Clinical comparison of cultured human epithelial cells and rat liver as substrates for the fluorescent antinuclear antibody test.

Fluorescent antinuclear antibody (ANA) testing was performed on 141 sera from 114 patients with well defined rheumatic diseases including fibrositis syndrome and 24 sera from 24 healthy subjects using HEp-2 cells and rat liver as substrates. ANA titers were almost always higher on HEp-2, in most cases by 1:5 dilutions. ANA positivity or negativity was usually substrate independent, but there were exceptions. Two patients with SLE were ANA positive on HEp-2 only and rat liver only, respectively; patterns were homogeneous. Thirteen of 15 CREST patients had anticentromere antibodies, detected on HEp-2 only. "False-positive" ANA were invariably low titer, speckled and confined to one substrate.