This article is more than 5 years old. Information may no longer be current.
Study: Disease activity can be measured using FIDIS assay in patients with SLE
An analysis of four antibody assays showed FIDIS and CLIFT demonstrated the highest concordance for disease detections, and that FIDIS can also be used to monitor disease activity in patients with systemic lupus erythematosus.
Researchers studied data from 178 patients with systemic lupus erythematosus (SLE) enrolled in a regional Swedish SLE register between 2008 and 2011. All patients with SLE fulfilled the 1982 American College of Rheumatology and/or the 2012 Systemic Lupus International Collaborating Clinics (SLICC-12). Mean disease duration was 11 years.
Ninety percent of the patients were women and 90% were white, with a mean age 50 years. Fifty-four patients with primary Sjögren syndrome (pSS) and 95 patients with rheumatoid arthritis (RA) were recruited as control participants.
Disease activity was recorded at each follow-up visit using the SLE Disease Activity Index 2000 (SLEDAI-2K), and serum samples were analyzed for immunoglobulin G (IgG) anti-dsDNA by bead-based multiplex assay (FIDIS; Theradig), fluoroenzyme-immunoassay (EliA; Phadia/Thermo Fisher Scientific), Crithidia luciliae immunofluorescence test (CLIFT; ImmunoConcepts) and line blot (EUROLINE; Euroimmun). Additionally, disease identification specificity and sensitivity were calculated for each method according to manufacturer guidelines.
CLIFT showed the highest (98%) disease specificity for SLE, but the lowest (24%) for identifying anti-dsDNA-positive patients, according to the researchers. EliA was most specific (35%) for identifying anti-dsDNA-positive patients.
The researchers found FIDIS was the least specific for identifying SLE, but it did not identify any patients without SLE, unlike EliA and EUROLINE.
When the manufacturer’s reference cutoff for EUROLINE, FIDIS, and EliA was doubled according to recommendations in the SLICC-12 criteria for the use of ELISA, high specificity for all methods (98 to 99%) was shown, but sensitivity was reduced using CLIFT.
Correlations and concordances between methods were evaluated in the 178 cross-sectional SLE sera. Samples below the cutoff were assigned a value of 0 to avoid influence of level differences among double-negative samples in the correlation analyses.
All methods correlated significantly and showed concordance of 72% or greater. The strongest correlation and concordance at manufacturers’ cutoff limits was found between CLIFT and FIDIS, according to the researchers.
The overlap between assay methods in the disease control groups was 32% for pSS and 11% for RA, with the highest overlap between CLIFT and FIDIS. Anti-dsDNA–positive patients with pSS did not differ significantly from anti-dsDNA–negative patients with pSS in the presence of one or more extraglandular manifestations using any method.
For diagnostic purposes, the researchers concluded that CLIFT and FIDIS were the most accurate methods, and that findings showed FIDIS could be used to effectively monitor disease activity. – by Shirley Pulawski
Disclosures: The researchers report no relevant financial disclosures.