Development of a Certified Reference Material for myeloperoxidase-anti-neutrophil cytoplasmic autoantibodies (MPO-ANCA).

A serum Certified Reference Material (CRM) for supporting reliable autoimmune diagnostics was recently released by the Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre of the European Commission. It was produced in collaboration with a Working Group on the Harmonisation of Autoimmune Tests of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC WG-HAT). This material is aimed at facilitating the standardisation of measurements of anti-myeloperoxidase immunoglobulin G antibodies. The CRM could be used as a common calibrant by clinicians and manufacturers thereby significantly improving the comparability of results from commercial immunoassays used for IgG anti-MPO measurements. This paper provides information on the new CRM and its intended use

Standardization of autoimmune testing - is it feasible?

Correct measurement of autoantibodies is essential for the diagnosis of autoimmune diseases. However, due to the variability of autoantibody results and the heterogeneity of testing, wrong diagnosis is a reality. For this and more reasons, harmonization of testing is of the outmost importance. In this review we have summarized the factors contributing to this variability. The ways with which the working group on harmonization of autoantibody testing of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has been trying to tackle the issue with the production and correct use of certified reference materials (CRMs), is discussed. Finally the advantages and the limitations of the use of CRMs are presented

The certification of anti-myeloperoxidase immunoglobulin G in human serum ERM® - DA476/IFCC

This report describes the production and certification of ERM-DA476/IFCC, a new serum protein reference material intended for the standardisation of measurements of anti-myeloperoxidase immunoglobulin G (anti-MPO IgG) antibodies. The material was produced according to ISO Guide 34:2009. The raw material used to prepare ERM-DA476/IFCC was a plasmapheresis material containing a high concentration of anti-MPO IgG. After a thorough commutability study lyophilised serum was selected as the format for the candidate reference material. Serum processing was performed based on the procedure used for the reference material ERM-DA470k/IFCC. The plasma was converted into serum which was then delipidated. After the addition of preservatives the processed serum was diluted with plasmapheresis solution containing albumin, prior to the transfer of 1 mL aliquots to glass vials. The serum was then lyophilised and the vials closed with rubber stoppers and screw caps under nitrogen atmosphere prior to storage at -70 °C. The between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The material was characterised by an inter-laboratory comparison exercise performed by laboratories of demonstrated competence and with adherence to ISO/IEC 17025 , using a purified anti-MPO IgG preparation as calibrant. This was achieved using a value transfer protocol previously used in the characterisation of ERM-DA470k/IFCC. Technically invalid results were removed. However no other outliers were eliminated on statistical grounds only. Uncertainties of the certified values were calculated in accordance to the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties relating to possible lack of homogeneity, instability and characterisation. The material is intended for the calibration of methods and quality control. As any reference material, it can also be used for control charts or validation studies. The CRM is available in glass vials containing the lyophilised residue of 1 g serum. The minimum amount of reconstituted sample to be used is 10 μL. The CRM was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium

Certified reference material against PR3 ANCA IgG autoantibodies. From development to certification.

Background The importance of the standardisation of immunoassays for autoantibodies has been widely discussed. The appropriate use of certified reference materials (CRM) could contribute to a more accurate diagnosis and follow-up of a series of diseases such as small vessel-associated vasculitis. This is a systemic autoimmune disorder during which two autoantibodies can be present, MPO ANCA IgG and PR3 ANCA IgG. Results from different commercially available immunoassays used for PR3 ANCA IgG measurement can vary significantly. Therefore the potential for improvement using a suitable certified reference material was assessed and led to the development of a CRM. Methods Thirty clinical samples were evaluated using 10 immunoassays. The correlation between results from these assays was assessed in a pairwise manner. Feasibility studies were conducted in order to find a reference material format most suitable for the preparation of a CRM. Results The evaluation of two sets of 30 clinical samples with 10 assays showed that differences between assays can result in different interpretations for individual clinical samples. Most of the samples had the same result classification in all assays. However, six of the samples tested led to inconsistent results. Conclusions The correlation between results from clinical samples was systematically good for combinations of eight of those assays. Therefore, it should be possible to improve the comparability of results using a commutable CRM for calibration. Based on these studies, a final format for the CRM was selected and eventually produced and certified for its PR3 ANCA IgG content