an increasing trendP = 0.031
The fluctuation of plasma levels of IgA anti-CD74 over time in r-axSpA in comparison with the fluctuation in controls Mixed-effects analysis of log IgA anti-CD74 levels, adjusting for BMI and ever smoker (at inclusion in Backbone), revealed an increasing trend in relation to age in the controls (β = 0.11; 95% CI: 0.01, 0.2; P = 0.031).