Shock index predicted mortality in geriatric patients with influenza in the emergency department

The shock index is a rapid and simple tool used to predict mortality in patients with acute illnesses including sepsis, multiple trauma, and postpartum hemorrhage. However, its ability to predict mortality in geriatric patients with influenza in the emergency department (ED) remains unclear. This study was conducted to clarify this issue.

We conducted a retrospective case-control study, recruiting geriatric patients (≥ 65 years) with influenza visiting the ED of a medical center between January 01, 2010 and December 31, 2015. Demographic data, vital signs, shock index, past histories, subtypes of influenza, and outcomes were included for the analysis. We investigated the association between shock index ≥1 and 30-day mortality.

In total, 409 geriatric ED patients with mean age of 79.5 years and nearly equal sex ratio were recruited. The mean shock index ± standard deviation was 0.7 ± 0.22 and shock index ≥1 was accounted for in 7.1% of the total patients. Logistic regression showed that shock index ≥1 predicted mortality (odds ratio: 6.80; 95% confidence interval: 2.39-19.39). The area under the receiver operating characteristic was 0.62 and the result of the Hosmer-Lemeshow goodness-of-fit test was 0.23. The sensitivity, specificity, positive predictive value, and negative predictive value of a shock index ≥1 were 30.0%, 94.1%, 20.0%, and 96.4%.

A shock index ≥1 has a high specificity, negative predictive value, and good reliability to predict 30-day mortality in geriatric ED patients with influenza.