Date of Award


Document Type


Degree Name

Master of Medicine (MMed)

First Supervisor/Advisor

Dr Daniel Maina

Second Supervisor/Advisor

Dr Geoffrey Omuse

Third Supervisor/Advisor

Dr Benjamin Wachira


Pathology (East Africa)


Background: Sepsis is a leading cause of death and now a global health priority. Rapid identification, diagnosis and intervention can result in reduced in-hospital mortality. Elevated lactate has been shown to be a strong predictor of in-hospital mortality. However, the optimal cut-off has not been well defined. Identification of the optimal Point-of-Care (POC) lactate cut off that best predicts in-hospital mortality can therefore be used to rapidly risk stratify patients with suspected sepsis and septic shock presenting to the emergency department allowing for immediate intervention.

Objective: To determine the lactate cutoff from an initial Point-of-Care lactate result from a GEM 3500® blood gas analyzer that best predicted in-hospital mortality in patients with suspected sepsis and septic shock presenting to the emergency department.

Methods: This was a cross-sectional study. All adult patients who presented to the emergency department between 1st January 2018 and 31st August 2020 with suspected sepsis or septic shock and were admitted to the hospital were included in the study. Initial POC lactate results, demographic and outcome data were collected. A receiver operating characteristic (ROC) curve for initial POC lactate values was be plotted to determine the area under the curve (AUC). An optimal initial lactate cut-off was then determined using the Youden Index. Kaplan-Meier curves were used to determine the hazard ratio for the identified lactate cut-off

Results: The final study cohort comprised of 123 patients with a median age of 61 years (interquartile range [IQR] 41.0-77.0). Initial lactate independently predicted in-hospital mortality (OR 1.41 95% CI [1.06, 1.87] p=0.018). An initial lactate cutoff of 3.5mmol/L was found to best predict in-hospital mortality, AUC 0.752 (95% CI, 0.643 to 0.86, sensitivity 66.7%, specificity 71.4%). Mortality was 42.1% (16/38) in patients with initial lactate of ≥ 3.5mmol/L and 12.7% (8/63) in patients with an initial lactate of less than 3.5mmol/L (HR, 3.388; 95% CI, 1.432–8.018; p<0.005).

Conclusion: An initial POC lactate of ≥ 3.5mmol/L best predicted in-hospital mortality in patients presenting with suspected sepsis and septic shock to the emergency department. This should be incorporated in sepsis and septic shock protocols to help in the early identification and management of these patients to reduce their in-hospital mortality.