A novel evaluation indicator for pediatric fulminant myocarditis: diagnostic and prognostic value of the HALP score

Pediatric fulminant myocarditis (FM) is characterized by a critical and rapidly progressive course. Current diagnostic approaches primarily rely on cardiac function and myocardial injury markers, which fail to comprehensively assess the associated systemic inflammation and immune dysregulation. The hemoglobin, albumin, lymphocyte, and platelet (HALP) score, a composite index integrating hemoglobin (Hb), albumin (Alb), lymphocyte count (Lym), and platelet count (Plt), offers a new perspective for evaluating the severity of pediatric fulminant myocarditis. To evaluate the diagnostic and prognostic utility of the HALP score in pediatric patients with fulminant myocarditis. This retrospective study included 71 children with myocarditis (22 with FM, 49 with non-fulminant myocarditis NFM). The HALP score was calculated from admission laboratory parameters (Hb × Alb × Lym / Plt). Clinical manifestations, laboratory parameters, and echocardiographic findings were compared between groups. Diagnostic performance was assessed via receiver operating characteristic (ROC) curve analysis. Associations with clinical outcomes (Pediatric Intensive Care Unit PICU admission, mechanical ventilation, vasoactive drug use) were analyzed. Independent predictors of FM were identified using multivariate logistic regression. Patients in the FM group exhibited significantly higher rates of gallop rhythm (72.73% vs. 22.45%, P < 0.001), hepatomegaly (50.00% vs. 8.16%, P < 0.001) and dyspnea/tachypnea (31.82% vs. 12.24%, P = 0.049) compared to the NFM group. The median HALP score was significantly lower in the FM group compared to the NFM group (27.06 vs. 50.22, P = 0.005). The HALP score had an area under the ROC curve (AUC) of 0.724 for diagnosing FM, with an optimal cutoff of 36.07 (sensitivity 77.6%, specificity 68.2%). Based on this cutoff, children in the low-HALP group (< 36.07, n = 26) had significantly higher rates of mechanical ventilation (30.77% vs. 6.67%, P = 0.014), PICU admission (69.23% vs. 15.56%, P < 0.001), and vasoactive drug use (61.54% vs. 15.56%, P < 0.001) compared to the high-HALP group (≥ 36.07, n = 45). Multivariate analysis confirmed that a lower HALP score (OR = 0.946, 95% CI: 0.895–0.999, P = 0.047), along with elevated high-sensitivity troponin I (Hs-cTnI) (OR = 1.086, 95% CI: 1.019–1.158, P = 0.012) and reduced left ventricular ejection fraction (LVEF) (OR = 0.865, 95% CI: 0.783–0.956, P = 0.005), were independent risk factors for FM. The HALP score, a simple composite index derived from routine blood tests, demonstrates potential value for the diagnosis, severity stratification, and prognosis prediction of pediatric fulminant myocarditis. It complements conventional cardiac markers by reflecting systemic inflammation–immune status. Given the exploratory nature of this study, these findings warrant validation in larger prospective multicenter studies.