Connective tissue

The gold standard for the determination of ANA is the indirect immunofluorescence test (IIFT) with human epithelial cells (HEp-2), which is known for its high sensitivity and specificity. In the microscopic evaluation it is possible to establish precisely how an indicator dye (generally fluorescein) is distributed in the cells. Depending on the location of the individual autoantigens, a typical fluorescence pattern for every type of autoantibody bound will appear.
The revised international consensus on a standardized nomenclature of HEp-2 cell patterns in indirect immunofluorescence (ICAP, www.anapatterns.org) defines 15 nuclear, 9 cytoplasmic and 5 mitotic patterns which are relevant for the diagnostics of various autoimmune diseases.

Furthermore, ICAP recommends IIFT results be confirmed by additional specific antibody tests (e.g. ELISA, line blot, ChLIA). However, the exclusive use of these monospecific test methods is insufficient for the determination of autoantibodies against cell nuclei, as not all relevant antigens are available yet in purified form. Thus, the corresponding ANAs can only be detected by IIFT.