Diagnostic utility of serum ferritin in culture proven bacterial infection: an observational study

Diagnosing neonatal sepsis remains challenging due to the low yield of blood cultures. Most neonatal intensive care units (NICUs) rely on a sepsis screen for diagnosis. This study aimed to evaluate the diagnostic utility of serum ferritin as a standalone marker and in combination with the existing septic screen. This prospective study was conducted between August 2023 and January 2024 in a level-III NICU and included 160 neonates with suspected sepsis who stayed in the NICU for more than 48 h. Sensitivity, specificity, and the area under the receiver operator curve (ROC) for serum ferritin were calculated in relation to culture-proven bacterial infection. The Youden Index was used to determine the optimal serum ferritin cut-off value. The mean age of the neonates was 1.83 ± 2.26 days; 64% were boys, 69% were term, and 54% had low birth weight. Among the outcomes, 28% had positive blood cultures, 45% were septic screen positive, and 27% had clinical sepsis. The mean serum ferritin level was significantly higher in septic screen-positive neonates (426.9 ng/mL) than in culture-positive cases (326.61 ng/mL; p < 0.001). In neonates with blood culture-positive sepsis, a serum ferritin cut-off value of > 295.5 ng/mL yielded an Area Under Curve (AUC) of 0.70, sensitivity of 54%, and specificity of 86% (Youden Index: 0.403). The sepsis screen alone had an AUC of 0.58, sensitivity of 57%, and specificity of 60%. When serum ferritin was added to the septic screen, the AUC remained similar (0.59), sensitivity increased to 72%, but specificity decreased to 46%. Serum ferritin levels were higher in septic screen-positive sepsis than in culture-positive sepsis. Adding serum ferritin (cut-off: >295 ng/mL) to the septic screen improved its sensitivity, albeit with reduced specificity. Serum ferritin has limited role adjunctive value, can have a role as a “rule - out” marker in diagnosing culture positive bacterial infection.