The relationship between antinuclear antibody data and antibodies against extractable nuclear antigens in a large...

Anti-extractable nuclear antigen antibodies (anti-ENA) have diagnostic significance in systemic rheumatic disease (SRD).

Anti-ENA were tested in 1685/30,196 sera that were submitted sequentially for antinuclear antibody (ANA) testing. Frequency was stratified by ANA titer and pattern, by referral source, by submitted diagnosis and by patient age and sex.

Anti-ENA frequency increased with ANA titer (7.3% at < 32%-43.3% at ≥ 1024). Anti-histone (11.6%) and anti-SSA/SSB (13.9%) were the most frequent finding with a homo\xadgeneous pattern; anti-SSA/SSB (39.7%) and anti-RNP/anti-Sm (37.7%) were the most frequent finding with a speckled pattern. Sera with speckled, multiple and homogenous ANA patterns accounted for 92.6% of positive anti-ENA findings. At ANA titer ≥ 256, 29.2% of these sera were tested for anti-ENA, of which 41.2% were positive; frequency was higher with an accompanying diagnosis of SRD (53.5% vs. 36.5%, p < 0.004 by χ2-test) but not with referral by rheumatologists (43.5% vs. 35.9%) and did not differ by patient age or sex.

Reflexive anti-ENA testing may be helpful among sera with ANA titer ≥ 256 and homogeneous, speckled or multiple patterns, irrespective of referral source or accompanying diagnosis. Further work is needed to evaluate the clinical impact of this protocol.