title: Transient spurious intrathecal immunoglobulin synthesis in neurological patients after therapeutic apheresis.
abstract: BACKGROUND
  The analysis of cerebrospinal fluid (CSF) is usually done under steady-state conditions, when proteins (e.g., immunoglobulins) reach diffusion equilibrium between blood and CSF. However, little data has been published on CSF analysis under non-steady-state conditions after therapeutic apheresis. By reducing serum proteins (e.g., immunoglobulins), while leaving CSF unchanged, therapeutic apheresis might cause spuriously altered intrathecal immunoglobulin fractions.
  
  
  METHODS
  Based on the incidental finding of plasma exchange-induced increased intrathecal immunoglobulin fractions in a cohort of 12 unsystematically selected patients with various neurological disorders, we retrospectively investigated CSF results that had been raised during routine diagnostic work-up from 41 consecutive neurological patients (predominantly Guillain-Barré syndrome and autoimmune encephalitis) treated with plasmapheresis or immunoadsorption in a tertiary care university hospital in whom lumbar puncture (LP) was performed after a varying number of treatments of therapeutic apheresis.
  
  
  RESULTS
  Only when LP was performed 1 day after therapeutic apheresis, spurious quantitative intrathecal immunoglobulin (Ig) synthesis of at least one subclass (IgG, IgA and/or IgM) was found in 68.4 % of the patients, irrespective of the number of treatments, in all age groups and independent of other previous immunotherapies (e.g., steroids). This phenomenon occurred only transiently and was almost always accompanied by an elevation of the IgG index. In one patient, an elevated IgG index was noticed even 2 days after plasmapheresis. Neither quantitative Ig synthesis, nor elevated IgG index was observed when the LP was performed three or more days after therapeutic apheresis.
  
  
  CONCLUSIONS
  Spurious quantitative intrathecal Ig synthesis and increased IgG index are common findings shortly after plasmapheresis or immunoadsorption due to altered serum immunoglobulin levels. Knowledge of this phenomenon is needed for clinicians to prevent false interpretations leading to unnecessary diagnostic and therapeutic procedures. Misdiagnoses can be avoided by considering the characteristic CSF constellation including absence of oligoclonal bands and the close temporal relation to therapeutic apheresis.
authors.affiliation: Department of Neurology and Neurophysiology, University Hospital Freiburg, Breisacher Strasse 64, D-79106, Freiburg, Germany. benjamin.berger@uniklinik-freiburg.de.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Berger
authors.affiliation: Department of Neurology and Neurophysiology, University Hospital Freiburg, Breisacher Strasse 64, D-79106, Freiburg, Germany. tilman.hottenrott@uniklinik-freiburg.de.
authors.forename: Tilman
authors.initials: T
authors.lastname: Hottenrott
authors.affiliation: Department of Neurology and Experimental Neurology, Charité University Medicine Berlin, Charitéplatz 1, D-10117, Berlin, Germany. jonas.leubner@charite.de.
authors.forename: Jonas
authors.initials: J
authors.lastname: Leubner
authors.affiliation: Department of Neurology and Neurophysiology, University Hospital Freiburg, Breisacher Strasse 64, D-79106, Freiburg, Germany. rick.dersch@uniklinik-freiburg.de.
authors.forename: Rick
authors.initials: R
authors.lastname: Dersch
authors.affiliation: Department of Neurology and Neurophysiology, University Hospital Freiburg, Breisacher Strasse 64, D-79106, Freiburg, Germany. sebastian.rauer@uniklinik-freiburg.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Rauer
authors.affiliation: Department of Neurology and Neurophysiology, University Hospital Freiburg, Breisacher Strasse 64, D-79106, Freiburg, Germany. oliver.stich@uniklinik-freiburg.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Stich
authors.affiliation: Department of Neurology and Experimental Neurology, Charité University Medicine Berlin, Charitéplatz 1, D-10117, Berlin, Germany. harald.pruess@charite.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Prüss
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001781:Blood Component Removal; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis / Q000097:blood / Q000134:cerebrospinal fluid*; D007163:Immunosorbent Techniques; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000134:cerebrospinal fluid* / Q000628:therapy; D012189:Retrospective Studies; D013129:Spinal Puncture; D055815:Young Adult
chemical_list: D007136:Immunoglobulins
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