Statistical analysis
All the data was coded anonymously. The Shapiro-Wilk test confirmed that all data were normally distributed. Missing value analysis confirmed that missing data was randomly distributed and excluded for the comparisons. Descriptive statistics for each group were analysed and reported in the results with their mean (SD); independent sample t-test was used to compare the group means. Pearson’s correlation analysis were used to compute the correlation between the two methods in each group, and Bland-Altman plot analysis used to estimate the agreement within the axSpA cohort. Correlation coefficients 1.00 to 0.90 were interpreted as very strong, 0.89 to 0.70 as strong, 0.69 to 0.50 as moderate, 0.49 to 0.30 as weak, and 0.29 to 0 as very weak. Frequencies and percentages were used to summarise the feasibility data. P values <0.05 were considered statistically significant, and all tests were 2-tailed. Statistical analyses were performed using SPSS version 28 (IBM SPSS Statistics).