Title:Diffuse fine speckled (DFS70) antibody in ANA testing: identification and proposed management in a New Zealand tertiary hospital setting

Author:PM austin, SM McCarthy, HT Faiva-Thompson.

Abstract:Objectives: DFS70 antibody gives an ANA Immunofluorescent (IIF) staining pattern (homogeneous / speckled), frequently at high titre that is often seen in AARD patients although DFS70 antibody is rarely associated with systemic autoimmune – based rheumatic disease. The purposes of this study were to (a) identify if DFS70 antibody was present in our test population (b) determine if DFS70 patterns could be identified with first-round IIF ANA testing (c) establish the relationships between IIF, CMIA (Chemiluminescence) and LIA (Line Immunoassay) methodologies for identification of DFS70 antibody and (d) propose a testing algorithm for implementation at LabPLUS that would allow the identification of DFS70 antibody. This is the first published study on a NZ patient cohort.
Methods: Patients referred for routine ANA testing were selected as presumptive DFS70 antibody positive and were then subsequently tested by both CMIA (INOVA Diagnostics BIOFLASH™) and LIA (Euroimmun EUROLINE Profile 3 Plus DFS70™) methodologies.
Results: DFS70 antibody was proven to occur in NZ patients referred for ANA testing. IIF methodology in the hands of experienced operators correctly identified approximately 80% of DFS70 antibody positive patients. As second round confirmatory assays, both the CMIA and LIA methodologies were effective in the role.
Conclusions: On the basis of the results of the study a testing algorithm was designed to allow the identification and reporting of DFS70 antibody. It is believed that when testing is implemented there will be significant fiscal benefits from reduced inappropriate testing as well as improved rheumatology outpatient clinic patient triaging over time. We further believe that implementation of DFS70 antibody testing and reporting will, for a proportion of patients reduce
their anxiety and greatly reduce if not completely eliminate the opportunity for inappropriate treatment based on apparently significant ANA results.
Keywords: AARD, IIF, CMIA, LIA, DFS70 antibody, NZ patient cohort, testing algorithm.
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