<u>Background</u>

The variability of Covid-19 severity between patients has driven efforts to identify prognosticating laboratory markers that could aid clinical decision making. Procalcitonin (PCT) is classically used as a diagnostic marker in bacterial infections, but its role in predicting Covid-19 disease severity is emerging. We aimed to identify the association between PCT and Covid-19 disease severity in a critical care setting and whether bacterial co-infection is implicated.

<u>Methods</u>

We retrospectively reviewed Covid-19 patients with PCT levels measured in a critical care setting at our institution between February and September 2020. Laboratory markers including peak PCT values and a range of bacterial culture results were analysed. Outcomes were the requirement and duration of invasive mechanical ventilation as well as inpatient mortality.

<u>Results</u>

In total, 60 patients were included; 68% required invasive mechanical ventilation and 45% died as inpatient. Univariate analysis identified higher peak PCT levels significantly associated with both the requirement for invasive mechanical ventilation (OR: 3.2, 95% CI 1.3-9.0, p=0.02) and inpatient mortality (OR: 2.6, 95% CI 1.1-6.6, p=0.03). Higher peak PCT levels was an independent predictor of mortality on multivariate analysis (OR 3.7, 95% CI 1.1-12.4, p=0.03). There was a significant positive correlation between increased peak PCT levels and duration on invasive mechanical ventilation. No significant difference was found between peak PCT levels of patients with positive and negative bacterial cultures.

<u>Conclusions</u>

Elevated PCT levels in Covid-19 patients are associated with respiratory failure requiring prolonged invasive mechanical ventilation and inpatient mortality. This association may be independent of bacterial co-infection.

<u>背景</ u>

患者之间Covid-19严重程度的变异性促使人们努力确定有助于临床决策的预后实验室指标。降钙素（PCT）传统上用作细菌感染的诊断标志物，但在预测Covid-19疾病严重程度中的作用正在兴起。我们旨在确定重症监护环境中PCT与Covid-19疾病严重程度之间的关联，以及是否涉及细菌共感染。

<u>方法</ u>

我们回顾性研究了2020年2月至2020年9月间在我们机构的重症监护环境中测得的PCT水平的Covid-19患者。分析了包括PCT峰值和一系列细菌培养结果在内的实验室指标。结果是有创机械通气的要求和持续时间以及住院病人的死亡率。

<u>结果</ u>

总共包括60例患者。68％的患者需要有创机械通气，45％的患者因住院死亡。单因素分析确定较高的PCT峰值水平与有创机械通气（OR：3.2，95％CI 1.3-9.0，p = 0.02）和住院死亡率（OR：2.6，95％CI 1.1-6.6，p = 0.03）。在多变量分析中，较高的PCT峰值是死亡率的独立预测因素（OR 3.7，95％CI 1.1-12.4，p = 0.03）。峰值PCT水平增加与有创机械通气持续时间之间存在显着正相关。细菌培养阳性和阴性的患者的PCT峰值水平之间没有发现显着差异。

<u>结论</ u>

Covid-19患者的PCT水平升高与呼吸衰竭相关，需要长期的有创机械通气和住院死亡率。这种关联可以独立于细菌共感染。