Low grade radiographic sacroiliitis as prognostic factor in patients with undifferentiated spondyloarthritis fulfilling diagnostic criteria for ankylosing spondylitis throughout follow up.
OBJECTIVE
To determine the rate and factors associated with ankylosing spondylitis in a cohort of patients with undifferentiated spondyloarthritides (SpA).


METHODS
62 consecutive patients with undifferentiated SpA seen between 1998 and 1999 underwent clinical and imaging evaluations throughout follow up. The main outcome measure was a diagnosis of ankylosing spondylitis.


RESULTS
50 patients with peripheral arthritis (n = 35) and inflammatory back pain (n = 24) (26 male; mean (SD) age at onset, 20.4 (8.8) years; disease duration 5.4 (5.7) years) were followed up for 3-5 years. At baseline, >90% of patients had axial and peripheral disease, while 38% had radiographic sacroiliitis below the cut off level for a diagnosis of ankylosing spondylitis (BASDAI 3.9, BASFI 2.9). At the most recent evaluation, 21 patients (42%) had ankylosing spondylitis. Two factors were associated with a diagnosis of ankylosing spondylitis in multivariate analysis: radiographic sacroiliitis grade <2 bilateral, or grade <3 unilateral (odds ratio (OR) = 11.18 (95% confidence interval, 2.59 to 48.16), p = 0.001), particularly grade 1 bilateral (OR = 12.58 (1.33 to 119.09), p = 0.027), and previous uveitis (OR = 19.25 (1.72 to 214.39), p = 0.001). Acute phase reactant levels, juvenile onset, and HLA-B27 showed a trend to linkage with ankylosing spondylitis (NS).


CONCLUSIONS
Low grade radiographic sacroiliitis is a prognostic factor for ankylosing spondylitis in patients originally classified as having undifferentiated SpA. Low grade radiographic sacroiliitis should be regarded as indicative of early ankylosing spondylitis in patients with undifferentiated SpA.
Huerta-Sil
G
G
Department of Rheumatology, Hospital General de México, Dr Balmis 148, Mexico DF 06726.
Casasola-Vargas
J C
JC
Londoño
J D
JD
Rivas-Ruíz
R
R
Chávez
J
J
Pacheco-Tena
C
C
Cardiel
M H
MH
Vargas-Alarcón
G
G
Burgos-Vargas
R
R
D000293:Adolescent; D000328:Adult; D001168:Arthritis / Q000150:complications / Q000000981:diagnostic imaging; D018450:Disease Progression; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011379:Prognosis; D011859:Radiography; D012307:Risk Factors; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D012720:Severity of Illness Index; D025241:Spondylarthritis / Q000150:complications / Q000175:diagnosis*; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging; D014605:Uveitis / Q000150:complications