ALGORITHM FOR ANTINUCLEAR ANTIBODIES IN SUBJECTS WITH CLINICAL SUSPICION OF AUTOIMMUNE DISEASE
- Laura Naranjo, Spain
Abstract
Background and Aims
Antinuclear antibodies (ANA) are essential in the diagnosis of systemic autoimmune rheumatic diseases (SARDs) and they could appear years before the clinical onset of the disease. Different assays for ANA screening are available, such as indirect immunofluorescence (IIF) on HEp-2 cells and Multiplex fluorescent immunoassay (MFI). This study aimed to clarify the importance of ANA detected only by IIF in the future development of SARDs and to recommend a laboratory algorithm that integrates the available diagnostic approaches to optimise the diagnosis of ANA IIF+MFI- subjects.
Methods
A total of 9,291 subjects with clinical suspicion of SARDs were evaluated for ANA by IIF and MFI. Only 198 subjects (2.1%) were ANA IIF+MFI- and were followed-up for 2 years. ANA were evaluated using IIF on HEp-2 cells and MFI on the BioPlex 2200.
Results
The ANA IIF+MFI- cohort consisted of 106 subjects with high clinical suspicion of SARDs, 26 subject with other autoimmune diseases (not-SARDs) and 66 subjects with minor symptoms or ANA requested in check-ups. Only 94 subjects underwent re-evaluation and were followed-up for 2 years. Most re-evaluated subjects (51 patients, 54%) became ANA negative by both assays (mainly rheumatoid arthritis, polymyalgia and inflammatory bowel disease patients) and 35 subjects remained ANA IIF+MFI- (37%, principally systemic sclerosis and systemic lupus erythematosus patients). A new algorithm for ANA evaluation was suggested.
Conclusions
According to the proposed algorithm, ANA IIF+MFI- subjects should be screened by an alternative solid-phase assay such as line-immunoassay or ELISA, where appropriate antigens for the diagnosis of SARDs are represented.