Association between variables measured in the ambulance and in-hospital mortality among adult patients with and without infection: a prospective cohort study.

BACKGROUND: Patients presenting with infection to the ambulance are common, but risk factors for poor outcome are not known. The primary aim of the current study was to study the association between variables measured in the ambulance and mortality among adult patients with and without infection. The secondary aim was to study the association between these variables and mortality in a subgroup of patients who developed sepsis within 36 h.

METHODS: Prospective cohort study of 553 ambulance patients with, and 318 patients without infection, performed in Stockholm during 2017-2018. The association between 21 variables (8 keywords related to medical history, 6 vital signs, 4 blood tests, and age, gender, comorbidity) and in-hospital mortality was analysed using logistic regression.

RESULTS: Among patients with infection, inability of the patient to answer questions relating to certain symptoms such as pain and gastrointestinal symptoms was significantly associated with mortality in univariable analysis, in addition to oxygen saturation < 94%, heart rate > 110 /min, Glasgow Coma Scale (GCS) < 15, soluble urokinase Plasminogen Activator Receptor (suPAR) 4.0-7.9 ng/mL, suPAR ≥ 8.0 ng/mL and a Charlson comorbidity score ≥ 5. suPAR ≥ 8.0 ng/mL remained significant in multivariable analysis (OR 25.4; 95% CI, 3.2-199.8). Among patients without infection, suPAR ≥ 8.0 ng/mL and a Charlson comorbidity score ≥ 5 were significantly associated with mortality in univariable analysis, while suPAR ≥ 8.0 ng/mL remained significant in multivariable analysis (OR 56.1; 95% CI, 4.5-700.0). Among patients who developed sepsis, inability to answer questions relating to pain remained significant in multivariable analysis (OR 13.2; 95% CI, 2.2-78.9), in addition to suPAR ≥ 8.0 ng/mL (OR 16.1; 95% CI, 2.0-128.6).

CONCLUSIONS: suPAR ≥ 8.0 ng/mL was associated with mortality in patients presenting to the ambulance both with and without infection and in those who developed sepsis. Furthermore, the inability of the ambulance patient with an infection to answer questions relating to specific symptoms was associated with a surprisingly high mortality. These results suggest that suPAR and medical history are valuable tools with which to identify patients at risk of poor outcome in the ambulance and could potentially signal the need of enhanced attention.

TRIAL REGISTRATION: ClinicalTrials.gov, NCT03249597. Registered 15 August 2017-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03249597 .