Exclusion of bacterial co-infection in COVID-19 using baseline inflammatory markers and their response to antibiotics
Claire Y Mason1, Tanmay Kanitkar1, Charlotte J Richardson1
1Department of Infection, Royal Free London NHS Trust, London, UK.
Background:
COVID-19 is infrequently complicated by bacterial co-infection, but antibiotic prescriptions are common. We used community-acquired pneumonia (CAP) as a benchmark to define the processes that occur in bacterial pulmonary infections, testing the hypothesis that baseline inflammatory markers and their response to antibiotic therapy could distinguish bacterial co-infection from COVID-19.
Methods:
Retrospective cohort study of CAP (lobar consolidation on chest radiograph) and COVID-19 (PCR detection of SARS-CoV-2) patients admitted to Royal Free Hospital (RFH) and Barnet Hospital (BH), serving as independent discovery and validation cohorts. All CAP and >90% COVID-19 patients received antibiotics on hospital admission.
Results:
We identified 106 CAP and 619 COVID-19 patients at RFH. Compared with COVID-19, CAP was characterized by elevated baseline white cell count (WCC) [median 12.48 (IQR 8.2-15.3) versus 6.78 (IQR 5.2-9.5) ×106 cells/mL, P < 0.0001], C-reactive protein (CRP) [median 133.5 (IQR 65-221) versus 86.0 (IQR 42-160) mg/L, P < 0.0001], and greater reduction in CRP 48-72 h into admission [median ΔCRP -33 (IQR -112 to +3.5) versus +14 (IQR -15.5 to +70.5) mg/L, P < 0.0001]. These observations were recapitulated in the independent validation cohort at BH (169 CAP and 181 COVID-19 patients). A multivariate logistic regression model incorporating WCC and ΔCRP discriminated CAP from COVID-19 with AUC 0.88 (95% CI 0.83-0.94). Baseline WCC >8.2 × 106 cells/mL or falling CRP identified 94% of CAP cases, and excluded bacterial co-infection in 46% of COVID-19 patients.
Conclusions:
We propose that in COVID-19, absence of both elevated baseline WCC and antibiotic-related decrease in CRP can exclude bacterial co-infection and facilitate antibiotic stewardship efforts.
Insights
This study found that elevated white cell count (WCC) and decreasing C-reactive protein (CRP) levels can help distinguish bacterial pneumonia from COVID-19. This distinction aids in appropriate antibiotic use, improving antibiotic stewardship in COVID-19 patients.
Area of Science:
- Infectious Diseases
- Pulmonology
- Critical Care Medicine
Background:
- Bacterial co-infections are uncommon in COVID-19, yet antibiotics are frequently prescribed.
- Community-acquired pneumonia (CAP) serves as a benchmark for bacterial pulmonary infections.
- Inflammatory markers and their response to antibiotics may differentiate bacterial co-infection from COVID-19.
Purpose of the Study:
- To test if baseline inflammatory markers and their response to antibiotics can distinguish bacterial co-infection from COVID-19.
- To evaluate the utility of white cell count (WCC) and C-reactive protein (CRP) changes in differentiating these conditions.
- To support antibiotic stewardship by identifying COVID-19 patients unlikely to have bacterial co-infection.
Main Methods:
- Retrospective cohort study comparing CAP and COVID-19 patients.
- Utilized discovery (RFH) and validation (BH) cohorts.
- Analyzed baseline WCC, CRP, and CRP change (ΔCRP) 48-72 hours post-admission.
Main Results:
- CAP patients exhibited significantly higher baseline WCC and CRP compared to COVID-19 patients.
- CAP patients showed a greater reduction in CRP after 48-72 hours compared to COVID-19 patients.
- A multivariate model using WCC and ΔCRP achieved an AUC of 0.88 for discriminating CAP from COVID-19.
Conclusions:
- Absence of elevated baseline WCC and antibiotic-associated CRP decrease can exclude bacterial co-infection in COVID-19.
- These findings support antibiotic stewardship efforts by enabling more judicious antibiotic prescribing.
- The study proposes a method to identify COVID-19 patients who do not require antibiotics for bacterial co-infection.
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