Best practice recommendations for laboratory analysis and reporting of cerebrospinal fluid oligoclonal banding and associated tests for multiple sclerosis (MS): a consensus report from the harmonized CSF analysis for MS investigation (hCAMI) subcommittee of the Canadian society of clinical chemists (CSCC).

Cerebrospinal fluid (CSF) oligoclonal banding (OCB) analysis is an important component in the diagnosis of multiple sclerosis (MS). In the 2024 McDonald Criteria for MS diagnosis, CSF-specific OCB can support MS diagnosis, including in those with relapsing or progressive presentations, as well as radiologically isolated syndrome and other non-specific presentations. Despite its clinical importance, laboratory guidelines for analysis and reporting of CSF OCB testing are largely lacking. To address this gap, the Harmonized CSF Analysis for MS Investigation (hCAMI) Subcommittee of the Canadian Society of Clinical Chemists (CSCC) was established to develop evidence-based best practice recommendations for CSF OCB and associated tests and indices. The hCAMI subcommittee is comprised of clinical chemists representing all Canadian laboratories performing CSF OCB testing, and neurologists and a neuroimmunologist from across Canada. Six key areas were identified for harmonization: quality assurance, specimen pairing and timing, reporting of CSF-specific bands, interpreting mirror patterns, band intensity mismatch, reported panel components, and reference intervals/decision limits. Recommendations were informed by national surveys on laboratory practices and clinician preferences, a comprehensive literature review, and original studies addressing evidence gaps. A modified Delphi process, conducted over three iterations, was used to refine and attempt to achieve consensus on 25 draft statements. Of these, 24 achieved consensus (≥80% agreement) and form the final set of hCAMI recommendations. These best practice recommendations aim to promote consistency, accuracy, and clinical utility of CSF OCB testing for MS diagnosis in Canada. While implementation will depend on local resources and workflows, alternative approaches are discussed where appropriate. This initiative establishes a foundation for national harmonization of CSF OCB analysis and supports future integration of best laboratory practices into clinical guidelines.