The Evaluation Of Disease Activity In Patients With Ankylosing Spondylitis

BackgroundAnkylosing spondylitis (AS) is a chronic, inflammatory arthritis that predominantlyaffects the axial skeleton. Patients with AS differ in the predominance of individualclinical manifestations. This phenotypic heterogeneity of the disease makes theevaluation of disease activity really complex. But the evaluation of disease activity isimportant for treatment decision and evaluate drug efficacy. Currently used measuressuch as ESR,CRP and BASDAI have limitations because they either measure only oneaspect of the disease, have low sensitivity or are fully patient orientated.50-70%of ASpatients do not have peripheral manifestations, disease activity in such patients might beassessed at a low level. Therefore, the Assessment of Spondyloarthritis internationalSociety (ASAS) developed a new assessment tool of disease activity in AS: ankylosingspondylitis disease activity score (ASDAS). It is the first instrument that covers themost important aspects of disease assessment in AS (patients orientated subjectiveassessment and objective laboratory test).So far, there are two studies abroad showingthat the ASDAS is highly discriminatory in differentiating patients with different levelsof disease activity and patients with different levels of change in comparison to theBASDAI. However, there is no similar study on it in China. Besides, we furthercompare the modified version of theBASDAI with the original BASDAI in evaluatingdisease activity of patients without peripheral arthritis.Objective 1. To investigate the value of ASDAS in evaluating disease activity of AS patients inChina in comparison to the traditional indices: BASDAI, ESR, CRP, patient globalassessment, physician global assessment and treatment decision.2. Compare the modified version of theBASDAI with the original BASDAI inevaluating disease activity of patients without peripheral arthritis.Method1. ASDAS and BASDAI were used to evaluate disease activity of patients with AS.Patient global scores, physician global scores and treatment decision were regarded as―gold standard‖for disease activity in this study. The patients were divided into2groups: low and high disease activity according to the "gold standard". Two differentformulae for ASDAS were commonly used: one included ESR (ASDAS-ESR),the otherincluded CRP (ASDAS-CRP). Statistical analysis included descriptive statistics, linearcorrelation and regression and receiver operating curve (ROC) curve with SPSS12.0.2. Patients were divided into a "P+" group if peripheral manifestations were present anda "P-" group if without peripheral manifestations. BASDAI was used to evaluatedisease activity of patients with ankylosing spondylitis, and then calculated themini-BASDAI by omitting both the peripheral joints and the enthesitis questions:questions3and4.Results1①Correlation analysis: Both ASDAS and BASDAI correlated significantly withpatient global assessment. ASDAS-ESR: r=0.698, p=0.000, ASDAS-CRP: r=0.725,p=0.000, BASDAI: r=0.713, p=0.000. But in correlating with ESR and CRP, thecorrelation was weaker, ESR: r=0.174, p=0.001, CRP: r=0.206, p=0.005. ASDAS andBASDAI correlated significantly with physician global assessment. ASDAS-ESR:r=0.782, p=0.000, ASDAS-CRP: r=0.847, p=0.000, BASDAI: r=0.771, p=0.000. Butin correlating with ESR and CRP, the correlation was weaker, ESR: r=0.379, p=0.000, CRP: r=0.410, p=0.000.②The explanatory ability of ASDAS and BASDAI for thedisease activity of AS patients,in the setting of patient global assessment based, the R2of ASDAS and BASDAI were0.522and0.516, while in in the setting of physicianglobal assessment based, the R2of ASDAS and BASDAI were0.718and0.599.Thatis,the ASDAS outperformed the BASDAI.③The accurancy of evaluating diseaseactivity of AS patients,ASDAS-CRP has the best accurancy,the AUC is0.849, thenext is ASDAS-ESR, the AUC is0.845, the last is BASDAI, the AUC is0.832.Therefore,the accurancy of the ASDAS was proved to be better than that of theBASDAI.2. Patients with peripheral involvement had higher disease activity in all activityparameters. The mini-BASDAI had higher values compared with the original BASDAIin both groups. However, the mini-BASDAI did not correlate better with othermarkers of disease activity compared with the original BASDAI.Conclusion1.In comparison to the currently used disease activity indices, ASDAS is a newpromising tool for evaluating disease activity, and is worth clinical application.2. The mini-BASDAI did not result in an advantage to assess disease activity in patientswithout peripheral manifestations.