Predictive factors associated with mortality outcomes of severe COVID-19 pneumonia in elderly patients, Suratthani Hospital, Thailand

Abstract

Background: The first wave of the COVID-19 outbreak in Thailand started in March 2020, and thirteen months later, the third wave started in April 2021 and became the delta variant after May 2021. The Delta variant is more contagious and causes more severe illness than the previous variants due to the lack of strict social distancing policies and public health intervention. The Thai CDC guideline published in April 2021 categorized patients under investigation criteria who underwent real-time reverse transcriptase polymerase chain reaction (RT-PCR) for SAR-CoV2. However, the significant increase in the number of patients and more severe disease in the third outbreak overwhelmed the hospital’s  capacity. Elderly patients with more chronic diseases are susceptible to COVID-19 pneumonia. This resulted in unfavorable outcomes and fatality.

Objective: The primary outcome was to identify factors associated with the 28-day mortality outcome of severe COVID-19 pneumonia in elderly patients. The secondary outcome aimed to explore potential predictors and develop a prediction model to prognosticate mortality for severe COVID-19 pneumonia patients.

Methods: This retrospective cohort study included hospitalized COVID-19 pneumonia patients during April 2021-January 2022 at Suratthani hospital. The patients were divided into 2 groups based on the 28-day mortality outcome.

Results: Of the 376 elderly patients with severe COVID-19 pneumonia, 85 (22.61%) eventually died within 28 days, and the median time from hospital admission to death was 35 days. The mortality rate of COVID-19 was 16 per 1,000 person-days. Most of the patients were female (53.46%), with a mean age of 75 years. The two most common comorbidities were hypertension (68.88%) and diabetes mellitus (44.41%). The mean duration between the symptom onset and the admission date was longer in the death group compared with the survival group (4.57 vs. 3.82 days). Intensive Care Unit (ICU) admission was observed in 149 (39.63%) of the patients. The mean ventilator duration (8.00 vs. 15.67 days) and the length of hospital stay (10.99 vs. 13.93 days) were shorter in the death group compared with the survival group due to more severe cases among the deaths. Most patients in the survival group were started with favipiravir 243 (83.51%), but only received remdesivir 47 (16.15%). Adjuvant treatment with corticosteroids was used 69 cases (81.18%) in the deceased group compared to 218 (74.91%) in the survival group.

         Among the patients, 101 (26.86%) had received only one dose of the COVID-19 vaccine. 52 (13.83%) had received two doses of the COVID-19 vaccine. A multivariate analysis revealed significantly three factors that were associated with 28-day mortality [odd ratio (95% CI); p-value]: ICU admission [4.19 (1.92, 9.15); p <0.001], invasive mechanical ventilator [3.76 (1.33, 10.64); p = 0.013], serum creatinine greater than 2 mg/dl [3.68 (1.35, 10.02); p = 0.011]. The prediction equation for 28 day mortality is: (ICU admission*2) + (ventilator support*1) + (serum creatinine >2mg/dl *1). The AUROC was 0.82.

Conclusions: In conclusion, the mortality rate in our study was 22.61%. We identified some factors, such as the patients who had serum creatinine greater than 2 mg/dl, respiratory failure, required ventilator support, and needed intensive care support related to the high mortality among severe COVID-19 pneumonia in elderly patients. We propose a prediction model for the 28-day mortality in severe COVID-19 pneumonia, which had good performance.