Measurement of antinuclear antibodies: Assessment of different test systems

The performance of rat liver and HEp-2 in the detection of antinuclear anti bodies (ANA) was studied by two independent sites and compared against an A NA enzyme immunoassay (EIA) screen and EIA systems for the measurement of a ntibodies to double-stranded DNA (dsDNA) and ENA. Sixty-two sera from patie nts with connective tissue disease (CTD) and 398 from controls suffering fr om other disorders were included, The level of agreement was, for HEp-2 and rat liver (within one site), 82.0% (ANA positive/ANA negative) and 51.0% ( ANA pattern); and for HEp2- and HEp-2 (between sites), 71.8 and 86.5%. On s era with the ANA homogeneous pattern, the measurement of anti-ENA EIA added little to the detection rate with anti-dsDNA EIA alone. On ANA speckled se ra, the EIA reactivity depended on the reaction of the mitotic cells: while sera with positive mitoses reacted similarly to ANA homogeneous sera, in t hose with negative mitoses the measurement of anti-ENA added about 10% to t he detection rate achieved with anti-dsDNA alone. The measurement of anti-S cl-70 and anti-Jo-1 did not markedly improve the positive rate with classic al ENA (anti-SSA, -SSB, -Sm, and -RNP) alone, raising doubts about the cost efficiency of including these measurements in unselected sera, The AVA EIA dentified patients with CTD at a rate similar to that for rat liver and HE p-2, However, up to 98% of the sera found to be negative by ANA EIA but pos itive by use of rat liver and HEp-2 were from controls. Thus, the ANA EIA m ay possible be used as an alternative screen, particularly in laboratories with a high frequency of sera from patients not suffering from CTD.