P2B058: Monocyte Anisocytosis Portends Severe Inflammatory/infectious Disease in Children

Background: Early determination of disease severity in an emergency setting is paramount for improving patient outcomes and healthcare costs. Monocyte anisocytosis, quantified as monocyte distribution width (MDW), has been shown to correspond with immune dysregulation in sepsis, severe COVID-19, and Multisystem Inflammatory Syndrome in Children. We hypothesize that MDW could broadly predict illness severity related to host-immune dysregulation in children.

Methods: We designed a retrospective study to analyze MDW from whole blood samples that were collected and analyzed on a UniCel DxH 900 analyzer (Beckman Coulter, Inc., Brea, CA) between 4/2020-9/2022. We enrolled children presenting to the ED, outpatient clinics, or admitted to the hospital of either Mass General for Children or Johns Hopkins Children’s Center. We also enrolled healthy children to serve as controls. Medical information was extracted from electronic medical records. Pediatric Sequential Organ Failure Assessment (pSOFA) scores were assigned to each patient. Outcomes were analyzed by t-test, and receiver operatory curve assessed accuracy of MDW in identifying disease severity.

Results: We analyzed samples from 435 children presenting with illness (mean age of 8 years, range 4 days to 18 years) and 216 healthy children (mean age of 12, range 1 to 18 years). MDW was significantly higher in children with illness requiring hospitalization (24.9 ± 6.7 mean and standard deviation) than in healthy controls (16 ± 1.7). Those admitted with fever showed an even greater increase in MDW (27.2 ± 6.4). Children with confirmed infection and a pediatric Sequential Organ Failure Assessment (pSOFA) score >1 (signifying signs of end-organ involvement) had MDW of 28.4 ± 6.9. A receiver operating curve comparing infected children with a pSOFA of 0 with a pSOFA >1 displayed an area under the curve of 73, suggesting MDW alone may serve as a useful tool in identifying children with severe disease.

Conclusion: MDW may be a useful biomarker to help clinicians quickly identify children presenting to the ED with signs of infection who are at high risk for severe illness and require closer monitoring or aggressive treatment.