Hydroxychloroquine discontinuation in systemic lupus erythematosus: a retrospective cohort study with 3-year follow-up.

OBJECTIVES To evaluate the incidence and factors associated with systemic lupus erythematosus (SLE) flares following hydroxychloroquine (HCQ) discontinuation. METHODS We conducted a retrospective single-centre study of adult SLE patients who discontinued HCQ. Clinical and serological characteristics at baseline (time of HCQ discontinuation), were compared between patients who experienced flares (any, repeated, or severe) and those who remained flare-free during the follow-up, with a potential observation period of up to 36 months. Categorical variables were analysed using Fisher's exact test; continuous variables using appropriate tests based on normality and variance. RESULTS Among 42 patients included, 12 (29%), 15 (36%), and 14 (38%) experienced a flare during the first, second, and third year, respectively. Over 36 months, 21 (50%) had at least one flare, 10 had a severe flare, and 8 had repeated flares. 19 patients remained flare-free. Low C3 levels at baseline were associated with any flare (p< 0.001), repeated flares (p< 0.001), and severe flares (p= 0.014) compared with those without flares. Patients with low C3 at baseline flared earlier and more frequently (log-rank p< 0.001) with hazard ratio of 10.18 (95%CI: 3.26-31.84, p< 0.001) for flaring, compared with those with normal C3. Other clinical and laboratory factors were not associated with flare prevention. CONCLUSION Half the patients who discontinued HCQ flared within two years. Low C3 levels at baseline were associated with increased risk of flares. These findings suggest that flares are common soon after HCQ discontinuation, and low C3 may help identify patients at higher risk for disease reactivation after HCQ discontinuation.