[False-positive hepatitis serology after administration of immunoglobulins]

A 17-year-old boy with chronic myelogenous leukemia received a bone marrow transplantation (BMT) from an unrelated donor. 22 days before BMT he had been HBs antigen and anti-HBc negative. 68 days after BMT he was tested again and showed a "seroconversion" for hepatitis B (anti-HBc positive, anti-HBs 59 IU/l), raising the suspicion of a posttransfusion hepatitis. The patient had not received any blood transfusion in the 6 months before BMT. From day 0 to day + 68 he received four red blood cell concentrates and 18 platelet concentrates. The bone marrow donor had been HBs ag and anti-HBc negative.

A stored serum sample of the recipient obtained on day -8 was available and proved to be negative for HBsAg and Anti-HBc IgM, but positive for anti-HBc and anti-HBs. A serum sample from day -22 was negative for all these parameters.

These results can be explained by the administration of 17.5 g of a polyvalent immunoglobulin (Ig) concentrate for CMV prophylaxis on day -9: anti-HBc and anti-HBs (1814 IU/l) were found in the lot that the patient had received. Nine further doses of immunoglobulin concentrates were given up to day + 68.

Four months after the last administration of Ig concentrates, the patient was negative for HBs ag, anti-HBc and anti-HBs.

Ig concentrates contain not only those antibodies, which are given to a patient for treatment, but also all other antibodies contained in the donor plasma pool. Thus administration of Ig concentrates can cause a "false-positive" hepatitis B serology by passive transfer of these antibodies. Such an artificial seroconversion may also lead to a false suspicion of a transfusion transmitted hepatitis B infection.