Comparison of Interleukin-6 Plasma Concentration in Multisystem Inflammatory Syndrome in Children Associated With SARS-CoV-2 and Pediatric Sepsis.

Importance: Multisystem Inflammatory Syndrome in Children (MIS-C) associated with SARS-CoV-2 infection is thought to be driven by a post-viral dysregulated immune response, where interleukin 6 (IL-6) might have a central role. In this setting, IL-6 inhibitors are prescribed as immunomodulation in cases refractory to standard therapy. Objective: To compare plasma IL-6 concentration between critically ill children with MIS-C and sepsis. Design: A retrospective cohort study from previously collected data. Setting: Individual patient data were gathered from three different international datasets. Participants: Critically ill children between 1 month-old and 18 years old, with an IL-6 level measured within 48 h of admission to intensive care. Septic patients were diagnosed according to Surviving Sepsis Campaign definition and MIS-C cases by CDC criteria. We excluded children with immunodeficiency or immunosuppressive therapy. Exposure: None. Main Outcome(s) and Measure(s): The primary outcome was IL-6 plasma concentration in MIS-C and sepsis group at admission to the intensive care unit. We described demographics, inflammatory biomarkers, and clinical outcomes for both groups. A subgroup analysis for shock in each group was done. Results: We analyzed 66 patients with MIS-C and 44 patients with sepsis. MIS-C cases were older [96 (48, 144) vs. 20 (5, 132) months old, p < 0.01], but no differences in sex (41 vs. 43% female, p = 0.8) compared to septic group. Mechanical ventilation use was 48.5 vs. 93% (p < 0.001), vasoactive drug use 79 vs. 66% (p = 0.13), and mortality 4.6 vs. 34.1% (p < 0.01) in MIS-C group compared to sepsis. IL-6 was 156 (36, 579) ng/dl in MIS-C and 1,432 (122, 6,886) ng/dl in sepsis (p < 0.01), while no significant differences were observed in procalcitonin (PCT) and c-reactive protein (CRP). 52/66 (78.8%) patients had shock in MIS-C group, and 29/44 (65.9%) had septic shock in sepsis group. Septic shock had a significantly higher plasma IL-6 concentration than the three other sub-groups. Differences in IL-6, CRP, and PCT were not statistically different between MIS-C with and without shock. Conclusions and Relevance: IL-6 plasma concentration was elevated in critically ill MIS-C patients but at levels much lower than those of sepsis. Furthermore, IL-6 levels don't discriminate between MIS-C cases with and without shock. These results lead us to question the role of IL-6 in the pathobiology of MIS-C, its diagnosis, clinical outcomes, and, more importantly, the off-label use of IL-6 inhibitors for these cases.

Pediatric Inflammatory Multisystem Syndrome Associated With SARS-CoV-2: A Case Series Quantitative Systematic Review.

ABSTRACT: Pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 (PIMS-TS) is infrequent, but children might present as a life-threatening disease. In a systematic quantitative review, we analyzed 11 studies of PIMS-TS, including 468 children reported before July 1, 2020. We found a myriad of clinical features, but we were able to describe common characteristics: previously healthy school-aged children, persistent fever and gastrointestinal symptoms, lymphopenia, and high inflammatory markers. Clinical syndromes such as myocarditis and Kawasaki disease were present in only one third of cases each one. Pediatric intensive care unit admission was frequent, although length of stay was less than 1 week, and mortality was low. Most patients received immunoglobulin or steroids, although the level of evidence for that treatment is low. The PIMS-ST was recently described, and the detailed quantitative pooled data will increase clinicians' awareness, improve diagnosis, and promptly start treatment. This analysis also highlights the necessity of future collaborative studies, given the heterogeneous nature of the PIMS-TS.