Overall, all IFN types showed lower ICCs compared to body weight, which was the most stable parameter during follow-up (ICC [95% CI], 0.975 [0.962, 0.982] p < 0.0001), but were comparable to the SLE disease activity index (SLEDAI; ICC [95% CI], 0.319 [0.169, 0.464]) (Figure 2A), suggesting that, similar to disease activity, IFN levels are variable during the course of SLE. This evidence concerns the gene IFNA1 and systemic lupus erythematosus.