(O-B7) Comparing the Prognostic Value of Lactate to the Neutrophil to Lymphocyte Ratio Among Sepsis Patients: A Prospective Cohort Study

Objectives: The objective of this study was to compare the prognostic value of the neutrophil to lymphocyte ratio (NLR) to lactate with regard to in-hospital mortality among septic patients and different septic patient subgroups.

Background: The role of the neutrophil-to-lymphocyte ratio (NLR) was studied in conditions, such as appendicitis, cardiovascular disease, malignancy and sepsis. In sepsis, it was shown to be useful in predicting bacteremia, diagnosing sepsis, predicting mortality and monitoring response to therapy. Lactate is a widely used biomarker in diagnosing and risk stratifying patients with sepsis. However, a single serum lactate has its limitations; lactate levels can be elevated by several commonly used medications and in liver and kidney disease. Lactate can also be elevated in patients with hematologic malignancies with no apparent infection.

Methods: This was a prospective cohort study including adult septic or septic shock patients presenting to the Emergency Department of a tertiary care center , between September 2018 and February 2021. Sepsis was defined according to the sepsis-3 guidelines. Patients were divided into two groups: survivors and non-survivors. Stepwise logistic regression including all statistically and clinically significant variables was performed to find the best model that fits the data and that explains the association between mortality and all predictor variables. The prognostic value of both NLR and lactate was determined using receiver operating characteristic curves from which we obtained their AUCs.

Results: A total of 874 septic patients were included in this study. 22.77 % of the patients died during their hospital stay. The mean lactate level and NLR of the whole population was 2.95±2.27 mmol/L and 16.84±20.28. The NLR and lactate level were significantly higher in the non-survivor group (20.53±25.18 vs 15.77±18.52, p=0.02 and 3.79±3.45mmol/L vs 2.70±1.71mmol/L, p-value < 0.0001). The AUC value of the NLR ratio was 0.552 with a 95% CI=0.504-0.599, whereas that of lactate was 0.591 with a 95% CI=0.544-0.637. There was no significant difference in the AUC between both variables with a p-value=0.22. There was no statistically significant difference in the AUCs between lactate and NLR in patients with septic shock, Lactate < 2, Lactate≥2, diabetes, malignancy, chronic kidney diseases, other sources of infection, albumin ≥30 and age ≥ 65. However, lactate outperformed NLR in the following subgroups: albumin < 30 g/L, patients less than 65 years of age and patients with sepsis due to a urinary tract infection. In the stepwise logistic regression, NLR was not associated with in-hospital mortality (OR=1.003, 95% CI=0.994-1.012, p=0.544), whereas lactate was associated with hospital mortality (OR=1.188, 95% CI=1.086-1.299, p< 0.0001)

Conclusions: In this study, lactate but not NLR was associated with in-hospital mortality. There was no significant difference in the AUCs between lactate and NLR among sepsis patients and among the majority of the subgroups in this study (including septic shock patients). However, lactate outperformed NLR in the following subgroups: albumin < 30 g/L, patients less than 65 years of age and patients with sepsis due to a urinary tract infection. Our results advocate for the continued use of serum lactate rather than NLR, despite its limitations, as a predictor of mortality among septic patients and the different subgroups in this study.

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Funding (Optional): None