Anti-perinuclear factor compared with the so called "antikeratin" antibodies and antibodies to human epidermis filaggrin, in the diagnosis of arthritides.
OBJECTIVE
Antiperinuclear factor (APF), "antikeratin antibodies" ("AKA"), and antibodies to human epidermis filaggrin (AFA), are highly specific serological markers of rheumatoid arthritis (RA), which recognise epitopes on various isoforms of (pro)filaggrin. It was proposed that these antibodies are globally named antifilaggrin autoantibodies. Here the diagnostic value of the detection of each one is compared and the overlap between the three tests evaluated.


METHODS
492 serum samples were tested, including 279 RA serum samples, taken from patients in France and Belgium. APF and "AKA" titres were estimated by indirect immunofluorescence, and AFA titres by immunoblotting on filaggrin enriched human epidermis extracts.


RESULTS
By a convenient choice of the positivity thresholds, the diagnostic sensitivity and specificity of the tests were shown to be similar (0.52 and 0.97, respectively). Although the antibody titres were strongly correlated, the associations APF-AFA or AFA-"AKA" permitted more than 52% or 55% of RA to be diagnosed, with a specificity of 0.99.


CONCLUSIONS
APF, "AKA", and AFA detection have a similar diagnostic value. However, because the three tests do not totally overlap, associating APF with "AKA" or AFA with "AKA" can improve diagnostic sensitivity. None of the three antigens used bear all the epitopes recognised by antifilaggrin autoantibodies.
Vincent
C
C
Department of Biology and Pathology of the Cell, INSERM CJF 96-02, IFR 30, Purpan Medical School, University of Toulouse III, France.
de Keyser
F
F
Masson-Bessière
C
C
Sebbag
M
M
Veys
E M
EM
Serre
G
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000974:Antibodies, Antinuclear / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000175:diagnosis*; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D004817:Epidermis / Q000276:immunology; D005260:Female; D000091344:Filaggrin Proteins; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007381:Intermediate Filament Proteins / Q000276:immunology*; D007633:Keratins / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity
D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D015415:Biomarkers; C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; C030902:antiperinuclear factor; D007633:Keratins