Background Over the last decades, many efforts have been conducted to develop useful tool for the evaluation of disease activity. However, since the development of Assessment of SpondyloArthritis international Society Health Index (ASAS HI), no specific freely available questionnaires to describe the overall picture of impairments, limitations and restrictions in activities or social partecipation.
Objectives The aims of this study were to test the feasibility, reliability, and construct validity of the ASAS HI, in order to compare its clinimetric properties with the current available measures of disease activity, functional limitation and health status assessments in patients with axSpA.
Methods A cohort of 140 consecutive axSpA has been the object of study. The feasibility has been determined by the percentage of patients who were able to complete the questionnaire by themselves and by the time employed to fill the ASAS HI. The reliability has been evaluated performing a test-rerest of the questionnaire within a week. The construct validity was examined in three ways. First, we examined construct convergent validity by correlating the scores of the ASAS HI with ASDAS-CRP/ESR, SASDAS, BASDAI, BASMI, BASFI, the ASQoL and EQ-5D. Secondly, we have created patient groups based on the patients' activity ranks (ASDAS-CRP and SASDAS categorisation) within the cohort to assess discriminative accuracy. Additionally, to distinguish patients with active and non-active disease and to assess their respective cut-off points values, the receiver operating characteristic (ROC) curve analysis was used. Thirdly, we analyzed the contribution of demographic (age, sex, and disease duration) and clinical variables (number of comorbidity and disease activity by ASAS-CRP) to the attainment of an ASAS HI condition by stepwise logistic regression.
Results The mean time to complete the ASAS HI was 114.9± 45.2 seconds (range 48 – 210 seconds). Coefficients of agreement between ASAS HI scores on first and second administrations were excellent and all items showed very good agreement (ICC =0.976; range 0.966 to 0.982). The ASAS HI was correlated significantly with all other comparator scores (p<0.0001). The highest correlations were seen with ASQoL (rho 0.784; p<0.0001), BASFI (rho 0.671; p<0.0001) and SASDAS (rho 0.640; p<0.0003). On categorizing patients into different cut-off point of disease activity, with respect to the both ASDAS-CRP and SASDAS, ASAS HI scores were highly significantly different between the four categories (p<0.0001). An ASAS HI value of 4.0 resulted the cut-off with the highest combination of sensitivity and specificity (82.6% and 86.3%, respectively) to distinguish the inactive disease.
Conclusions The results reported in this study confirm the feasibility, reliability and validity of the ASAS HI in Italian patients with axSpA. Of particular interest appears the cut-off value of 4.0, under which could be identified the inactive disease. This value could represent an easily applicable starting point in daily clinical practice.
Disclosure of Interest None declared