[Beware of immunoglobulin's passive transfer when interpreting serological analyses!]

Due to their extended indications, intravenous immunoglobulins (IVIg) are increasingly used in hospital setting. After injection, classical IVIg half-life reaches more than 3weeks. IVIg result from the pooling of many blood donations and contain all natural antibodies usually found in the general population. Administered antibodies are known to interfere with many diagnostic assays, particularly those used for infectious serology. It is not recommended to perform serological determination after IVIg infusion. It is recommended to keep a delay of at least 4months after IVIg infusion before doing any serological assay; failure to do so will result in misinterpretation of biological findings. Interpretation of any serological test after IVIg administration should be particularly cautious.