Screening tests for antinuclear antibodies (ANA): selective use of central nuclear antigens as a rational basis for screening by ELISA.

Rational, fully automated ELISA screening tests for ANA have become accessible for routine use. Full length, recombinant or purified naturally expressed antigens can be selected to deliver well defined screening tests, designed to detect ANAs of established clinical significance, while unknown specificities with no clear biological impact are omitted. By comparing results of ANA screening by immunofluorescence (IIF) on tissue section with HEp-2 cells, a correlation of 88% was revealed, while 86% of HEp-2-positive sera bound tissue sections. Eighty-nine percent of HEp-2 ANA-positive sera bound in ANA ELISA I. Seventy-five percent of ANAs detected in ELISA I also bound in ELISA II. These correlations were statistically significant. ANAs detected in ANA ELISA I were all detected upon retesting in both ANA screening ELISA systems, and also by antigen-specific ELISAs. Specific ANAs defined by ELISA, immunodiffusion or Crithidia tests were detected in both ANA ELISA tests. These data demonstrate that most ANAs detected by immunofluorescence tests contain a dominating repertoire of specificities covered by the ANA ELISA systems. The sensitivity of the different ELISA tests can easily be adjusted to internationally defined consensus levels, and screening for ANA using both ELISA systems detects expected ANA specificities in ongoing international quality assessment programs.