Screening Tests for Systemic Lupus Immunology Review 411
Erythematosus (SLE)
TESTS
Fluorescent
antinuclear
antibody
(FANA)
EIA antinuclear
antibody
(EIA-ANA)
COMMENTS
Indirect immunofluorescence (IIF). Sub-
strate is human epithelial tumor cell line
(HEp-2). Detects abs to >100 autoantigens.
Staining patterns reported but not consid-
ered as significant as in past. Labor inten-
sive. Subjective. Still considered gold
standard by rheumatologists.Easier, less expensive. Can be automated.
Interpretation not subjective. Not as many
antigens as IIF.SENSITIVITY
High. 95%–100% of
SLE patients test pos.May not be as
sensitive as IIF.SPECIFICITY
Low. Abs present in other autoimmune
diseases, 2% of healthy individuals, 75%
of elderly. Dilutions tested to eliminate
low titer rxn in normal population. Cutoff
dilution to report pos usually ≥1:80. End-
point titer may be reported. Generally
higher in SLE.Low.