Use of a commercial line blot assay as a screening test for autoantibodies in inflammatory myopathies.
OBJECTIVE
To evaluate the clinical utility of a commercial immunoblot assay for the detection of myositis-specific autoantibodies.


METHODS
Serum samples from 153 myositis patients and 77 disease controls were investigated. The commercial Euroline assay with seven autoantigens (Mi-2, Ku, PM-Scl, Jo-1, Pl-7, Pl-12 and SSA/Ro-52) was used according to the manufacturer s instructions, and supplemented with an anti-SRP strip. In a separate experiment analyses were performed at different temperatures. Results were recorded with densitometry.


RESULTS
Anti-Jo-1 was found in 18 myositis and one systemic sclerosis patient. Antibodies against Mi-2 were found in 5 myositis patients, and eleven myositis patients had antibodies against PM-Scl. Four myositis patients showed anti-Pl-7 reactivity, whereas no patients had antibodies against Pl-12. Anti-Ku antibodies were found in 4 myositis and 2 primary Sjögren's syndrome patients. Anti-SRP was found in 8 myositis patients as well as in two disease controls. Antibodies against SSA/Ro52 ranged between 23-62% in all groups except juvenile dermatomyositis patients. Most autoantibody reactivities were clearly positive, only 11% (14/127) were borderline positive. Higher assay temperature increased antibody reactivities.


CONCLUSIONS
Except for anti-SSA/Ro-52 and anti-Ku the antibody reactivities were rather myositis-specific, supporting the use of this immunoblot assay. However, assay validation needs to be determined against other methods.
Rönnelid
Johan
J
Unit of Clinical Immunology, Uppsala University and Uppsala University Hospital, SE-75185 Uppsala, Sweden. johan.ronnelid@klinimm.uu.se
Barbasso Helmers
Sevim
S
Storfors
Helena
H
Grip
Katarina
K
Rönnblom
Lars
L
Franck-Larsson
Karin
K
Nordmark
Gunnel
G
Lundberg
Ingrid E
IE
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood; D001324:Autoantigens / Q000276:immunology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D015151:Immunoblotting; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009220:Myositis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D012595:Scleroderma, Systemic / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D012680:Sensitivity and Specificity; D013696:Temperature
D001323:Autoantibodies; D001324:Autoantigens