It is known that QTc length and QT dispersion correlate with disease activity and cytokine levels in both patients with SLE and patients with RA.7, 11, 30, 48–51 We used the SLEDAI-2K, DAS28-CRP and CRP levels (as well as IL-6 levels in the RA group) to estimate disease activity. Here, CRP is linked to rheumatoid arthritis.