Objective Low hydroxychloroquine (HCQ) blood levels are predictors of flare in adult lupus. Childhood-onset systemic lupus erythematosus (cSLE) has high morbidity with renal involvement in up to 80% of cases. The aim of this study is to determine the HCQ cut-off levels which predicts flare in childhood-onset lupus nephritis (LN). Methods Sixty LN patients on HCQ use for at least 6-months were prospectively evaluated at baseline (BL) and about 6-months later for cSLE flare and HCQ blood levels (ng/mL) measured by liquid chromatography-tandem mass spectrometry. Results There were 19 patients (32%) with flare, during the study with median SLEDAI increase of 4 (0–8). Median (IQR) BL HCQ levels of the flare group were lower compared to stable patients [557.5 (68.6–980.3) vs. 1061.9 (534.8–1590.0 ng/mL); p=0.012]. ROC curve analysis demonstrated that HCQ levels≤1075 ng/mL were associated with a 5.08 (95%CI 1.28-20.13; p=0.021) times increased risk of flare. Six-month HCQ levels revealed that most patients 24/54 (44%) had persistently low levels (≤1075) during follow-up. Among those, 11/24 (46%) had flare. Multiple logistic regression analysis including prednisone use, baseline SLEDAI-2K, adherence based on pharmacy refill and BL HCQ blood levels as possible predictors of flare revealed that only HCQ blood level was independently associated with flare (OR 0.999, 95%CI 0.998-1.0, p=0.013). Conclusions We demonstrated that HCQ blood cut-off level under 1075 ng/mL predicts flare in childhood-onset LN patients under prescribed HCQ dose of 4.0–5.5 mg/kg/day. We further observed that most of these patients have compliance issues reinforcing the need for a close surveillance particularly in those with levels below the defined cut-off.

Introduction Influenza A (H3N2) virus is the most important cause of seasonal influenza morbidity and mortality in the last 50 years, surpassing the impact of H1N1. Data assessing immunogenicity and safety of this virus component are lacking in systemic lupus erythematosus (SLE) and restricted to small reports with other H3N2 strains. Objective This study aims to evaluate short-term immunogenicity and safety of influenza A/Singapore (H3N2) vaccine in SLE. Methods 81 consecutive SLE patients and 81 age- and sex-matched healthy controls (HC) were vaccinated with the influenza A/Singapore/INFIMH-16-0019/2016(H3N2)-like virus. Seroprotection (SP) and seroconversion (SC) rates, geometric mean titers(GMT), and factor increase in GMT(FI-GMT) and adverse events were assessed before and 4 weeks post-vaccination. Disease activity and therapies were also evaluated. Results Before immunization, SLE and HC groups had high SP rates (89% vs 77%, p = 0.061) and elevated GMT titer with higher levels in SLE (129.1(104.1–154.1) vs 54.8(45.0–64.6), p < 0.001). Frequency of two previous years’ influenza vaccination was high and comparable in SLE and HC (89% vs 90%, p = 1.000). Four weeks post-vaccination, median GMT increased for both groups and remained higher in SLE compared to HC (239.9(189.5–290.4) vs 94.5(72.6–116.4), p < 0.0001) with a comparable FI-GMT (2.3(1.8–2.9) vs 1.9(1.5-2.3), p = 0.051). SC rates were low and comparable for both groups (16% vs 11%, respectively, p = 0.974). Disease activity scores remained stable throughout the study ( p = 1.000) and severe adverse events were not identified. Conclusion Influenza A/Singapore (H3N2) vaccine has an adequate safety profile. The distinct immunogenicity pattern from other influenza A components characterized by a remarkably high pre- and post-vaccination SP rate and high GMT levels may be associated with previous influenza A vaccination. ( www.clinicaltrials.gov , NCT03540823).

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