Automated immunoassays for the autoantibodies to carbamylated or citrullinated telopeptides of type I and II collagens.
BACKGROUND
The aim of the study was to describe automated immunoassays for autoantibodies to homocitrulline or citrulline containing telopeptides of type I and II collagen in various disease categories in an early arthritis series.


METHODS
Serum samples were collected from 142 patients over 16 years of age with newly diagnosed inflammatory joint disease. All samples were analyzed with an automated inhibition chemiluminescence immunoassay (CLIA) using four different peptide pairs, each consisting of a biotinylated antigen and an inhibiting peptide. Assays were performed with an IDS-iSYS analyzer. Autoantibodies binding to homocitrulline and citrulline containing C-telopeptides of type I (HTELO-I, TELO-I) and type II collagens (HTELO-II, TELO-II) were analyzed.


RESULTS
The mean ratio of HTELO-I inhibition in seropositive and seronegative rheumatoid arthritis (RA) was 3.07 (95% CI 1.41-11.60), p=0.003, and in seropositive and seronegative undifferentiated arthritis (UA) 4.90 (1.85-14.49), p<0.001. The respective mean ratios in seropositive and seronegative RA and UA were in TELO-I 8.72 (3.68-58.01), p<0.001 and 3.13 (1.49-6.16), p=0.008, in HTELO-II 7.57 (3.18-56.60), p<0.001 and 2.97 (1.23-6.69), p=0.037, and in TELO-II 3.01 (1.30-9.51), p=0.002 and 3.64 (1.86-7.65), p=0.008. In reactive arthritis, ankylosing spondylitis, psoriatic arthritis and unspecified spondyloarthritis the inhibition levels were similar to those observed in seronegative RA or UA.


CONCLUSIONS
Autoantibodies binding to homocitrulline or citrulline containing telopeptides of type I and II collagen did not differ significantly. They were highest among patients with seropositive disease and they differentiated seropositive and seronegative arthritis.
Jere
J
Häyrynen
Maija
M
Kärkkäinen
Aulikki
A
Kononoff
Leena
L
Arstila
Pia
P
Elfving
Helena
H
Niinisalo
Elina
E
Savolainen
Hannu
H
Kautiainen
Juha
J
Risteli
Oili
O
Kaipiainen-Seppänen
Marja-Kaisa
MK
Koivula
D000328:Adult; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D001331:Automation; D002956:Citrulline / Q000031:analogs & derivatives* / Q000378:metabolism; D024042:Collagen Type I / Q000737:chemistry*; D024043:Collagen Type II / Q000737:chemistry*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000276:immunology* / Q000378:metabolism*
D001323:Autoantibodies; D024042:Collagen Type I; D024043:Collagen Type II; D010446:Peptide Fragments; C001352:homocitrulline; D002956:Citrulline