Multicenter Insights into Pediatric Extreme Leukocytosis: A 5-Year Retrospective Study

This study compared the clinical outcomes of pediatric emergency department (PED) patients with extreme leukocytosis (EL; WBC >25,000/µL) to those with moderate leukocytosis (ML; WBC 15,000 to 25,000/µL).

We conducted a retrospective analysis using the MALRADI database, which includes pediatric visits to Jerusalem's 3 major hospitals, the largest urgent care network, TEREM. Demographics, clinical data, lab results, and outcomes were analyzed for culture positivity and WBC trends over time.

Among 125,471 pediatric records, 19,955 (15.9%) had EL and 105,516 (84.1%) had ML. EL patients were younger (mean age 3.4 vs. 4.2 y, P <0.00001), had higher inflammatory markers (CRP 12.1 vs. 7.8 mg/L; ESR 46.6 vs. 34.6 mm/h; P <0.0001), and more frequently positive cultures (3% vs. 1.5%; P <0.0001). A rapid decline in WBC count within 24 hours was observed in EL patients, compared with a slight increase in the ML group. Malignancy was rare (0.06%) in EL cases, indicating that EL is generally infection-related in this population.

Extreme leukocytosis in pediatric patients is more frequently associated with infections requiring targeted monitoring but rarely indicates malignancy. These findings highlight the clinical importance of extreme leukocytosis and support the need for careful evaluation and monitoring in affected patients.