Relevance of the immunofluorescence pattern for interpretation of the ana test - The case of the dense fine speckled pattern

Abstract

Determination of autoantibodies against cellular antigens (ANA-HEp-2) has undergone several methodological changes over the decades and for an appropriate evaluation of results requires reflection on its sensitivity and specificity properties. Currently the test is known to have high sensitivity and questionable specificity since it is frequently positive in a considerable number of non-autoimmune subjects. Awareness that a substantial portion of the population has a positive ANA-HEp-2 test demands that characteristics permitting to distinguish positive tests in autoimmune patients from positive tests in non-autoimmune subjects be identified. Among these characteristics are noteworthy the titer and the fluorescence pattern. In particular, one must bear in mind that the fluorescence pattern results from recognition by autoantibodies of distinct cellular structures and, therefore, the fluorescence pattern provides a preliminary indication of possible autoantigens targeted by the sera being tested. An emblematic example is the nuclear dense fine speckled pattern. It was originally studied by Ochs and collaborators in 1994 in a restricted number of patients with interstitial cystitis. Further studies demonstrated its frequent occurrence in laboratory practice in individuals with diverse non-autoimmune clinical conditions. Indeed, this pattern is one of the most frequently observed in non-autoimmune patients with an ANA-HEp-2 positive reaction. The present review intends to provide elements allowing the clinician to perform a critical interpretation of results of an ANA-HE-2 test, including analysis of the titer and the fluorescence pattern.