NEWS & PERSPECTIVE
Local retrospective study finds lower risk of acute kidney injury in ICU patients with COVID-19 vs. seasonal influenza
Influenza and COVID-19 are the most common respiratory viral infections among intensive care unit (ICU) patients, which can result in multiple organ failures requiring intensive support.1 Acute kidney injury (AKI) is a frequent complication in critically ill patients with these infections.1 To investigate the incidence and disease patterns of AKI in patients with COVID-19 and influenza, researchers at the LKS Faculty of Medicine, the University of Hong Kong (HKUMed) conducted a retrospective cohort study using 10 years of data (2013-2023) from a territory-wide electronic health record system, focusing on ICU admissions for individuals aged ≤18 with positive polymerase chain reaction (PCR) results for SARS-CoV-2 or influenza A across 15 public hospitals in Hong Kong.1
AKI is a complication frequently observed in ICU patients with respiratory viral infections such as influenza and COVID-19.1 In patients with COVID-19, SARS-CoV-2 can cause AKI by directly infecting kidney podocytes and proximal tubular cells or dysregulating immune responses that lead to AKI.2 Similarly, the influenza A virus has been hypothesized to induce renal hypoperfusion, rhabdomyolysis and disseminated intravascular coagulation which contribute to acute tubular necrosis and glomerular microthrombosis.3 A previous study from the first wave of the COVID-19 pandemic based on a cohort of United States veterans had found a higher incidence (40.9% vs. 29.4%) and severity of AKI among those with COVID-19 compared to those with influenza.4
To compare the incidence and disease patterns of AKI between critically ill patients with COVID-19 and those with influenza, a local retrospective cohort study was initiated by HKUMed.1 The primary outcome of this study was the incidence of AKI, as defined by the KDIGO consensus criteria (increase in creatinine by 50% within 7 days or by 0.3mg/dL within 2 days) among the study population.1 Secondary outcomes included the incidence of stage 3 AKI, acute kidney disease (AKD) (defined as a confirmed diagnosis of AKI, or possessing a GFR of <60mL/min/1.73m2, or decrease in GFR by ≥35%, or increase in creatinine by ≥50% within 3 months), the need for renal replacement therapy (RRT) during hospital stay, mortality during hospital stay and 90-day mortality.1
A total of 4,328 patients were included in the final analysis, where 64.4% and 35.6% of patients tested positive for SARS-CoV-2 and influenza A virus respectively.1 Patients in the COVID-19 cohort were older, had a higher median Charlson Comorbidity Index (CCI), and were more likely admitted to the hospital emergently compared to the influenza A cohort (p<0.0001 for all).1 Furthermore, a higher proportion of the COVID-19 cohort were admitted to the ICU due to metabolic or renal causes compared to the influenza A cohort (p<0.0001 in both).1
Throughout the study period, the incidence of AKI was significantly lower in the COVID-19 cohort than in the influenza A cohort (37.8% vs. 53.7%; p<0.0001).1 In the subsequent analysis adjusted for potential confounders, patients with COVID-19 were associated with a significantly lower risk of developing AKI of any stage during their ICU stay compared to those with influenza A (adjusted odds ratio [aOR]=0.51; 95% CI: 0.42-0.61; p<0.0001).1
In terms of secondary outcomes, the COVID-19 cohort was associated with a significantly lower incidence of stage 3 AKI (15.5% vs. 24.3%; p<0.0001), AKD (66.2% vs. 76.4%; p<0.0001) and RRT (11.3% vs. 20.8%; p<0.0001) than those with influenza A.1 The adjusted analysis also indicated that COVID-19 infection was associated with significantly lower risk in developing stage 3 AKI (aOR=0.57; 95% CI: 0.45-0.72; p<0.0001), AKD (aOR=0.66; 95% CI: 0.53-0.82; p=0.0002) and requiring RRT (aOR=0.52; 95% CI: 0.40-0.67; p<0.0001).1 A further subgroup analysis consisting of patients with pre-existing CKD (n=1,391) also found that COVID-19 was associated with a significantly reduced risk of new AKI (aOR=0.61; 95% CI: 0.45-0.83; p=0.002) and new AKD (aOR=0.61; 95% CI: 0.43-0.86; p=0.0042).1
In summary, this Hong Kong-based retrospective study found that the incidence and risk of adverse renal outcomes were significantly lower among critically ill patients with COVID-19 compared to their counterparts with influenza A.1 Further investigation on the role of seasonal influenza vaccination and antiviral therapy in minimizing renal injury should be conducted.1
