Abnormal antinuclear antibody titers are less common than generally assumed in established cases of systemic lupus erythematosus.
OBJECTIVE
To evaluate antinuclear antibody (ANA) tests in established cases of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) by indirect immunofluorescence microscopy (F-ANA) and enzyme-immunoassays detecting antinucleosomal antibodies (ANSA-EIA).


METHODS
Sera from 50 patients with SLE and 65 patients with RA were analyzed regarding abnormal concentrations of F-ANA (serum dilution>or=1:200=95th percentile among 300 healthy blood donors). The sera were also analyzed with 2 commercial ANSA-EIA kits.


RESULTS
An abnormal F-ANA titer occurred in 76% of the SLE sera compared to 23% in RA, and was not related to present use of antirheumatic drugs. At dilution 1:50, 84% of the SLE sera were F-ANA-positive compared to 20% of healthy women. Forty percent and 56%, respectively, of the SLE sera tested positive in the 2 ANSA-EIA kits. By the most sensitive assay, 96% of the ANSA-positive SLE sera produced a homogenous (chromosomal) F-ANA staining pattern compared to 18% of the ANSA-negative SLE sera. Ten of the 15 F-ANA-positive RA sera (63%) generated homogenous F-ANA staining and 13 (20%) tested positive in the most sensitive ANSA-EIA, but with no correlation to the F-ANA staining pattern.


CONCLUSIONS
The sensitivity of F-ANA at an abnormal titer was surprisingly low (76%) in established cases of SLE. ANSA occurred in 56% of the SLE sera, but also in a fair number (20%) of RA sera. Practically all ANSA-positive SLE sera were identified by chromosomal F-ANA staining. We conclude that the antigen-specific antinucleosomal EIA does not have high enough diagnostic specificity to justify use of this analysis for routine diagnostic purposes.
Sjöwall
Christopher
C
Division of Rheumatology, Autoimmunity and Immune Regulation unit (AIR) and Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping University Hospital, Linköping, Sweden.
Sturm
Martin
M
Dahle
Charlotte
C
Bengtsson
Anders A
AA
Jönsen
Andreas
A
Sturfelt
Gunnar
G
Skogh
Thomas
T
D000328:Adult; D000974:Antibodies, Antinuclear / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D012680:Sensitivity and Specificity; D055815:Young Adult
D000974:Antibodies, Antinuclear; D015415:Biomarkers