A study on calculating the ankylosing spondylitis disease activity score according to the C-reactive protein level / 中华内科杂志

ABSTRACT

Objective To study the prediction value of C-reactive protein (CRP) level to ankylosing spondylitis disease activity score (ASDAS),the most widely used activity score in ankylosing spondylitis (AS).Methods A total of 386 patients with AS were enrolled and divided into 2 groups by CRP≥3.5 mg/L (n =266) and CRP ＜ 3.5 mg/L(n =120).ASDAS-CRP was evaluated in patients with CRP below the normal range (3.5 mg/L) in different subgroups.Three methods were used to test the consistency between ASDAS-CRP and ASDAS-erythrocyte sedimentation rate (ESR).Results The ASDAS-CRP showed a good correlation with the ASDAS-ESR when CRP level was ≥ 3.5 mg/L (r =0.899,P =0.000).In the group of CRP ＜ 3.5 mg/L,ASDAS-ESR showed better consistency with ASDAS-CRP when CRP level was below 1.5 mg/L(intra-class correlation coefficient 0.902;kappa coefficient 0.70).By the evaluation of variant gradient matrix,CRP 1.5 mg/L coincided with disease activity states.Conclusion There is good consistency between ASDAS-CRP and ASDAS-ESR.When CRP level is below the normal range,1.5 mg/L could be a cut-off value to calculate the optimal ASDAS-CRP score.