Circulating CD14⁺⁺CD16⁺ Monocyte Subsets as a Surrogate Marker of the Therapeutic Effect of Corticosteroid Therapy in Patients With Cardiac Sarcoidosis

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Background:We aimed to evaluate whether specific monocyte subsets could serve as surrogate markers of disease activity in cardiac sarcoidosis (CS) evaluated by ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (¹⁸F-FDG PET).Methods and Results:We studied 28 patients with CS (8 men; mean age: 61±9 years) diagnosed according to consensus criteria. We divided the patients into 2 groups: known CS receiving corticosteroid therapy (Rx(+); n=13) and new-onset CS (Rx(−); n=15), and analyzed 3 distinct monocyte subsets (CD14⁺CD16⁻, CD14⁺⁺CD16⁺, and CD14⁺⁻CD16⁺). Monocyte subsets were also analyzed in 10 Rx(−) patients before and 12 weeks after starting corticosteroid therapy. Inflammatory activity was quantified by ¹⁸F-FDG PET using the coefficient of variation (COV) of the standardized uptake value (SUV). The proportion of CD14⁺⁺CD16⁺monocytes in Rx(+) patients (10.8 [0.2–23.5] %) was significantly lower than in Rx(−) patients (23.0 [11.5–38.4] %, P=0.001). After corticosteroid therapy, the COV of the SUV was significantly improved from 0.32 [0.14–0.62] to 0.17 [0.04–0.43] (P=0.017). The proportion of CD14⁺⁺16⁺monocytes showed a significant decrease from 22.2 [8.8–38.4] % to 8.4 [1.8–16.8] % (P=0.001). The decrease in the proportion of CD14⁺⁺16⁺monocytes significantly correlated with the decrease in the COV of the SUV (r=0.495, P=0.027).Conclusions:CD14⁺⁺16⁺monocytes are a possible surrogate marker of the therapeutic effect of corticosteroid therapy in CS.