Neutrophil-to-Lymphocyte Ratio Calculation and Clinical Significance
Calculation
The N/L ratio is 16.4, calculated by dividing the neutrophil percentage (82%) by the lymphocyte percentage (5%).
- Simply divide: 82 ÷ 5 = 16.4 1, 2
- This can be done using either relative percentages (as above) or absolute counts 1, 2
Clinical Significance in This Patient
This markedly elevated N/L ratio of 16.4 indicates severe systemic inflammation or infection and correlates with a more severe clinical course. 1, 2
Interpretation of the N/L Ratio Value
- Normal N/L ratio range: 1-2 1
- Values >3.0 are pathological and indicate active infection, inflammation, or stress 1
- Values >11-17 indicate severe critical illness, sepsis, or major systemic stress 1
- This patient's ratio of 16.4 falls in the severe range, suggesting significant bacterial infection or sepsis 1, 2
What This Means for Your Patient
The combination of neutrophilia (82%), marked lymphopenia (5%), and symptoms of vomiting, diarrhea, and fever strongly suggests bacterial infection requiring immediate evaluation and likely empiric antibiotics. 3, 4
- The neutrophil percentage of 82% is elevated (normal ~40-70%) and indicates bacterial infection 3, 2
- The lymphocyte percentage of 5% represents severe lymphopenia (normal ~20-40%), which occurs with acute bacterial stress 2, 5
- Higher N/L ratios predict bacterial infection over viral infection 4
- Patients with septicemia have significantly higher N/L ratios compared to other bacterial infections 4
Prognostic Implications
Higher N/L ratios correlate with worse outcomes, including longer illness duration, increased mortality risk, and multi-organ damage. 5
- In patients with diarrhea and fever, higher neutrophil counts and lower lymphocyte counts are independent risk factors for in-hospital death 5
- Longer duration of diarrhea combined with neutrophilia and lymphopenia predicts longer illness course 5
- Dynamic monitoring of N/L ratio is essential—declining values below 7 indicate clinical improvement, while persistently elevated or rising values suggest worsening sepsis 1
Recommended Diagnostic Approach
Obtain blood cultures immediately, assess for specific infection sources (gastrointestinal given diarrhea/vomiting), and consider empiric antibiotics based on suspected source. 3, 4
- Blood cultures should be drawn if systemic infection is suspected 3
- Evaluate stool for pathogens including C. difficile given gastrointestinal symptoms 6
- Assess volume status and signs of peritonitis 3
- Consider imaging if abdominal source suspected 3
Common Pitfalls to Avoid
- Do not delay antibiotics while awaiting culture results in a patient with N/L ratio >11 and clinical signs of sepsis 1
- Do not assume viral etiology—high N/L ratios strongly favor bacterial infection 4
- Monitor N/L ratio serially (every 6-24 hours) to track response to treatment—failure to decline suggests inadequate source control or antibiotic coverage 1, 2