International Journal of Preventive Medicine (Int J Prev Med)2008-78021262021101324752475ENDepartment of Internal Medicine, School of Medicine, Isfahan University of Medical Sciences, IsfahanDepartment of Internal Medicine, School of Medicine, Isfahan University of Medical Sciences, IsfahanDepartment of Surgery, Westchester Medical Center, New York Medical College, New York20211013<p><strong>Background</strong>: We aimed to determine the sensitivity of serum cystatin C (Cys‑C) in predicting lupus flare‑up.</p><p><strong>Methods</strong>: In a longitudinal study, 77 patients were followed‑up for up to 15 months. Cys‑C, physician global assessment (PGA), and lupus activity index (SLEDAI) were recorded during each visit. Flare‑up was defined as an increase ≥4 scores in SLEDAI compared to the last visit. The predictability of flare‑up by Cys‑C was evaluated by generalized linear‑mixed effect model (GLMM) and generalized estimating equation (GEE). Predictive power of Cys‑C, SLEDAI, and PGA was compared by the area under the curves (AUC) and application of receiver operating characteristic (ROC) curves.</p><p><strong>Results</strong>: Lupus flare‑up was observed in 14 out of 77 patients on the 1st visit, 3 out of 41 patients on the 2nd visit, 2 out of 26 patients on the 3rd visit, 1 out of 14 patients on the 4th visit, and 1 out of 3 patients on the 5th visit. Mean Cys‑C levels in patients with flare‑up vs. those with no flare‑up in the 1st, 2nd, and 3rd visits were 1769 vs. 1603 (P = 0.6), 5701 vs. 2117 (p = 0.2) and 1409 vs. 1731 (p = 0.9), respectively. Cys‑C had lower predictive power than PGA and SLEDAI for either flare‑up, active nephritis or SLEDAI in GLMM/GEE models. Cys‑C also showed lower sensitivity (AUC = 0.701, 95%CI = 0.579‑0.823, P = 0.003) than PGA and SLEDAI, to distinguish patients prone to flare‑ups.</p><p><strong>Conclusions</strong>: Although Cys‑C had some sensitivity for predicting flare‑up, active nephritis or SLEDAI, its sensitivity was lower than that in PGA and SLEDAI.</p>http://ijpm.mui.ac.ir/index.php/ijpm/article/view/2475http://ijpm.mui.ac.ir/index.php/ijpm/article/download/2475/717718315