<![CDATA[Pneumonia is an acute infection of the lung parenchyma that commonly affects children under five years of age and remains a leading cause of pediatric morbidity and mortality worldwide. The inflammatory response to pneumonia is accompanied by alterations in hematological parameters, including leukocytosis and lymphopenia, which may reflect disease severity. This study aimed to evaluate the association between leukocyte and lymphocyte counts and clinical outcomes in toddlers hospitalized with pneumonia at Budhi Asih Regional Hospital. This observational analytical study employed a cross-sectional design using medical records of 117 toddlers diagnosed with pneumonia. Leukocytosis was defined as a leukocyte count of >15,500 cells/µL, while lymphopenia was defined as a lymphocyte count of <2,000 cells/µL. Clinical outcomes were categorized as improvement or deterioration. Associations between hematological parameters and clinical outcomes were analyzed using the Chi-square test, and effect sizes were expressed as odds ratios (ORs) with 95% confidence intervals (CIs). Leukocytosis was significantly associated with clinical deterioration (OR = 24.27, 95% CI: 6.97–84.52; p < 0.001). Likewise, lymphopenia was significantly associated with unfavorable clinical outcomes (OR = 3.05, 95% CI: 1.13–8.26; p = 0.024). A significant association was also observed between leukocyte and lymphocyte abnormalities (p = 0.004). Children with leukocytosis and lymphopenia were more likely to experience clinical deterioration than those without these hematological abnormalities. These findings suggest that leukocytosis and lymphopenia are significantly associated with clinical outcomes in toddlers with pneumonia and may serve as useful adjunctive laboratory markers in clinical assessment. However, because of the cross-sectional design, causal or prognostic inferences cannot be established. Prospective longitudinal studies are warranted to validate their predictive value for disease progression and clinical outcomes. Keywords: Clinical outcomes, leukocytes, lymphocytes, toddler pneumonia ]]>
