Older age, CXR findings, elevated CRP predict COVID-19 pneumonia, ICU admission, death

Elevated C-reactive protein (CRP), older age, and chest radiography (CXR) findings are predictive of COVID-19 pneumonia, admission to intensive care unit (ICU), and mortality, according to a Singapore study, adding that prospective studies should be undertaken to validate these findings.

“As expected, patients aged >50 years had a significantly higher proportion of pneumonia diagnosis as compared to those aged ≤50 years,” the researchers said. “Furthermore, a diagnosis of pneumonia was associated with ICU admission and/or death.”

This retrospective, single-centre cohort study included 294 confirmed COVID-19 patients admitted to a Singapore tertiary hospital. The predictive performance of emergency department (ED)-specific variables was analysed using multivariable logistic regression, and the accuracy of continuous variables were measured using area under receiver operating characteristic (ROC) curve.

Patients with pneumonia were usually older (mean age 52.0 years; p<0001) and had higher CRP (33.8 mg/L; p<0.001), while those with indeterminate CXR findings were more likely to develop pneumonia relative to normal findings (37.5 percent vs 4.3 percent; p<0.001). [Singapore Med J 2021;doi:10.11622/smedj.2021084]

Patients admitted to ICU were also older (mean age 60 years; p<0.001) and had higher CRP (40.0 mg/L; p<0.001). Moreover, a diagnosis of COVID-19 pneumonia appeared to significantly increase the likelihood of ICU admission and death (30.0 percent vs 0.39 percent; p<0.001).

In multivariable logistic regression analysis, age (adjusted odds ratio [aOR], 1.07, 95 percent confidence interval [CI], 1.0–1.16; p=0.049), CRP (aOR, 1.05, 1.02–1.10; p=0.006), and CXR findings (aOR, 50.00, 95 percent CI, 11.90–279.00; p<0.001) were significantly associated with pneumonia. ROC curve analysis revealed a CRP of 23.3 mg/L as the optimal cutoff for predicting pneumonia.

Similarly, the same variable positively correlated with ICU admission and death (age: aOR, 1.13, 95 percent CI, 1.03–1.27; p=0.02; CRP: aOR, 1.02, 95 percent CI, 1.00–1.04; p=0.044; CXR findings: aOR, 11.60, 95 percent CI, 1.33–144.00; p=0.031).

“These predictors concurred with those reported by other studies on COVID-19 disease progression,” the researchers said. “For patients without obvious pneumonia findings on initial CXR, our subgroup analysis found that CRP and age were robust predictors of pneumonia.” [BMJ 2020;369:m1966; Clin Microbiol Infect 2020;26:1400-1405; Ann Emerg Med 2020;76:394-404]

The use of chest computed tomography (CT) is not recommended by the American College of Radiology for screening or diagnosis of COVID-19. However, CXR is commonly performed for patients with suspected or diagnosed COVID-19 infection in EDs worldwide, including in Singapore. [https://www.acr.org/Advocacy-and-Economics/ACR-Position-Statements/Recommendations-forChest-Radiography-and-CT-for-Suspected-COVID19-Infection]

“As CT is not routinely performed in Singapore, it is important for emergency physicians to be able to identify CXR findings that are suggestive of pneumonia in the emergency setting in order to guide management, predict disease progression, and guide disposition,” the researchers said.

The current study was limited by its retrospective nature and small sample size. Its primary outcome measure (ie, presence or development of pneumonia during hospital admission) could also be perceived as a “subjective clinical judgment,” but this was allayed by a high inter-rater reliability in the outcome. Furthermore, incorporation bias was present since the initial CXR findings were part of the outcome.

“Lastly, the external validity of this study may be limited, as COVID-19 affected mainly the younger population and foreign workers in Singapore,” the researchers said.