Low-grade radiographic sacroiliitis as prognostic factor in patients with undifferentiated spondyloarthritis fulfilling ankylosing spondylitis diagnostic criteria throughout follow-up

Gabriela Huerta-Sil ¹, Julio Casasola-Vargas ¹, John D Londoño ², Rodolfo Ruíz-Rivas ³, José Chávez ⁴, César Pacheco-Tena ⁵, Mario Cardiel ⁶, Gilberto Vargas-Alarcón ⁷ and Rubén Burgos-Vargas ^8*

¹ Hospital General de México, Mexico
² Clinica Universitaria Teleton, Universidad de la Sabana. Bogotá, Colombia
³ Hospital de Pediatría, Centro Médico Nacional Siglo XXI, Mexico
⁴ Hospital E. Rebagliati. Lima, Peru
⁵ Facultad de Medicina, Universidad Autónoma de Chihuahua. Chihuahua, Mexico
⁶ Hospital General Dr. Miguel Silva. Morelia, Mexico
⁷ Instituto Nacional de Cardiologia, Mexico
⁸ Hospital General de México. Universidad Nacional Autónoma de México., Mexico

^* To whom correspondence should be addressed. E-mail: burgosv{at}prodigy.net.mx.

Accepted 2 October 2005

Abstract

Objective: To determine the rate and factors associated with ankylosing spondylitis (AS) in a cohort of patients with undifferentiated spondyloarthritides (SpA).

Patients and methods: Sixty-two consecutive patients with undifferentiated SpA seen between 1998 and 1999 underwent clinical and imaging evaluations through follow-up. The diagnosis of AS was the outcome.

Results: Fifty patients (26 males, age at onset 20.4 ± 8.8 years; disease duration 5.4 ± 5.7 years) having peripheral arthritis (n=35) and inflammatory back pain (n=24) at onset were followed-up for 3 to 5 years. At baseline, >90% patients had axial and peripheral disease, 38% radiographic sacroiliitis below the cut-off level for AS diagnosis, BASDAI of 3.9, and BASFI of 2.9. At last evaluation, 21 (42%) patients had AS. Two prognostic factors were identified associated with the diagnosis of AS in the multivariate analysis: radiographic sacroiliitis grade <2, bilateral or grade <3, unilateral (OR 11.179 [95% CI 2.59, 48.16]; p=0.001), particularly grade 1, bilateral (OR 12.58 [95% CI 1.33, 119.092]; p=0.027), and previous uveitis (OR 19.25 [95% CI 1.72, 214.39]; p=0.001). In addition, we found a trend for acute phase reactants levels, juvenile onset, and HLA-B27, but no significant associations with AS.

Conclusions: Low grade radiographic sacroiliitis is a prognostic factor for AS in patients originally classified as undifferentiated SpA. We propose in this context that low grade radiographic sacroiliitis should be regarded as indicative of early AS in patients with undifferentiated SpA

Keywords: Ankylosing spondylitis., sacroiliitis., spondyloarthritis., spondyloarthropathies., uveitis

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