The predictive ability of blood-based biomarkers to detect bacteremia in hospitalized neonatal foals.

Overview

• This study investigates the effectiveness of certain blood-based biomarkers, including neutrophil-to-lymphocyte ratio (NLR) and plasma cell-free DNA (cfDNA), to predict bacteremia in hospitalized neonatal foals.
• The research evaluates whether these markers combined with standard clinical and hematological parameters can identify bacteremia and distinguish between types of bacterial infections early in foals less than 5 days old.

Background and Importance

• Septicemia (bacteremia) in neonatal foals is a serious, life-threatening condition where bacteria are present in the blood.
• Early and accurate detection improves treatment outcomes and survival rates.
• In human medicine, blood ratios like neutrophil-to-lymphocyte ratio (NLR), neutrophil-to-monocyte ratio (NMR), monocyte-to-lymphocyte ratio (MLR), and cell-free DNA (cfDNA) are useful for early detection of blood infections.
• There was limited information on how well these biomarkers perform in neonatal foals, necessitating this research.

Study Design and Methods

• The study included 391 foals less than 5 days old, hospitalized with suspected infection.
• Each foal had a blood culture taken aseptically at admission to determine presence and type of bacteremia (Gram-positive, Gram-negative, or polymicrobial).
• Blood samples were analyzed for:
  • Complete blood count (CBC) parameters including white blood cell count (WBC), neutrophils, lymphocytes, monocytes
  • Immunoglobulin G (IgG) levels
  • Ratios such as NLR, NMR, MLR
  • Plasma cell-free DNA (cfDNA) measured using fluorometry
• Physical examination findings and hematologic parameters were incorporated into logistic regression models to predict bacteremia.
• The area under the curve (AUC) metric from receiver operating characteristic (ROC) analysis was used to evaluate model predictive performance.

Key Findings

• Independent predictors of bacteremia included:
  • Plasma cfDNA levels
  • Immunoglobulin G (IgG)
  • Neutrophil-to-lymphocyte ratio (NLR)
  • White blood cell count (WBC)
• A combined model using these variables demonstrated excellent ability to discriminate foals with positive blood cultures (AUC = 0.806).
• For Gram-negative bacteremia specifically:
  • Plasma cfDNA, IgG, and neutrophil counts were independent predictors.
  • The composite model showed excellent discrimination (AUC = 0.807).
• For Gram-positive bacteremia:
  • Monocyte count and age were predictors.
  • The model showed fair discriminatory ability (AUC = 0.67).
• The NMR and MLR ratios did not significantly differ between bacteremic and non-bacteremic groups, indicating they are not reliable markers in this context.

Implications and Conclusions

• The study supports the use of NLR and plasma cfDNA as valuable blood-based biomarkers in detecting bacteremia in neonatal foals early.
• Combining these markers with standard hematologic and clinical parameters improves the accuracy of diagnosis on admission.
• Improved early identification can lead to timely medical intervention and potentially better survival outcomes.
• The research suggests that the inflammatory response and cellular injury reflected by cfDNA and blood cell ratios are significantly altered in bacteremic foals.
• Future clinical protocols might incorporate these biomarkers for rapid screening and management of neonatal foals suspected of septicemia.