Potential Confounding of Diagnosis of Rabies in Patients with Recent Receipt of Intravenous Immune Globulin

Abstract

© 2018, Department of Health and Human Services. All rights reserved. What is already known about this topic? The presence of a high concentration of serum Rabies lyssavirus neutralizing antibodies (RLNAs) in a patient with an illness compatible with rabies and no history of rabies vaccination is considered diagnostic for human rabies. This case definition does not take into account whether the patient has recently received intravenous immune globulin (IVIG). What is added by this report? This report describes six patients who met the case definition for human rabies because they had illnesses compatible with rabies, had not been vaccinated against rabies, and were found to have a high concentration of serum RLNAs. However, none of these patients received a rabies diagnosis; rather, they were considered to have been passively immunized for rabies through receipt of IVIG. What are the implications for public health practice? Positive RLNA test results should be interpreted with caution in a patient who has not been vaccinated against rabies but who has recently received IVIG. If RLNAs are detected in serum collected after IVIG administration, additional testing of IVIG from the lot or lots used to treat the patient can be helpful in evaluating the likelihood of rabies.