Evaluating Hospital Admission Data as Indicators of COVID-19 Severity: A National Assessment in Qatar.

Background: Accurately assessing SARS-CoV-2 infection severity is essential for understanding the health impact of the infection and evaluating the effectiveness of interventions. This study investigated whether SARS-CoV-2-associated hospitalizations can reliably measure true COVID-19 severity. Methods: The diagnostic accuracy of SARS-CoV-2-associated acute care and ICU hospitalizations as indicators of infection severity was assessed in Qatar from 6 September 2021 to 13 May 2024. WHO criteria for severe, critical, and fatal COVID-19 served as the reference standard. Two indicators were assessed: (1) any SARS-CoV-2-associated hospitalization in acute care or ICU beds and (2) ICU-only hospitalizations. Results: A total of 644 176 SARS-CoV-2 infections were analyzed. The percent agreement between any SARS-CoV-2-associated hospitalization (acute care or ICU) and WHO criteria was 98.7% (95% confidence interval (CI), 98.6-98.7); however, Cohen's kappa was only 0.17 (95% CI, 0.16-0.18), indicating poor agreement. Sensitivity, specificity, PPV, and negative predictive value were 100% (95% CI, 99.6-100), 98.7% (95% CI, 98.6-98.7), 9.7% (95% CI, 9.1-10.3), and 100% (95% CI, 100-100), respectively. For SARS-CoV-2-associated ICU-only hospitalizations, the percent agreement was 99.8% (95% CI, 99.8-99.9), with a kappa of 0.47 (95% CI, 0.44-0.50), indicating fair-to-good agreement. Sensitivity, specificity, PPV, and negative predictive value were 46.6% (95% CI, 43.4-49.9), 99.9% (95% CI, 99.9-99.9), 47.9% (95% CI, 44.6-51.2), and 99.9% (95% CI, 99.9-99.9), respectively. Conclusions: Generic hospital admissions are unreliable indicators of COVID-19 severity, whereas ICU admissions are somewhat more accurate. The findings demonstrate the importance of applying specific, robust criteria-such as WHO criteria-to reduce bias in epidemiological and vaccine effectiveness studies.