Autoantibody detection with indirect immunofluorescence on HEp-2 cells: Starting serum dilutions for systemic rheumatic diseases

► This paper evaluates the clinical and economic impact generated by starting ANA dilution at 1:160. ► A total of 13,233 samples were processed, and only ANA dilutions of 1:160 and higher showed significantly increased positive predictive value for anti-ENA and anti-dsDNA when compared to 1:40 titer. ► The cut-off 1:160 achieved making 17% less ANA tests, 42% less anti-ENA determinations and 36% less anti-dsDNA tests. ► Setting the starting dilution of ANA at 1:160 avoids unnecessary studies, increases ANA positive predictive values for anti-ENA and anti-dsDNA, and generates clinical and economic benefits.