Search

Objectives Diagnosis of type I hypersensitivity is based on anamnesis, provocation as well as blood- and skin testing. Multiplex specific IgE (sIgE) testing enables determination of sIgE antibodies against multiple recombinant or purified natural allergen components. The aim of this study was to evaluate the performance of the novel ALEX2® (Allergy Explorer, ALEX2 test introduced on the market November 2019) multiplex platform and to compare it with the ImmunoCAP ISAC® test system. Methods Serum samples of 49 patients, routinely determined with ISAC, were selected based on positive results covering in total most of the 112 ISAC components. Cohen’s kappa, negative percent agreement (NPA), and positive percent agreement (PPA) of ALEX2 data compared to ISAC data (as a non-reference standard) were computed for those allergen components present on both platforms (n=103). Furthermore, in some samples sIgE results against allergen extracts and/or -components tested with either ImmunoCAP® (ThermoFisher) or IMMULITE® (Siemens) were available and compared to ALEX2 results. Results The overall agreement between ISAC and ALEX2 common allergen components was 94%. NPA and PPA were respectively 95 and 90%. Kappa values differed for specific allergen groups and varied between 0.60 and 0.92 showing moderate to almost perfect agreement. Of the qualitative discrepancies between ALEX2 and ISAC, 59% were related to weak positive results i.e. results under 1 kUA/L or 1 ISU, respectively. Conclusions The method comparison between ISAC and ALEX2 multiplex tests showed a high concordance for those allergen components present on both platforms.

Idiopathic inflammatory myopathies (IIM) are a group of diseases characterized by immune-mediated muscular lesions that may be associated with extra-muscular manifestations involving skin, lungs, heart or joints. Four main groups of IIM can be distinguished: dermatomyositis (DM), overlap myositis including mainly anti-synthetase syndrome (ASS), immune mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). Myositis-specific autoantibodies (MSA) are increasingly recognized as valuable tools for diagnosis, classification and prognosis of IIM. For example, ASS is associated with anti-aminoacyl tRNA synthetase antibodies (anti-Jo-1, PL-7, PL-12, …), IMNM with anti-SRP and anti-HMGCR; IBM with anti-cytosolic 5'nucleotidase 1A (cN1A), and DM with anti-Mi-2, anti-MDA-5, anti-TIF-1γ, anti-NXP-2 and anti-SAE. Moreover, anti-MDA-5 is associated with amyopathic myositis and interstitial lung disease and anti-TIF-1γ and anti-NXP-2 with juvenile DM as well as malignancy in patients >40 years. Most MSA have initially been discovered by immunoprecipitation. In routine laboratories, however, MSA are screened for by indirect immunofluorescence and identified by (automated) monospecific immunoassays or by multispecific immunoassays (mainly line/dot immunoassays). Validation of these (multispecific) assays is a challenge as the antibodies are rare and the assays diverse. In this review, we give an overview of the (clinical) performance characteristics of monospecific assays as well as of multispecific assays for detection of MSA. Although most assays are clinically useful, there are differences between techniques and between manufacturers. We discuss that efforts are needed to harmonize and standardize detection of MSA. ispartof: AUTOIMMUNITY REVIEWS vol:18 issue:3 pages:293-305 ispartof: location:Netherlands status: published

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of connective tissue diseases, collectively known as myositis. Diagnosis of IIM is challenging while timely recognition of an IIM is of utter importance considering treatment options and otherwise irreversible (severe) long-term clinical complications. With the EULAR/ACR classification criteria (2017) considerable advancement has been made in the diagnostic workup of IIM. While these criteria take into account clinical parameters as well as presence of one autoantibody, anti-Jo-1, several autoantibodies are associated with IIM and are currently evaluated to be incorporated into classification criteria. As individual antibodies occur at low frequency, the development of line blots allowing multiplex antibody analysis has improved laboratory diagnostics for IIM. The Euroline myositis line-blot assay (Euroimmun) allows screening and semi-quantitative measurement for 15 autoantibodies, i.e. myositis specific antibodies (MSA) to SRP, EJ, OJ, Mi-2α, Mi-2β, TIF1-γ, MDA5, NXP2, SAE1, PL-12, PL-7, Jo-1 and myositis associated antibodies (MAA) to Ku, PM/Scl-75 and PM/Scl-100. To evaluate the clinical significance of detection and levels of these autoantibodies in the Netherlands, a retrospective analysis of all Dutch requests for extended myositis screening within a 1 year period was performed. A total of 187 IIM patients and 632 non-IIM patients were included. We conclude that frequencies of MSA and MAA observed in IIM patients in a routine diagnostic setting are comparable to cohort-based studies. Weak positive antibody levels show less diagnostic accuracy compared to positive antibody levels, except for anti-NXP2. Known associations between antibodies and skin involvement (anti-MDA5, anti-TIF1-γ), lung involvement (anti-Jo-1), and malignancy (anti-TIF1-γ) were confirmed in our IIM study population. The availability of multiplex antibody analyses will facilitate inclusion of additional autoantibodies in clinical myositis guidelines and help to accelerate diagnosing IMM with rare but specific antibodies., Highlights • Similar frequency of MAA and MSA in diagnostic setting compared to cohort studies. • Positive levels of MSA/MAA show better diagnostic accuracy compared to weak positive levels. • Anti-NXP2 differentiates already at weak positive level between IIM and non-IIM patients. • Anti-TIF1-γ is associated with malignancy and anti-MDA5 and TIF1-γ with skin disease. • Anti-Jo-1 is associated with lung disease.