Christine Bundell¹,  Anna Brusch¹, Gabrielle Rule¹, Sumeya Abdirahman² and Talia James^1
1PathWest Laboratory Medicine
² School of Biomedical Science, University of Western Australia

BACKGROUND: Glutamic acid decarboxylase antibodies (GADAb), seen in type I diabetes mellitus (T1DM), are also associated with neurological conditions, including Stiff Person Syndrome and cerebellar ataxia.  GADAb levels in the serum of neurological patients are significantly higher than levels seen in T1DM patients. The presence of GADAb in CSF may suggest intrathecal antibody production.  GADAb can be visualised by indirect immunofluorescence (IIF) with characteristic granular layer staining on primate cerebellum tissue.  At PathWest GADAbs are routinely measured in serum, however, some assays are only validated for TIDM.  GADAb requests on CSF samples are tested by IIF.   

METHOD: This study is a local audit of CSF samples tested by IIF on a cerebellum substrate and serum GADAb by ELISA and immunoblot, to review the correlation between CSF IIF and serum GADAb levels.  Serum samples were collected within three months of the CSF sample. 

RESULTS: 28 CSF samples were reviewed. 85% of samples were negative by IIF.  Of the remaining four samples, three had an IIF pattern consistent with GADAb, and high titre serum GADAb by ELISA, with detection by immunoblot.

DISCUSSION: This audit demonstrates that a testing algorithm that includes CSF GADAb testing, by IIF aids in identifying intrathecal GADAb. 

The work described in this abstract is a collective contribution from all the listed authors summarising a quality improvement audit for the laboratory.

 AI was not used to prepare this abstract.