New autoantibody analysis may improve early connective tissue disease diagnoses
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A novel, fully automated multiparametric autoantibody analysis may improve the early diagnosis of connective tissue diseases, particularly lupus and Sjögren’s syndrome, according to data published in Arthritis Research & Therapy.
“The need for testing a growing number of antibody specificities requires the use of multiplexing immunoassays,” Nicola Bizzaro, MD, of San Antonio Hospital, in Tolmezzo, Italy, and colleagues wrote. “... Recently, a full automated digital system using particle-based multi-analyte technology (PMAT) has been developed. In this multiplexed assay, each different autoantigen is linked to a unique particle. After incubation of the patient sample, antibody binding is revealed by a camera-based system, thus allowing the simultaneous detection of multiple autoantibody specificity.
“Preliminary results suggest that this novel method may be employed for the simultaneous detection of multiple autoantibodies, improving both diagnostic power and risk stratification in patients according to antibody positivity,” they added. “However, to date, no study analyzed the performance of PMAT in detecting multiple antibodies in CTD.”
To examine the use of multiparametric autoantibody analysis, as performed by the PMAT system, in patients with connective tissue diseases, Bizarro and colleagues collected serum samples 1,247 patients across 13 Italian rheumatology practices. Among the 787 included patients with connective tissue diseases were 166 with systemic lupus erythematosus, 133 with systemic sclerosis, 279 with Sjögren’s syndrome, 106 with idiopathic inflammatory myopathies and 103 with undifferentiated CTDs.
In addition, 339 patients with non-CTD diseases were included — 118 with infectious diseases, 110 with organ-specific autoimmune diseases and 111 with other rheumatic diseases — as were 121 healthy controls.
The researchers recorded specific disease information and demographic data for every included patient. Samples were collected and tested using three distinct panels. The panels were CTD IgG Essential, CTD IgG Comprehensive and Autoimmune Myopathy IgG. In all, the panels investigated the presence of 29 distinct antibodies. Bizzaro and colleagues tested the samples using Aptiva (Inova Diagnostics), a PMAT technology. After the analysis, results were captured using a digital, high-resolution charged coupled device sensor.
According to the researchers, the multiparametric logistic regression revealed that enlarged antibody profiles demonstrate more diagnostic efficacy than individual antibodies or antibodies that make up the classification criteria for a specific disease. Additionally, disease probability increases if there are more present autoantibodies.
“This is the first study that has measured so many autoantibodies in CTD outside the research field by a novel technology now available to clinical laboratories,” Bizzaro and colleagues wrote. “We found that the CTD Essential panel was adequate to diagnose SLE and [primary Sjögren’s syndrome]. The combination of the panel CTD Essential plus CTD Comprehensive yields the best results for SSc diagnosis, and the Autoimmune Myositis panel complemented by Ro52 was the optimal antibody profile to diagnose IIM.
“However, since in the early phase of CTD, identifying a specific disease is not easy, a profile extended to three panels can be an acceptable and advantageous solution. Moreover, it should be noted that none of the 29 autoantibodies tested in this profile could be detected in 14.3% of the patients in this series. Other very specific antibodies can therefore possibly be added in the future to fill the residual diagnostic gap.”
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