Problems in ANA test interpretation: a comparison of two substrates.

Comparison of serum antinuclear antibody (ANA) test results on commercial HEp-2 cell culture preparations and fixed mouse kidney sections demonstrated significant differences in end-point titers and pattern production. When manufacturer's suggested screening titers are used, there is also a significant difference in qualitative results and correlation with clinical status. With individual intralaboratory establishment of screening titer levels, some of these differences become less significant, although this study suggests that mouse kidney substrate slides are more sensitive in detecting nonspecific ANA, and that HEp-2 substrate slides are more specific in detecting ANA from cases of systemic lupus erythematosus. Antinuclear antibody substrate selection must be based on classic sensitivity-specificity considerations and the clinical correlation performance desired. Comparisons of interlaboratory or follow-up ANA results are invalid without consideration of substrate variations. Regardless of substrate utilized, each laboratory should establish its own individual screening titers in relation to suitable age groupings.