Common Biomarkers Associated with Delirium in Hospitalized Patients with COVID-19 at the Epicentre of Turkish Coronavirus Outbreak: A Case-Control Study.

Introduction: To investigate the differences in biochemical characteristics between Coronavirus Disease 2019 (COVID-19) patients with and without delirium in non-intensive care (IC) COVID-19 units was aimed.

Methods: This study was designed as an observational, single-centered, and case-control study consisting of 43 delirious patients and matched 45 non-delirious patients admitted to non-IC COVID-19 units. Delirium was diagnosed by a consultant psychiatrist according to the DSM-5 delirium diagnostic criteria. Independent variables such as laboratory tests at the time of admission, clinical features, and patient characteristics were obtained from electronic medical records by researchers. In the primary analyses, binomial logistic regression models were used to investigate the factors associated with delirium, which was identified as the outcome variable. Multivariate logistic models were then adjusted for potential confounding factors, including age, gender, history of neurocognitive disorders and Charlson Comorbidity Index (CCI).

Results: We observed higher levels of urea, d-dimer, troponin-T, proB-type natriuretic peptide, and CCI in patients with delirium compared to patients without delirium. We also observed lower levels of estimated glomerular filtration rate (eGFR), serum albumin, and O₂ saturation and a decrease in the length of stay at the hospital. After adjusting for confounding factors such as gender, age, and comorbidity, we found that urea (adjusted estimate=0.015; 95% Confidence Interval [CI]=0.058-0.032, P=0.039), urea/creatinine ratio (adjusted estimate=0.008; 95% CI=0.002-0.013, P=0.011), and troponin-T (adjusted estimate=0.066; 95% CI=0.014-0.118, P=0.014) were independent biomarkers associated with delirium.

Conclusion: Delirium is associated with higher urea levels and urea/creatinine ratios in COVID-19 patients. In addition, the relationship between troponin-T and delirium may help understand the potential link between the brain and the heart in COVID-19. Additional multi-centred studies with larger sample sizes are needed to generalise these results.