False-positive serology following intravenous immunoglobulin and plasma exchange through transfusion of fresh frozen plasma in a patient with pemphigus vulgaris

Challenge of hepatitis B testing following intravenous immunoglobulin therapy in patients with autoimmune skin diseases

Intravenous immunoglobulin (IVIg) contains pooled immunoglobulins from the plasma of healthy blood donors. All plasma samples are tested for HIV, hepatitis viruses (A, B, and C), and parvovirus B19. As part of this screening step, nucleic acid amplification technology (NAT) is used and allows the presence of specific antibodies targeting viral structures that are commonly used to test for infection status, such as anti-hepatitis B surface antigen (HBs) or anti-hepatitis B virus core (HBc) antibodies. For this reason, manufacturers point to the possibility of false-positive viral serological test results following IVIg treatment due to the passive transfer of antibodies. IVIg therapy is commonly used to manage patients with severe, treatment-refractory autoimmune skin diseases. The aim of this cohort study was to retrospectively quantify newly-discovered positive serological HBV test results after IVIg treatment in patients with autoimmune skin diseases. Between March 2018 and June 2021, 28 patients with autoimmune skin diseases received IVIg therapy, of whom 17 were longitudinally followed-up. None of the patients had evidence of active HBV infection prior to IVIg therapy. All patients (n = 17) had detectable anti-HBs antibodies and 12 patients had anti-HBc antibodies 4 weeks after commencing IVIg treatment. Passive antibody transfer seems the most likely interpretation. Nevertheless, complete serological hepatitis assessment should be performed to exclude a new infection. We recommend hepatitis screening before IVIg therapy to prevent diagnostic confusion which may arise due to passive antibody transfer.

Misleading Positive Serology for Cat Scratch Disease Following Administration of Intravenous Immunoglobulin

Cat scratch disease (CSD), caused by Bartonella henselae, usually presents as regional lymphadenopathy/lymphadenitis, known as typical CSD or as atypical CSD, which includes, among others, neurological manifestations. Serology for anti-B. henselae IgG antibodies is the most commonly used diagnostic tests for CSD. Intravenous immunoglobulin (IVIG) is given for an increasing number of medical conditions and may cause interference with serological testing. We report six patients with neurological manifestations and two patients with Kawasaki disease mimicking typical CSD, mistakenly diagnosed as CSD due to false-positive serology following IVIG therapy. Bartonella IgG serology was positive one to six days after IVIG administration and reverted to negative in seven of eight patients or significantly decreased (1 patient) ≤30 days later. In patients with CSD, IgG titers remained essentially unchanged 15–78 days after the positive serum sample. An additional eight patients treated with IVIG for various conditions were evaluated prospectively. All were seronegative one day pre-IVIG infusion, five patients demonstrated an increase in the IgG titers one to three days after IVIG administration, one interpreted as positive and four as intermediate, whereas three patients remained seronegative, suggesting that false seropositivity after IVIG therapy may not occur in all patients. Treatment with IVIG can result in false-positive serology for B. henselae. Increased awareness to the misleading impact of IVIG is warranted to avoid misinterpretation. Repeat testing can distinguish between true and false serology. Preserving serum samples prior to IVIG administration is suggested.