Time to Positive Blood Cultures Among Critically Ill Children Admitted to the PICU.

OBJECTIVES: Our study aimed to assess the time to positivity (TTP) of clinically significant blood cultures in critically ill children admitted to the PICU. DESIGN: Retrospective review of positive blood cultures in patients admitted or transferred to the PICU. SETTING: Large tertiary-care medical center with over 90 PICU beds. PATIENTS: Patients 0-20 years old with bacteremia admitted or transferred to the PICU. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary endpoint was the TTP, defined as time from blood culture draw to initial Gram stain result. Secondary endpoints included percentage of cultures reported by elapsed time, as well as the impact of pathogen and host immune status on TTP. Host immune status was classified as previously healthy, standard risk, or immunocompromised. Linear regression for TTP was performed to account for age, blood volume, and Gram stain. Among 164 episodes of clinically significant bacteremia, the median TTP was 13.3 hours (interquartile range, 10.7-16.8 hr). Enterobacterales, Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus pneumoniae were most commonly identified. By 12, 24, 36, and 48 hours, 37%, 89%, 95%, and 97% of positive cultures had resulted positive, respectively. Median TTP stratified by host immune status was 13.2 hours for previously healthy patients, 14.0 hours for those considered standard risk, and 10.6 hours for immunocompromised patients (p = 0.001). Median TTP was found to be independent of blood volume. No difference was seen in TTP for Gram-negative vs. Gram-positive organisms (12.2 vs. 13.9 hr; p = 0.2). CONCLUSIONS: Among critically ill children, 95% of clinically significant blood cultures had an initial positive result within 36 hours, regardless of host immune status. Need for antimicrobial therapy should be frequently reassessed and implementation of a shorter duration of empiric antibiotics should be considered in patients with low suspicion for infection.

Healthcare Sustainability to Address Climate Change: Call for Action to the Infectious Diseases Community.

The US healthcare system's contribution to greenhouse gas emissions and climate change is disproportionately high and harms the public. Several medical specialties are now reassessing how they can mitigate healthcare's harmful environmental impact. Healthcare sustainability is broadly defined as measures to decrease greenhouse gas emissions, waste, and other pollutants generated during the healthcare delivery process. Prior efforts and programs by infectious diseases (ID) professionals, such as antimicrobial stewardship and infection prevention and control can form a framework for ID professionals to help apply this expertise to healthcare environmental sustainability more broadly. This call to action proposes strategies for ID societies and professionals to incorporate climate change education for trainees, increase research and funding opportunities in healthcare sustainability, and calls for action by ID societies to champion system changes to decrease greenhouse gas emissions.

"Give Me Five": The Case for 5 Days of Antibiotics as the Default Duration for Acute Respiratory Tract Infections.

Acute respiratory tract infections (ARTIs) account for most antibiotic prescriptions in pediatrics. Although US guidelines continue to recommend ≥10 days antibiotics for common ARTIs, evidence suggests that 5-day courses can be safe and effective. Academic imprinting seems to play a major role in the continued use of prolonged antibiotic durations. In this report, we discuss the evidence supporting short antibiotic courses for group A streptococcal pharyngitis, acute otitis media, and acute bacterial rhinosinusitis. We discuss the basis for prolonged antibiotic course recommendations and recent literature investigating shorter courses. Prescribers in the United States should overcome academic imprinting and follow international trends to reduce antibiotic durations for common ARTIs, where 5 days is a safe and efficacious course when antibiotics are prescribed.

Antimicrobial Stewardship and Improved Antibiotic Utilization in the Pediatric Cardiac Intensive Care Unit.

Background: We developed a multidisciplinary antimicrobial stewardship team to optimize antimicrobial use within the Pediatric Cardiac Intensive Care Unit. A quality improvement initiative was conducted to decrease unnecessary broad-spectrum antibiotic use by 20%, with sustained change over 12 months. Methods: We conducted this quality improvement initiative within a quaternary care center. PDSA cycles focused on antibiotic overuse, provider education, and practice standardization. The primary outcome measure was days of therapy (DOT)/1000 patient days. Process measures included electronic medical record order-set use. Balancing measures focused on alternative antibiotic use, overall mortality, and sepsis-related mortality. Data were analyzed using statistical process control charts. Results: A significant and sustained decrease in DOT was observed for vancomycin and meropenem. Vancomycin use decreased from a baseline of 198 DOT to 137 DOT, a 31% reduction. Meropenem use decreased from 103 DOT to 34 DOT, a 67% reduction. These changes were sustained over 24 months. The collective use of gram-negative antibiotics, including meropenem, cefepime, and piperacillin-tazobactam, decreased from a baseline of 323 DOT to 239 DOT, a reduction of 26%. There was no reciprocal increase in cefepime or piperacillin-tazobactam use. Key interventions involved electronic medical record changes, including automatic stop times and empiric antibiotic standardization. All-cause mortality remained unchanged. Conclusions: The initiation of a dedicated antimicrobial stewardship initiative resulted in a sustained reduction in meropenem and vancomycin usage. Interventions did not lead to increased utilization of alternative broad-spectrum antimicrobials or increased mortality. Future interventions will target additional broad-spectrum antimicrobials.

Antibiotic waste in a pediatric healthcare system: Wasting drugs that are in limited supply.

In a pediatric hospital system over 2 years, 58,607 doses of antibiotic were wasted, an average of 80 doses per day, including drugs in shortage nationwide. Approximately 50% of waste occurred within the first 2 days of admission or the day of discharge, with ampicillin being the most wasted drug (N = 7,789 doses).

Short-Course Empiric Antibiotics in Children Undergoing Allogeneic Hematopoietic Cell Transplantation.

Fever is common in children undergoing hematopoietic cell transplantation (HCT). Empiric antibiotic (EA) therapy is initiated and often continued until neutrophil engraftment. Prolonged antibiotic exposure reduces microbiome diversity and causes overgrowth of pathogenic organisms, leading to such complications as infections from antibiotic-resistant organisms and Clostridium difficile colitis. Shorter courses of EA therapy have been studied in adults undergoing HCT without significant safety concerns, but data in children are lacking. We instituted a single-center preintervention/ postintervention quality improvement (QI) project to assess the feasibility of short-course EA therapy for first fever in patients undergoing HCT. We aimed to reduce the median duration of broad-spectrum antibiotic use in eligible patients from 20 days in 2020 to 10 days in 2021. Patients were eligible for the intervention, limiting EAs to 7 days for first fever, if they were admitted for their first allogeneic HCT, were afebrile for >24 hours, had no infection requiring systemic treatment, and were hemodynamically stable. Outcome measures included days of EA therapy for first fever and total broad-spectrum antibiotic use during the period of hospitalization, defined as the time from the start of conditioning to 30 days after HCT or hospital discharge, whichever occurred first. Balancing measures included bloodstream infection (BSI), fever, and intensive care (ICU) admission within 3 days of stopping EA therapy. Project criteria were applied retrospectively to patients who underwent HCT in 2020 to construct a preintervention short-course-eligible cohort. During the intervention period, 41 patients underwent allogeneic HCT, of whom 17 (41%) were eligible for short-course EA therapy. Among eligible patients, the median age was 5.3 years, 47% had an underlying malignancy, and 88% received myeloablative conditioning. There were no differences in demographic or HCT characteristics between patients eligible for short-course EA during the intervention and preintervention period (n = 24). The short-course EA schedule was adhered to by 14 of the 17 eligible patients (82%). The duration of EA for first fever and total broad-spectrum antibiotic use was significantly decreased in the short-course EA-eligible patients compared to the preintervention cohort, from a median of 17 days to 8 days and from 20 days to 10 days, respectively (P < .01). Of the 14 patients adhering to short-course EA, 2 experienced a balancing measure of recurrent fever requiring resumption of EA, but no infection was identified. There were no BSIs, ICU admissions, or deaths during the hospitalization period in patients who received short-course EA. In this single-center QI project, short-course EA for initial fever was successfully applied to children undergoing allogeneic HCT using strict criteria and led to a significant decrease in broad-spectrum antibiotic use during hospitalization. These results should be validated in a prospective clinical trial to include the impact of short-course EA on antibiotic-resistant organisms, the intestinal microbiome, and HCT outcomes.

Distinguishing Incomplete Kawasaki and Nonsevere Multisystem Inflammatory Syndrome in Children.

OBJECTIVES: Characterizing inflammatory syndromes during the coronavirus disease 2019 pandemic was complicated by recognition of multisystem inflammatory syndrome in children (MIS-C), contemporaneous with episodes of Kawasaki disease. We hypothesized a substantial overlap between the 2 and assessed the performance of an MIS-C likelihood score in differentiating inpatients with nonsevere MIS-C from prepandemic incomplete Kawasaki disease (iKD) without coronary involvement. METHODS: A retrospective review of inpatient records was conducted; the nonsevere MIS-C cohort (March 2020-February 2021) met the 2023 definition for MIS-C; the iKD cohort (January 2018-January 2019) met the American Heart Association criteria for iKD without coronary involvement. We applied the likelihood score to both cohorts. We estimated the percent of children with iKD who could have met the clinical criteria of the MIS-C, had they presented in 2023. RESULTS: The 68 children in the nonsevere MIS-C cohort were older (8 vs 4 years, P < .001) than the 28 children in the iKD cohort. Those in the nonsevere MIS-C cohort had higher rates of thrombocytopenia (P < .001) and lymphopenia (P = .021); those in the iKD cohort had higher rates of pyuria (P < .001). Twenty-four (86%) children in the iKD cohort met the 2023 MIS-C definition. The scoring system correctly predicted 71% to 74% children with their respective clinical diagnoses. CONCLUSIONS: Though there was considerable clinical overlap, thrombocytopenia, lymphopenia, and the absence of pyuria were the most helpful parameters to distinguish children with nonsevere MIS-C from those with iKD.

Cardiac complications in children with acute COVID-19 vs multisystem inflammatory syndrome in children (MIS-C).

BACKGROUND: Cardiac involvement can lead to significant morbidity in children with acute COVID-19 or multisystem inflammatory syndrome in children (MIS-C). However, the presentation and outcomes of cardiac involvement may differ among these 2 conditions. We aimed to compare the frequency and extent of cardiac involvement among children admitted with acute COVID-19 vs those with MIS-C. METHODS: We conducted a cross sectional study of patients admitted to our hospital from March 2020 to August 2021 with symptomatic acute COVID-19 or MIS-C. Cardiac involvement was defined by presence of 1 or more of the following: elevated troponin, elevated brain natriuretic peptide, reduced left ventricular ejection fraction on echocardiogram, coronary dilation on echocardiogram, or abnormal electrocardiogram reading. RESULTS: Among 346 acute COVID-19 patients with median age of 8.9 years and 304 MIS-C patients with median age of 9.1 years, cardiac involvement was present in 33 acute COVID-19 patients (9.5%) and 253 MIS-C patients (83.2%). The most common cardiac abnormality was abnormal electrocardiogram in acute COVID-19 patients (7.5%) and elevated troponin in MIS-C patients (67.8%). Among acute COVID-19 patients, obesity was significantly associated with cardiac involvement. Among MIS-C patients, non-Hispanic Black race/ethnicity was significantly associated with cardiac involvement. CONCLUSIONS: Cardiac involvement is much more common in children with MIS-C than in those with acute COVID-19. These results reinforce our standardized practice of performing full cardiac evaluations and follow-up in all patients with MIS-C but only in acute COVID-19 patients with signs or symptoms of cardiac involvement.

Six-month cardiac outcomes in children with multisystem inflammatory syndrome in children.

BACKGROUND: Multisystem inflammatory syndrome in children is a rare, post-infectious complication of SARS-CoV-2 infection in children. We aimed to assess the long-term sequelae, particularly cardiac, in a large, diverse population. METHODS: We performed a retrospective cohort study of all children (aged 0-20 years, n = 304) admitted to a tertiary care centre with a diagnosis of multisystem inflammatory syndrome in children from March 1, 2020 to August 31, 2021 and had at least one follow-up visit through December 31, 2021. Data were collected at hospitalisation, 2 weeks, 6 weeks, 3 months, and 1 year after diagnosis, where applicable. Cardiovascular outcomes included left ventricular ejection fraction, presence or absence of pericardial effusion, coronary artery abnormalities, and abnormal electrocardiogram findings. RESULTS: Population was median age 9 years (IQR 5-12), 62.2% male, 61.8% African American (AA), and 15.8% Hispanic. Hospitalisation findings included abnormal echocardiogram 57.2%, mean worst recorded left ventricular ejection fraction 52.4% ± 12.4%, non-trivial pericardial effusion 13.4%, coronary artery abnormalities 10.6%, and abnormal ECG 19.6%. During follow-up, abnormal echocardiogram significantly decreased to 6.0% at 2 weeks and 4.7% at 6 weeks. Mean left ventricular ejection fraction significantly increased to 65.4% ± 5.6% at 2 weeks and stabilised. Pericardial effusion significantly decreased to 3.2% at 2 weeks and stabilised. Coronary artery abnormalities significantly decreased to 2.0% and abnormal electrocardiograms significantly decreased to 6.4% at 2 weeks and stabilised. CONCLUSION: Children with multisystem inflammatory syndrome in children have significant echocardiographic abnormalities during the acute presentation, but these findings typically improve within weeks. However, a small subset of patients may have persistent coronary abnormalities.

Infectious events in pediatric patients with acute lymphoblastic leukemia/lymphoma undergoing evaluation for fever without severe neutropenia.

BACKGROUND: Infections cause significant treatment-related morbidity during pediatric acute lymphoblastic leukemia/lymphoma (ALL/LLy) therapy. Fevers during periods without severe neutropenia are common, but etiologies are not well-described. This study sought to describe the bloodstream infection (BSI) and non-BSI risk in children undergoing therapy for ALL/LLy. METHODS: Demographic and clinical data were abstracted for febrile episodes without severe neutropenia at two children's hospitals. Treatment courses were stratified by intensity. Multivariate logistic regression evaluated characteristics associated with infection. RESULTS: There were 1591 febrile episodes experienced by 524 patients. Of these, 536 (34%) episodes had ≥1 infection; BSI occurred in 30 (1.9%) episodes. No BSIs occurred in episodes with a recent procedural sedation or cytarabine exposure. Presence of hypotension, chills/rigors, higher temperature, and infant phenotype were independently associated with BSI (p < .05). Of the 572 non-BSIs, the most common was upper respiratory infection (URI) (n = 381, 67%). Compared to episodes without infection, URI symptoms, higher temperature, absolute neutrophil count 500-999/µl, and evaluation during a low-intensity treatment course were more likely to be associated with a non-BSI (p < .05) and inpatient status was less likely to be associated with a non-BSI (p < .05). CONCLUSIONS: The BSI rate in pediatric patients with ALL/LLy and fever without severe neutropenia is low, but one-third of the time, patients have a non-BSI. Future research should test if the need for empiric antibiotics can be tailored based on the associations identified in this study.

Optimizing Antibiotic Treatment of Skin Infections in Pediatric Emergency and Urgent Care Centers.

OBJECTIVES: The objective was to optimize antibiotic choice and duration for uncomplicated skin/soft tissue infections (SSTIs) discharged from pediatric emergency departments (EDs) and urgent cares (UCs). METHODS: Pediatric patients aged 0 to 18 years discharged from 3 pediatric EDs and 8 UCs with a diagnosis of uncomplicated SSTIs were included. Optimal treatment was defined as 5 days of cephalexin for nonpurulent SSTIs and 7 days of clindamycin or trimethoprim/sulfamethoxazole for purulent SSTIs. Exclusion criteria included erysipelas, folliculitis, felon, impetigo, lymphangitis, paronychia, perianal abscess, phlegmon, preseptal or orbital cellulitis, and cephalosporin allergy. Baseline data were collected from January 2018 to June 2019. Quality improvement (QI) interventions began July 2019 with a revised SSTI guideline, discharge order set, and maintenance of certification (MOC) QI project. MOC participants received 3 education sessions, monthly group feedback, and individual scorecards. Balancing measures included return visits within 10 days requiring escalation of care. Data were monitored through March 2021. RESULTS: In total, 9306 SSTIs were included. The MOC QI project included 50 ED and UC physicians (27% of eligible physicians). For purulent SSTI, optimal antibiotic choice, plus duration, increased from a baseline median of 28% to 64%. For nonpurulent SSTI, optimal antibiotic choice, plus duration, increased from a median of 2% to 43%. MOC participants had greater improvement than non-MOC providers (P < .010). Return visits did not significantly change pre- to postintervention, remaining <2%. CONCLUSIONS: We improved optimal choice and reduced duration of antibiotic treatment of outpatient SSTIs. MOC participation was associated with greater improvement and was sustained after the intervention period.

Epidemiological and Clinical Features of Kawasaki Disease During the COVID-19 Pandemic in the United States.

Importance: Public health measures implemented during the COVID-19 pandemic had widespread effects on population behaviors, transmission of infectious diseases, and exposures to environmental pollutants. This provided an opportunity to study how these factors potentially influenced the incidence of Kawasaki disease (KD), a self-limited pediatric vasculitis of unknown etiology. Objectives: To examine the change in KD incidence across the United States and evaluate whether public health measures affected the prevalence of KD. Design, Setting, and Participants: This multicenter cohort study included consecutive, unselected patients with KD who were diagnosed between January 1, 2018, and December 31, 2020 (multicenter cohort with 28 pediatric centers), and a detailed analysis of patients with KD who were diagnosed between January 1, 2002, and November 15, 2021 (Rady Children's Hospital San Diego [RCHSD]). Main Outcomes and Measures: For the multicenter cohort, the date of fever onset for each patient with KD was collected. For RCHSD, detailed demographic and clinical data as well as publicly available, anonymized mobile phone data and median household income by census block group were collected. The study hypothesis was that public health measures undertaken during the pandemic would reduce exposure to the airborne trigger(s) of KD and that communities with high shelter-in-place compliance would experience the greatest decrease in KD incidence. Results: A total of 2461 KD cases were included in the multicenter study (2018: 894; 2019: 905; 2020: 646), and 1461 cases (median [IQR] age, 2.8 years [1.4-4.9 years]; 900 [61.6%] males; 220 [15.1%] Asian, 512 [35.0%] Hispanic, and 338 [23.1%] White children) from RCHSD between 2002 and 2021 were also included. The 28.2% decline in KD cases nationally during 2020 (646 cases) compared with 2018 (894 cases) and 2019 (905 cases) was uneven across the United States. For RCHSD, there was a disproportionate decline in KD cases in 2020 to 2021 compared with the mean (SD) number of cases in earlier years for children aged 1 to 5 years (22 vs 44.9 [9.9]; P = .02), male children (21 vs 47.6 [10.0]; P = .01), and Asian children (4 vs 11.8 [4.4]; P = .046). Mobility data did not suggest that shelter-in-place measures were associated with the number of KD cases. Clinical features including strawberry tongue, enlarged cervical lymph node, and subacute periungual desquamation were decreased during 2020 compared with the baseline period (strawberry tongue: 39% vs 63%; P = .04; enlarged lymph node: 21% vs 32%; P = .09; periungual desquamation: 47% vs 58%; P = .16). School closures, masking mandates, decreased ambient pollution, and decreased circulation of respiratory viruses all overlapped to different extents with the period of decreased KD cases. KD in San Diego rebounded in the spring of 2021, coincident with lifting of mask mandates. Conclusions and Relevance: In this study of epidemiological and clinical features of KD during the COVID-19 pandemic in the United States, KD cases fell and remained low during the period of masking and school closure. Mobility data indicated that differential intensity of sheltering in place was not associated with KD incidence. These findings suggest that social behavior is associated with exposure to the agent(s) that trigger KD and are consistent with a respiratory portal of entry for the agent(s).

Automated Identification of Immunocompromised Status in Critically Ill Children.

BACKGROUND: Easy identification of immunocompromised hosts (ICHs) would allow for stratification of culture results based on host type. METHODS: We utilized antimicrobial stewardship program (ASP) team notes written during handshake stewardship rounds in the pediatric intensive care unit (PICU) as the gold standard for host status; clinical notes from the primary team, medication orders during the encounter, problem list, and billing diagnoses documented prior to the ASP documentation were extracted to develop models that predict host status. We calculated performance for three models based on diagnoses/medications, with and without natural language processing from clinical notes. The susceptibility of pathogens causing bacteremia to commonly used empiric antibiotic regimens was then stratified by host status. RESULTS: We identified 844 antimicrobial episodes from 666 unique patients; 160 (18.9%) were identified as ICHs. We randomly selected 675 initiations (80%) for model training and 169 initiations (20%) for testing. A rule-based model using diagnoses and medications alone yielded a sensitivity of 0.87 (08.6-0.88), specificity of 0.93 (0.92-0.93), and positive predictive value (PPV) of 0.74 (0.73-0.75). Adding clinical notes into XGBoost model led to improved specificity of 0.98 (0.98-0.98) and PPV of 0.9 (0.88-0.91), but with decreased sensitivity 0.77 (0.76-0.79). There were 77 bacteremia episodes during the study period identified and a host-specific visualization was created. CONCLUSIONS: An electronic health record-based phenotype based on notes, diagnoses, and medications identifies ICH in the PICU with high specificity.

Serologic and Cytokine Signatures in Children With Multisystem Inflammatory Syndrome and Coronavirus Disease 2019.

BACKGROUND: The serologic and cytokine responses of children hospitalized with multisystem inflammatory syndrome (MIS-C) vs coronavirus disease 2019 (COVID-19) are poorly understood. METHODS: We performed a prospective, multicenter, cross-sectional study of hospitalized children who met the Centers for Disease Control and Prevention case definition for MIS-C (n = 118), acute COVID-19 (n = 88), or contemporaneous healthy controls (n = 24). We measured severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike receptor-binding domain (RBD) immunoglobulin G (IgG) titers and cytokine concentrations in patients and performed multivariable analysis to determine cytokine signatures associated with MIS-C. We also measured nucleocapsid IgG and convalescent RBD IgG in subsets of patients. RESULTS: Children with MIS-C had significantly higher SARS-CoV-2 RBD IgG than children with acute COVID-19 (median, 2783 vs 146; P < .001), and titers correlated with nucleocapsid IgG. For patients with MIS-C, RBD IgG titers declined in convalescence (median, 2783 vs 1135; P = .010) in contrast to patients with COVID-19 (median, 146 vs 4795; P < .001). MIS-C was characterized by transient acute proinflammatory hypercytokinemia, including elevated levels of interleukin (IL) 6, IL-10, IL-17A, and interferon gamma (IFN-γ). Elevation of at least 3 of these cytokines was associated with significantly increased prevalence of prolonged hospitalization ≥8 days (prevalence ratio, 3.29 [95% CI, 1.17-9.23]). CONCLUSIONS: MIS-C was associated with high titers of SARS-CoV-2 RBD IgG antibodies and acute hypercytokinemia with IL-6, IL-10, IL-17A, and IFN-γ.

Distinguishing immune activation and inflammatory signatures of multisystem inflammatory syndrome in children (MIS-C) versus hemophagocytic lymphohistiocytosis (HLH).

BACKGROUND: Multisystem inflammatory syndrome in children (MIS-C) is a potentially life-threatening sequela of severe acute respiratory syndrome coronavirus 2 infection characterized by hyperinflammation and multiorgan dysfunction. Although hyperinflammation is a prominent manifestation of MIS-C, there is limited understanding of how the inflammatory state of MIS-C differs from that of well-characterized hyperinflammatory syndromes such as hemophagocytic lymphohistiocytosis (HLH). OBJECTIVES: We sought to compare the qualitative and quantitative inflammatory profile differences between patients with MIS-C, coronavirus disease 2019, and HLH. METHODS: Clinical data abstraction from patient charts, T-cell immunophenotyping, and multiplex cytokine and chemokine profiling were performed for patients with MIS-C, patients with coronavirus disease 2019, and patients with HLH. RESULTS: We found that both patients with MIS-C and patients with HLH showed robust T-cell activation, markers of senescence, and exhaustion along with elevated TH1 and proinflammatory cytokines such as IFN-γ, C-X-C motif chemokine ligand 9, and C-X-C motif chemokine ligand 10. In comparison, the amplitude of T-cell activation and the levels of cytokines/chemokines were higher in patients with HLH when compared with patients with MIS-C. Distinguishing inflammatory features of MIS-C included elevation in TH2 inflammatory cytokines such as IL-4 and IL-13 and cytokine mediators of angiogenesis, vascular injury, and tissue repair such as vascular endothelial growth factor A and platelet-derived growth factor. Immune activation and hypercytokinemia in MIS-C resolved at follow-up. In addition, when these immune parameters were correlated with clinical parameters, CD8+ T-cell activation correlated with cardiac dysfunction parameters such as B-type natriuretic peptide and troponin and inversely correlated with platelet count. CONCLUSIONS: Overall, this study characterizes unique and overlapping immunologic features that help to define the hyperinflammation associated with MIS-C versus HLH.

Short-term Outcomes of Corticosteroid Monotherapy in Multisystem Inflammatory Syndrome in Children.

Importance: Optimal agents and duration of primary treatment for multisystem inflammatory syndrome in children (MIS-C) remain unclear. Objective: To compare short-term patient outcomes based on initial treatment with corticosteroids, intravenous immunoglobulin (IVIG), or both. Design, Setting, and Participants: This retrospective cohort study included patients in a tertiary-care pediatric hospital system who had MIS-C per the Centers for Disease Control and Prevention case definition during the period March 2020 to February 2021. Exposures: Immunomodulatory therapy within the first 24 hours (patients in the intensive care unit [ICU]) or 48 hours (non-ICU patients): corticosteroids alone, IVIG alone, and IVIG plus corticosteroids. Main Outcomes and Measures: Primary outcome was failure of initial therapy, defined as therapy escalation due to fever or worsening or lack of improvement of laboratory, cardiac, or noncardiac clinical factors after 24 hours (ICU patients) or 48 hours (non-ICU patients) from time of therapy initiation, per clinician assessment. Secondary outcomes included presence of complications, cardiovascular outcomes, fever duration, length of hospital and ICU stays, corticosteroid use duration, and need for readmission. Results: Among 228 eligible patients, 215 patients were included in the univariate analysis; median age was 8 years, and 135 (62.8%) were boys. There were 69 patients in the corticosteroids group, 31 patients in the IVIG group, and 115 patients in the IVIG plus corticosteroids group. Patients in the corticosteroids group had milder disease at presentation. After propensity score weighting including 179 patients (68 in the corticosteroids group and 111 in the IVIG plus corticosteroids group), rates of initial treatment failure were similar between groups. Among patients whose initial treatment failed, treatment failure in the IVIG plus corticosteroids group was more likely to be based on laboratory parameters (odds ratio [OR], 1.96; 95% CI, 1.07-3.60) and less likely to be based on cardiovascular markers (OR, 0.39; 95% CI, 0.2-0.76), per clinician assessment. Patients in the IVIG plus corticosteroids group had a longer median inpatient stay (6 vs 5 days; P = .001) and longer median corticosteroid course duration (10 vs 5 days; P = .04) compared with the corticosteroids group. Forty-nine patients (71% of 69 in the corticosteroids group) recovered after receiving corticosteroid monotherapy for 10 days or less. Conclusions and Relevance: Corticosteroid monotherapy is a reasonable management option for a subset of patients with MIS-C, particularly those with mild disease.