The potential use of antibacterial peptide antibody indices in the diagnosis of rheumatoid arthritis and ankylosing spondylitis.
BACKGROUND
Both rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are potentially disabling arthritic disorders for which as yet no highly sensitive and reliable diagnostic laboratory markers are available.


OBJECTIVE
The objective of this study was to evaluate the levels of antibodies against Proteus and Klebsiella antigenic peptides in an endeavor to develop diagnostic indices for the identification of patients with RA and AS, respectively.


METHODS
Sera from 50 patients with RA, 34 patients with AS, and 38 healthy subjects were screened for antibodies against "ESRRAL" and "IRRET" synthetic amino acid peptides obtained from Proteus hemolysin and urease (HU) as well as against "QTDRED" and "DRDE" peptides from Klebsiella nitrogenase and pullulanase (NP) proteins, respectively. Multiplication of the 2 antibodies against each organism produced indices for RA-HU and AS-NP.


RESULTS
Significantly increased levels of anti-HU antibodies (P<0.0001) were observed in patients with RA when compared with patients with AS or with healthy control subjects. Patients with AS were found to have significantly elevated levels of anti-NP (P<0.0001) antibodies when compared with patients with RA or with healthy subjects. Furthermore, all patients with RA were found to have values of anti-HU antibody (RA-HU) index above 95% confidence limit (CL) of the mean of healthy control subjects; meanwhile, all patients with AS were having values of anti-NP antibody (AS-NP) index above the 95% CL of the mean of healthy control subjects (100% sensitivity). However, the specificity of the RA-HU index in RA and the AS-NP index in patients with AS were 92% and 95%, respectively.


CONCLUSIONS
The use of the RA-HU or AS-NP diagnostic index as a sole marker or in combination with other autoantibody markers could be used in the identification of patients with RA or AS, respectively. Longitudinal investigations starting with patients with early disease will be needed.
Rashid
Taha
T
Division of Health and Life Sciences and the Department of Pharmacy, King's College London, and the Department of Rheumatology, University College Medical School, Middlesex Hospital, London, UK.
Ebringer
Alan
A
Wilson
Clyde
C
Bansal
Sukvinder
S
Paimela
Leena
L
Binder
Allan
A
D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000382:microbiology; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007132:Immunoglobulin Isotypes / Q000276:immunology; D007709:Klebsiella / Q000201:enzymology / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D011511:Proteus / Q000201:enzymology / Q000276:immunology*; D013167:Spondylitis, Ankylosing / Q000097:blood* / Q000382:microbiology
D000907:Antibodies, Bacterial; D007132:Immunoglobulin Isotypes; D010455:Peptides