Objectives: The prevalence of inflammatory back pain (IBP) and radiographic sacroiliitis in patients with rheumatoid arthritis (RA) was investigated in this study. It was also aimed to estimate the frequency of RA patients who also fulfilled the European Spondyloarthropathy Study Group (ESSG) criteria and/or Amor criteria for the classification of spondyloarthritis (SpA) and/or the modified New York criteria for the classification of ankylosing spondylitis (AS).

Methods: 167 patients with RA followed by an outpatient clinic of rheumatology at a university hospital in Izmir, a city located in western Turkey, were included in the study. All patients fulfilled ``the American Rheumatism Association 1987 revised criteria for the classification of RA''. A rheumatologist and two rheumatology fellows, using a standard questionnaire, obtained a detailed medical history and performed a complete physical examination in each of 167 patients with RA. Standard pelvic X-rays for examination of the sacroiliac joints were also ordered in all the patients. The X-rays were read blindly by an experienced rheumatologist and reported according to the established grading system. In subjects whose pelvic X-rays showed suspicion of sacroiliitis, a computed tomography (CT) or magnetic resonance imaging (MRI) was ordered to help in reaching a final consensus. In addition, in patients with IBP but who have normal pelvic radiographies, MRI of sacroiliac joint (SIJ) was performed. In subjects whose CT or MRI investigations showed suspicion of sacroiliitis, opinion of an experienced radiologist was obtained.

Results: Of the 167 RA patients included in the study, 135 were female (80.8%) and 32 were male (19.2%) with a mean age of 54.81±11.67 years. The mean disease duration was 9.80±9.40 years and the mean age at diagnosis was 46.09±13.00. The numbers of patients with positive rheumatoid factor (RF) were 126 (79.2%) and positive anti-cyclic citrullinated peptide antibody (anti-CCP) were 120 (81.1%). The average titers of RF and anti-CCP were 141.77 IU/mL and 147.65 RU/mL respectively. Twenty eight patients with RA (16.8%) had IBP. Pelvic radiography could be performed in 164 patients with RA and 4 of these patients (2.4%) were reported to have bilateral grade 3 sacroiliitis. CT and MRI of SIJ were performed in 19 RA patients and 23 RA patients, respectively. CT in 3 patients (1.8%) and MRI in 6 (3.6%) demonstrated presence of sacroiliitis. Two of 4 RA patients with radiographic sacroiliitis met the modified New York criteria for the classifying of AS. There was an additional patient with history of psoriasis who fulfilled the modified New York criteria for AS. All these patients had characteristic clinical, radiological and laboratory findings of RA. There were 15 patients with IBP but who had normal pelvic radiographies. MRI of SIJ could be performed in 12 of these patients and 3 patients showed sign of sacroiliitis. Thirty one patients with RA (18.6%) fulfilled the ESSG criteria (5 with positive MRI finding) and 26 (15.6%) Amor criteria (5 with positive MRI finding) for the classification of SpA (15 patients (9%) fulfilled both of these criteria sets).

Conclusion: This study suggests that the coexistence of RA and AS in the same patient may occur more frequently than reported. Interestingly, the prevalence of SpA according the ESSG and Amor classification criteria in RA patients was found to be much higher than in the general population. Axial involvement in patients with RA may be more common than expected.

Disclosure of Interest: NON DECLARED