Testing for antinuclear antibodies (ANA) by the indirect immunofluorescence test (IFT) is regarded as a fundamental serological screening method for diagnosing connective tissue diseases (CTD). In the case of a negative result exclusion of certain CTDs is indicated, especially systemic lupus erythematosus, and a positive ANA result is the starting point for further tests aimed at finding disease-specific autoantibodies. The recently discovered antibodies against lens epithelium-derived growth factor (LEDGF/DSF70) deviate from the normal interpretation pattern in ANA diagnostics. These antibodies give rise to a characteristic dense fine speckled (DSF) immunofluorescence pattern in IFT and target the ubiquitously expressed nuclear stress protector protein LEDGFp75. They can be detected, sometimes in high titers, not only in patients with diverse disorders of the skin or eyes and with neoplasms but also in persons with relatively mild or unspecific complaints and even in apparently healthy individuals; however, they are less frequent in CTD. These anti-LEDGF antibodies can be found in all age groups with a tendency to a higher prevalence in younger people and the frequency does not increase in advanced age. The vast majority of anti-LEDGF carriers are female. The CTDs with isolated anti-LEDGF antibodies, i. e. unaccompanied by autoantibodies typical for the respective CTD, are extremely rare. Detection of ANA exclusively with a DSF immunofluorescence pattern and confirmed by a specific anti-LEDGF binding assay, does not therefore indicate the presence of CTD but is indicative of exclusion of systemic lupus erythematosus, systemic sclerosis and an ANA-associated overlap syndrome, similar to a completely negative ANA result.
Keywords: Autoantibodies; Fluorescent antinuclear antibody test; Overlap syndrome; Systemic lupus erythematosus; Systemic sclerosis.