RÉSUMÉ
Serum amyloid A [SAA] has been reported to be more sensitive than C-reactive protein [CRP] as a marker of disease activity. It may function in immune regulation and is linked to the development of secondary amyloidosis. We investigated SAA in ankylosing spondylitis patients and compared it with CRP, erythrocyte sedimentation rate [ESR] and interleukin [IL]-6 in relation to disease activity. Using a sensitive and specific ELISA, SAA and IL-6 were measured in the serum of 25 patients with ankylosing spondylitis and in 20 subjects control group. CRP, ESR and clinical disease activity using Bath Ankylosing Spondylitis Disease Activity Index [BASDAI] were also recorded. Patients with AS had a significantly higher mean SAA level than controls [96.34 ug/ml, versus 3.84 ug/ml. p<0.001]. Serum IL-6 had significantly higher level in AS patients than in controls. Although statistical significance was not found, the mean BASDAI score of patients with elevated SAA levels was higher than that of patients with normal SAA levels. It was found that SAA showed significant correlation with ESR, CRP, IL-6 and BASDAI score. Additionally, the correlation between IL-6 and both ESR and CRP appeared to be significant but no significant correlation was found between IL-6 and BASDAI score. In patients with normal ESR and CRP levels, SAA levels showed positive significant correlation with BASDAI score. SAA seems to be an additional very useful disease activity marker used in monitoring of ankylosing spondylitis patients