title: Serum amyloid a as a useful indicator of disease activity in patients with ankylosing spondylitis.
abstract: OBJECTIVE
  To investigate whether serum amyloid A (SAA) levels are increased in patients with ankylosing spondylitis (AS) and whether its levels correlate well with AS disease activity.
  
  
  METHODS
  Thirty-eight patients with AS and 38 age- and sex-matched control subjects were enrolled in this cross-sectional study. Their SAA levels were quantitatively measured by immunonephelometry. An established, self-administered instrument for evaluating disease activity (Bath Ankylosing Spondylitis Disease Activity Index, BASDAI) was used to measure and acute phase reactants, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), in patients with AS.
  
  
  RESULTS
  Patients with AS had a significantly higher mean SAA level than controls (9.52 +/- 7.49mg/L versus 2.73 +/- 1.57mg/L, p < 0.05), and the mean BASDAI score of patients with elevated SAA levels was significantly higher than that of patients with normal SAA levels (5.6 +/- 1.3 versus 4.4 +/- 1.5, p < 0.05). SAA levels showed significant correlations with BASDAI scores (r=0.431, p=0.007), ESR (r=0.521, p=0.001) and CRP levels (r=0.648, p < 0.001). Additionally, the correlation between ESR and CRP levels also appeared significant (r=0.703, p < 0.001). In those with normal ESR or CRP levels, SAA levels and BASDAI scores were elevated (p < 0.05) and showed a trend of positive correlation with one another.
  
  
  CONCLUSIONS
  Our data showed that SAA levels were increased in patients with AS and correlated well with disease activity. These findings suggest that SAA can be used as a valuable indicator of disease activity in AS.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, 134 Sinchon-Dong, Seodaemun-Gu, Seoul, Korea.
authors.forename: Sang Youn
authors.initials: SY
authors.lastname: Jung
authors.forename: Min-Chan
authors.initials: MC
authors.lastname: Park
authors.forename: Yong-Beom
authors.initials: YB
authors.lastname: Park
authors.forename: Soo-Kon
authors.initials: SK
authors.lastname: Lee
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D001799:Blood Sedimentation; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007249:Inflammation; D008297:Male; D012016:Reference Values; D000685:Serum Amyloid A Protein / Q000378:metabolism*; D013167:Spondylitis, Ankylosing / Q000097:blood* / Q000150:complications / Q000175:diagnosis
chemical_list: D015415:Biomarkers; D000685:Serum Amyloid A Protein