Abstract
OBJECTIVES: To examine circulating calprotectin and deoxyribonuclease (DNase) serum levels during hospitalization in COVID-19 patients, their continuity post-discharge and dynamics in relation to disease severity. METHODS: Serum levels were measured in samples collected from 252 COVID-19 patients during hospitalization (admission, days 3-5 and 7-10), at 3 months and after 1 year, and related to admission to intensive care unit (ICU) or high dependency unit (HDU), and 60-day total mortality. RESULTS: During hospitalization, calprotectin and DNase levels were significantly elevated compared to healthy controls (HC). Calprotectin was increased in ICU/HDU patients compared to those at wards during hospitalization and in non-survivors compared to survivors during prolonged hospitalization. High calprotectin levels at admission were associated with male sex, PaO2/FiO2 ratio and national COVID-19 wave 2 and 3 compared to wave 1. High admission levels of both calprotectin and ferritin were associated with an approximately twofold higher odds ratio for ICU/HDU admission than either marker alone. DNase was lower at admission in non-survivors compared to survivors. Post-discharge, DNase but not calprotectin levels remained elevated extending to 1-year follow-up compared to HC. CONCLUSIONS: COVID‑19 non‑survivors showed persistently higher calprotectin levels during prolonged hospitalization, and elevated admission calprotectin was associated with later pandemic waves and poorer oxygenation. Incorporating calprotectin with ferritin improved prediction of ICU/HDU admission. DNase levels were lower at admission in non‑survivors, while overall DNase remained elevated from hospitalization through 1‑year follow‑up compared with HC, suggesting a possible role in long‑term COVID‑19-related immune alterations.