Standardisation of autoantibody testing

Autoimmune serology testing is moving from qualitative or semi-quantitiative methods to quantitative testing driven by increasing workload, consolidation and de-skilling in laboratories. However, autoantibodies show variation, both between patients, and within a patient at different points in their disease course. There are no ‘reference methods’ and there is variability in every element of the analytical process. Considering these complexities, it is unsurprising that there is enormous variation (up to 1000×) in autoantibody results measured by different methods and this variation generates a significant clinical risk in interpreting and acting on the results. A group led by the IFCC Committee on Harmonisation of Autoantibody Testing has produced certified reference materials for IgG anti-myeloperoxidase (ERM-DA476/IFCC) and IgG anti-proteinase 3 (ERM-DA483/IFCC) with values assigned in mg/L. The use of these materials will significantly reduce the spread of numerical results over different methods and should provide an independent reference point of reference to minimise batch to batch variation and to help identify other elements of the methods needing harmonisation. However, they will not solve all the issues of variability in autoantibody quantification, particularly relating to the behaviour of individual patients’ samples.