Utility of ferritin, procalcitonin, and C-reactive protein in severe patients with coronavirus disease 2019

Objectives It is of clinical signi�cance to evaluate the disease severity and investigate possible biomarkers of COVID-19. In this study, we aim to describe the clinical characteristics of infection makers in severe and very severe patients with COVID-19. Methods This is a single center, observational analysis. We enrolled 48 in-hospital severe patients with COVID-19 admitted to the West District of Union Hospital of Tongji Medical College and analyzed infection biomarkers in 20 patients who had been tested for ferritin, PCT, CRP, etc. Results We noted signi�cantly increased CRP (1.48mg/L [IQR: 16.69-2.74] vs. 57.98mg/L [IQR: 38.335-77.565], P<0.05), PCT(0.05ng/ml [IQR: 0.03-0.06] vs. 0.21ng/ml [IQR: 0.11-0.42], P<0.05) and ferritin (291.13ng/ml [IQR: 102.1-648.42] vs. 1006.16ng/ml [IQR: 408.265-1988.25]) in severe COVID-19. For blood count, signi�cant increase was noticed in neutrophil count (3.75*10^9/L [IQR: 3.42-4.93] vs. 8.11*10^9/L [IQR: 5.675-8.905], P<0.05); and decrease was seen in lymphocyte count (1.62*10^9/L [IQR: 0.7-1.73] vs. 0.68*10^9/L [IQR: 0.385-1.04], P<0.05), and platelet count (214*10^9/L [IQR: 184-247] vs. 147*10^9/L [IQR: 126-202.5], P<0.05) in severe COVID-19.

Although most patients have mild symptoms and good prognosis, severe COVID-19 cases may present with acute respiratory distress syndrome (ARDS) and systemic in ammation.Thus, it is urgent to evaluate the disease severity and investigate possible biomarkers so as to make fast and correct clinical decisions.One recent study has pointed out that the patients with COVID-19 usually have increased serum C-reactive protein (CRP) (58.3%), lactate dehydrogenase (LDH) (57.0%) and erythrocyte sedimentation rate (ESR) (41.8%) 14 .But more evidence regarding other infection markers in COVID-19 needs further study.Of note, previous studies have established ferritin as a possible in ammation marker in pneumonia, associating with the progression of bacterial and viral infection.However, no evidence has been released how ferritin is altered in COVID-19.
In the present single center, observational analysis, we explored the infection biomarkers, including ferritin, procalcitonin (PCT), and CRP in in-hospital patients with severe and very severe COVID-19.We aim to describe the clinical characteristics of infection makers in severe and very severe patients with COVID-19.

Study design and participants
This is a single center, observational analysis.We enrolled 48 in-hospital severe patients with COVID-19 admitted to the West District of Union Hospital of Tongji Medical College in the 7 th oor ward from February 5 th to February 25 th , 2020, and analyzed infection biomarkers in 20 patients who had been tested for ferritin, PCT, CRP, etc. COVID-19 was diagnosed upon admission based on the New Coronavirus Pneumonia Prevention and Control Program (4th edition) published by the National Health Commission of China 6 .Severe COVID-19 was de ned as having either one of the owing criteria: 1) Respiratory distress with respiratory rate more than 30 times/min; 2) Oxygen saturation ≤93% in resting state; 3) PaO2/FiO2≤300mmHg (1mmHg=0.133kPa).And very severe COVID-19 was de ned as having either one of the owing criteria: 1) Respiratory failure in need of mechanical ventilation; 2) Shock; 3) Other organ dysfunction.Patients with previous medical history of acute coronary syndrome were excluded.The study was approved by the ethics committee of the local hospital and data were collected retrospectively.

Data collection and infection biomarker measurement
Demographic and epidemiological data including age, sex, and disease history were collected upon admission.Real-time polymerase chain reaction testing was used to detect COVID-19 according to the recommended protocol in the laboratory department of the hospital 15 .Serum samples were collected from the patients upon admission, and blood count, CRP, PCT, and ferritin were tested by the laboratory department.

Statistical analysis
All statistical analyses were performed by SPSS for Windows 25.0 (SPSS Inc.Chicago, IL).Data were presented as percentages for categorical variables and median±IQR (Inter Quartile Range) for continuous variables, unless otherwise indicated.Simple t test was used to compare continuous variables which are in normal distribution.Mann-Whitney U test was used to compare continuous variables which do not conform to the normal distribution.Fisher's exact test was used to compare categorical variables.Fisher's exact test was used to compare categorical variables.A value of p < 0.05 was considered statistically signi cant.

Results
9 patients with severe and 11 with very severe COVID-19 were included in this analysis.Baseline data for the cases enrolled were shown in Fisher's exact test was then applied to compare the rate with abnormal LDH, CRP, PCT, ferritin and blood count between severe and very severe COVID-19, and relative risk was calculated.The results showed that PCT and PLT count had statistical signi cance (P < 0.05), and CRP, ferritin and LY% had towards statistical signi cance (P = 0.07) (Table 3), indicating that PCT, CRP, ferritin, LY% and PLT count might be possible markers for the progression of disease in severe and very severe COVID-19.

Discussion
In this observational study, we have focused on the infection markers in severe and very severe patients with COVID-19.The serum levels of LDH, CRP, PCT and ferritin are markedly increased in very severe patients compared with severe COVID-19, suggesting that increased LDH, CRP, PCT and ferritin level might stand for more severe secondary bacterial infection and exacerbated COVID-19.Moreover, lymphocyte count is decreased in very severe patients compared with severe COVID-19, indicating that lower lymphocyte count correlate to poor prognosis in COVID-19.
In the present analysis, we rstly evaluated serum ferritin levels in COVID-19, which are signi cantly elevated during critical infection.The function of ferritin including iron binding and storage is associated with the immune and in ammatory response 16 .The reasons of increased ferritin include bacterial and/or viral infection, hemochromatosis and long-term transfusion 17 .When bacterial and/or viral infection takes place, the increase of serum ferritin is related to the release of iron in the reticuloendothelial system, the decrease of the ability of transporting ferritin in liver and spleen, and increased synthesis and release of intracellular ferritin 18,19 .Some studies showed that patients with bacterial infection had higher ferritin level compared to viral infection 20,21 .Previous review has also proposed a model that the in ammatory response to viral (IL-18/ferritin) presents as speci c plasma patterns of immune biomarkers 17 .Moreover, elevation of serum ferritin levels predicts a poor outcome in hospitalized patients with in uenza infection 16 .In the present study, the patients in severe and very severe COVID-19 both exhibits increase serum ferritin level, but the serum ferritin in very severe COVID-19 group is signi cantly higher than that of severe COVID-19 group.The increased ferritin might indicate severe secondary bacterial infection in COVID-19, and might be utilized as a marker of poor prognosis.
As we known, when in ammation or tissue damage happens, CRP can be signi cantly increased in serum, which is usually used as a unique in ammatory marker in the current clinical practice 22 .On the other hand, PCT, as the precursor of calcitonin, is a kind of glycoprotein without hormone activity, which is signi cantly higher in bacterial infection, but remain normal or slightly increased in viral infection 22,23 .Consistently, our study shows that CRP and PCT are markedly increased in severe and very severe COVID-19, and signi cantly higher in very severe COVID-19.This further correlates to the implication of the

Conclusion
In the present study, we investigated the infection markers in patients with severe and very severe COVID- serum ferritin alteration, that most of severe patients in COVID-19 have viral infection and secondary bacterial infection.One important limitation of the present study is that we have only observed infection biomarkers in limited COVID-19 patients; the small sample size have prevented us from reaching diagnostic value of infection markers in very severe COVID-19.Secondly, the present study hasn't evaluated the relationship between infection matkers and prognosis of all the patients enrolled.With more clinical information acquired from COVID-19 patients, further large population-based prospective studies coulf provide further evidence how infection biomarkers are altered and what it indicate in COVID-19.

Table 1 :
19, including serum levels of CRP, PCT and serum ferritin.Higher levels of CRP, PCT and serum ferritin in very severe COVID-19 as compared to severe COVID-19 might be correlated to secondary bacterial infection, protection from which could be of vital importance for reducing the mortality rate in very severe COVID-19.The study was approved by the ethics committee of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology.Written informed consent was obtained from all participants.Baseline Information of the Patients Enrolled Abbreviations: IQR: inter quartile range; CRE: Creatine; AST: Aspartate aminotransferase; ALT: Alanine aminotransferase; CK: Creatine Kinase; CKMB: Creatine kinase-MB; CK: Creatine Kinase; CKMB: Creatine kinase-MB.

Table 2 :
LDH, PCT and Blood Count in Severe and Very Severe Patients with COVID-19