low for anti-HCV and anti-HIV detection.

Conclusion: The Abbott IMx assay permits a highly sensitive detection of HBsAg (after ICD or immediately after thawing of anti-HBs-positive plasma pools), anti-HCV, and anti-HIV in plasma pools. However, in case of a contamination with donations originating from individuals with acute HBV, HIV, or HCV infection or with a poor humoral immune response, serologic testing for HBsAg, anti-HIV, and anti-HCV may fail to detect potentially infectious plasma pools.