Early-stage predictive markers of critically ill COVID-19 cases

Background: Severe cytokine storm syndrome (CSS) is considered as the cause of death among critically ill COVID-19 cases. Early identication of the high-risk severe cases is crucial to lower the fatality and healthcare costs. Methods: In this study, we retrospectively analyzed the rst and second-week serum levels of IL-6, IL-8, and IL-10 of 50 COVID-19 cases. We calculated the ratios of IL-6/IL-10 and IL-8/IL-10 at 3 rd , 6 th , 9 th , and 12 th days of hospitalization. Results: We collected 50 COVID-19 cases (male 54%, mean age 51.2, range 18 - 86), including 39 mild cases (78%), 7 severe/recovered cases (14%), and 4 died cases (8%).The ratios of IL 6/IL-10 and IL-8/IL-10 among mild cases were below 27 (the highest, 26.9) along the 4 testing points of two week hospitalization, while we found that the IL-6/IL-10 and IL-8/IL-10 ratios were as high as 187.51 and 225.3 respectively in the death group on 3 rd day with the highest IL-6/IL-10 ratio of 297.28 on the 6 th day of hospitalization. Conclusions: Our preliminary results suggest that the ratios of IL-6/IL-10 and IL-8/IL-10 at the early stage (the rst two weeks) of COVID-19 could be a predictive marker for the disease prognosis, of which the cut-off lines were suggested below 50 for a mild and recoverable severe cases.

hospitalization, while we found that the IL-6/IL-10 and IL-8/IL-10 ratios were as high as 187.51 and 225.3 respectively in the death group on 3 rd day with the highest IL-6/IL-10 ratio of 297.28 on the 6 th day of hospitalization.
Conclusions: Our preliminary results suggest that the ratios of IL-6/IL-10 and IL-8/IL-10 at the early stage (the rst two weeks) of COVID-19 could be a predictive marker for the disease prognosis, of which the cutoff lines were suggested below 50 for a mild and recoverable severe cases. Background COVID-19 pandemic has caused devastating damages to global economy and frightening human deaths worldwide. High transmissibility and fatality of COVID-19 has been an unprecedented challenge to global health. Even though over 80% of COVID-19 cases were mild, 20% of severe and critically ill cases has overburnt the healthcare system of countries with high epidemic. In the large number of death cases infected with COVID-19 virus, the cause of death is found to be due to immune disorders, manifested in immune impairment and cytokine storm production [1]. Early identi cation of the high-risk severe cases is crucial to lower the fatality and healthcare costs.In this study, we aimed to nd a early-stage predictive markers of critically ill COVID-19 cases.

Participants and sample collection
In this study, we retrospectively analyzed the rst and second-week serum levels of IL-6, IL-8, and IL-10 of 50 COVID-19 cases (male 54%, mean age 51.2, range 18 -86), including 39 mild cases (78%), 7 severe/recovered cases (14%), and 4 died cases (8%). All patients were hospitalized within the rst week of symptom onsets. The blood testing of each case was conducted at 3 rd , 6 th , 9 th , and 12 th days of hospitalization. We calculated the ratios of IL 6/IL-10 and IL-8/IL-10 among mild, severe/recovered and died cases.

Results
The ratios of IL 6/IL-10 and IL-8/IL-10 among mild cases were below 27 (the highest, 26.9) along the 4 testing points of two week hospitalization, while the severe/recovered cases had an up-then-down variation of IL-6/IL-10 and IL-8/IL-10 rations with the highest ratio of 45.3 at the 9 th day. Importantly, we found that the IL-6/IL-10 and IL-8/IL-10 ratios were as high as 187.51 and 225.3 respectively in the death group on 3 rd day with the highest IL-6/IL-10 ratio of 297.28 on the 6 th day of hospitalization. (Fig.1) The balance of pro and anti-in ammatory cytokines is crucial for human anti-virus immunity and prognosis of COVID-19 disease. Our preliminary results suggest that the ratios of IL-6/IL-10 and IL-8/IL-10 at the early stage (the rst two weeks) of COVID-19 could be a predictive marker for the disease prognosis, of which the cut-off lines were suggested below 50 for a mild and recoverable severe cases.

Discussion
Severe cytokine storm syndrome (CSS) is considered the cause of death among critically ill COVID-19 cases [2].IL-6 and IL-8 are the most important pro-in ammatory cytokines [3], while IL-10 is an antiin ammatory cytokine [4][5][6]. This study suggest that the ratios of IL-6/IL-10 and IL-8/IL-10 at the early stage (the rst two weeks) of COVID-19 could be a predictive marker for the disease prognosis.
In this study, all patients were hospitalized within the rst week of symptom onsets. Therefore, these three indicators can accurately re ect the in ammation and anti-in ammatory in patients.In the mild group, we found the ratio of IL-8/IL-10 was higher than IL-6/IL-10 along the 4 testing. However, IL-6/IL-10 levels were higher in the severe group. Study [7] has shown that the IL-6 level in mild patients was always very low, while IL-6 was drastically increased in severe patients. Interestingly, as IL-6, IL-8 stayed at a relatively stable levels within two weeks, and then went up on day 15-20 followed by a decline back to the initial level. This result is consistent with the present study.
In this study we found the cut-off lines,which were suggested below 50 for a mild and recoverable severe cases.However, the ratios of IL-6/IL-10 and IL-8/IL-10 were higher at the early stage in the died group.
This early-stage predictive markers may indicate a poor prognosis.The study [8] of SARS found that the ratio of IL-6/IL-10 at 2 th was 4, while the ratios of IL 6/IL-10 was below 2 at the 9 th day among the died gourp. The difference between COVID-19 and SARS virus is that the body can cause varying degrees of in ammation in the critical group. So the conclusion is that in early-stage the increasely in the ratio of pro and anti-in ammatory cytokines(above 50) indicates an enhanced collective in ammatory response, indicate a poor prognosis. Due to the limited number of cases included in this study, further studies are needed to validate our ndings.

Conclusions
We showed that, the ratios of IL-6/IL-10 and IL-8/IL-10 at the early stage (the rst two weeks) of COVID-19 could be a predictive marker for the disease prognosis, of which the cut-off lines were suggested below Abbreviations CSS: Severe cytokine storm syndrome; SARS: Severe Acute Respiratory Syndromes Declarations All participates/patients were consented orally to participate our study. Figure 1 Ratios of serum pro and anti-in ammatory cytokines among COVID-19 patients. (a) 39 mild cases; (b) 7 severe/recovered cases; (c) 4 died cases