Leukopenia of Asymptomatic COVID-19 Infections under 18 Years Old in Recovery Stage (Running head: Leukopenia of Asymptomatic COVID-19 Infections)

doi:10.21203/rs.3.rs-4117616/v1

Objectives

In December, 2019, a type of novel coronavirus which was designated novel coronavirus 2019 (2019-nCoV) by the World Health Organization (WHO) occurred in Wuhan, Hubei, China. There is limited information available on the epidemiological and clinical characteristics of patients under 18 years old in the recovery stage. To compare the difference of epidemiological and clinical characteristics of COVID-19 involving 25 patients under 18 years old in the recovery stage between confirmed and asymptomatic infections.

Methods

The retrospective, single-center cohort study of COVID-19 involving 25 patients under 18 years old in the recovery stage at Guizhou Provincial Staff Hospital in Guiyang, China, from January 29 to March 31, 2020; last date of follow-up was April 22. We collected and analyzed epidemiological, demographic, clinical, laboratory, radiological, and treatment data. The researchers compared the epidemiological and clinical characteristics of confirmed COVID-19 infections and asymptomatic infections.

Results

Among the 25 COVID infections under 18 years old, 16 (64%) were mild or moderate confirmed cases, and 9 (36%) were asymptomatic. The shortest treatment period was 6 days, the longest 26 days, and the average treatment period was 14 days. Four cases (44.4%) had visited Wuhan or had a living story in the city. There were 9 (100%) asymptomatic cases were familial cluster outbreak, with an average infection number was 6 cases among all families. The number of asymptomatic COVID-19 infections with leukopenia was significantly more than confirmed cases (p = 0.04).

Conclusions

Leukopenia mostly occurred in asymptomatic COVID-19 infections under 18 years old compared with the confirmed patients.

Trial registration:

The Chinese Clinical Trial Register (CCTR number: ChiCTR2000032458) registered this study retrospectively on 28 April 2020.

COVID-19

SARS-CoV-2

leukopenia

children

asymptomatic infections

Since December 2019, a type of novel coronavirus which was designated novel coronavirus 2019 (2019-nCoV) by World Health Organization (WHO) occurred in Wuhan, Hubei, China,(1) and then it spread to the entire country and even the entire world. (2, 3) On February 11, 2020, the WHO announced a new name for the epidemic disease caused by 2019-nCoV: 2019 Coronavirus Disease (COVID-19). As for the virus itself, the International Committee on Taxonomy of Viruses (ICTV) has renamed the previously provisionally named 2019-nCoV as severe acute respiratory syndrome coronavirus-2, SARS-CoV-2.(4) Researchers have not yet explored the origin of SARS-CoV-2, and early studies have found that wild animals such as pangolins were potential intermediate hosts of the virus (5, 6), Therefore, wild animals carried the virus initially, and now it is the first time it has invaded human beings.

Meanwhile, it also means that human's cognition of COVID-19 was not complete, and it was still in the process of exploration. China was the first country to experience COVID-19, and most of the early reported cases showed middle-aged and elderly people or who existed diabetes, hypertension and cardiovascular diseases were common, children were few. (7–10) However, as the epidemic spreads and the number of children cases gradually increases, we should pay more attention to the group of children because of their immature immune system. (11–13) We aim to compare and analyze the epidemiological characteristics and physiological test data of asymptomatic and symptomatic cohort, explored whether there were significant differences between the two groups, to provide a theoretical basis for later clinical diagnosis and related studies.

Design This is a retrospective, single-center cohort study of COVID-19 involving 25 patients under 18 years old from Guizhou Provincial Staff Hospital in the recovery period. We unveiled the CONSORT (Consolidated Standards of Reporting Trials) Flow Diagram of this study in Fig. 1. The Chinese Clinical Trial Register (CCTR number: ChiCTR2000032458) recorded the retrospective registration of this study by the researchers on 28 April 2020. URL: http://www.chictr.org.cn/edit.aspx?pid=52779&htm=4. On March 15, 2020, our team developed the protocol for this study.

Setting A tertial hospital of COVID-19 medical center in Guizhou Province.

Inclusion criteria All asymptomatic and confirmed patients under 18 years old with COVID-19. The records of a hospital information system (HIS) in Guizhou Provincial Staff Hospital provided us with all the data.

Exclusion criteria All asymptomatic and confirmed patients of age ≥ 18 years old.

Intervention No.

Main outcomes and measures Our analysis involved collecting and analyzing epidemiological, demographic, clinical, laboratory, radiological, and treatment data as main outcomes and measures. We compared the epidemiological and clinical characteristics of confirmed COVID-19 infections and asymptomatic infections.

Study Definition

Classification The standard for case classification in this study was based on COVID-19 diagnosis and treatment scheme, 1st to 7th edition. The classification of cases in this study relied on the COVID-19 diagnosis and treatment scheme, 1st to 7th edition. We categorized mild and moderate patients in the symptomatic group based on the national standards, while including asymptomatic patients in the control group.

Epidemic focus Since 2019-nCoV first appeared in Wuhan, Hubei province, and then spread to the entire country and even the entire world, most of the existing studies regard Wuhan or other areas of Hubei province as the Epidemic focus area.

Possible exposure time That is the maximum probability of infection with COVID-19.

Incubation period Theoretically, the incubation period is between onset infection and onset symptom. However, because a variety of factors affect the specific time of morbidity and make it impossible to calculate, we define the incubation period as the potential exposure time to the time allowed for admission to the hospital.

Treatment cycle We included the number of days in the treatment cycle in this study, which refers to the time from the first diagnosis to the definite detection showing the patient was cured, excluding the observation time transferred to the centralized isolation hospital.

Statistic Analyze

EXCEL software was used to arrange information, then choose suitable data imported into SPSS 26.0 for analysis. First, the method of mean sequence was used to process the missing values of the data. Considering the sample size was less than 40, Fisher's Exact method was used to analyze the difference of a class variable between the two groups. We used the independent sample T test to analyze quantitative variables that conformed to a normal distribution among the two groups. And we employed a non-parametric test of independent samples for variable data that did not adhere to normal distribution. All practices serve one purpose, to compare the differences in epidemiological characteristics and physiological detection data between the two groups.

CONSORT Flow Diagram (Fig. 1)

In this research, the whole cohort encompassed 137 cases with COVID-19 infections, including adults and children, as well as asymptomatic and confirmed COVID-19 infections. We compared the epidemiological and clinical characteristics of the two groups by dividing twenty-five cases under 18 years old into the asymptomatic COVID-19 infections cohort and the confirmed COVID-19 infection cohort.

Basic epidemiological characteristics

Disease type

Studies have shown that among the current cases who were sent to the hospital for treatment, COVID-19 was less severe in patients under 18 years old, with most cases being mild or moderate. COVID-19 was less severe in patients under 18 years old, and most of were mild or moderate.(14) However, there have been reports of critical illness in children at present(15). Among the 25 cases in this study, 16 (64%, 16/25) had appeared infection symptoms, and 9 (36%, 9/25) had no symptoms. It is important to note that asymptomatic patients did not exhibit any clinical symptoms, but this does not imply that they belong to patients with a mild infection. The severity of infection should be determined according to the duration of virus activity in the body. (16) Asymptomatic patients are infectious and can still cause a certain range of transmission. (17)

Gender and age composition

Among the asymptomatic patients in the study, 5 (55.6%) cases of the patients were male. In terms of age, the youngest patient was only over 5 months old, the oldest patient was 16 years old, the average age was 8.27 years old and the median age was 7 years old (inter-quartile range 6 to 10). While 16 symptomatic patients made up of 10 (62.5%) males. From age structure to see, the youngest patient was an infant who only over 2 months old, and the oldest patient was 17 years old, the average age was 9.6 years old, and the median age was 11 years ((inter-quartile range, 3.75 to 14.25). There was no significant difference in gender and age between the two groups (p = 0.53 and p = 0.34, respectively).

Incubation

In pneumonia cases infected by SARS-CoV-2 in patients under 18 years old, the incubation is as short as one day and as long as 14 days. In this study, the mean sequence method was used to process the data about 8 patients’ incubation absence. The median incubation period for symptomatic patients was 10 days (inter-quartile range, 7 to 10), and 15 patients (93.75%, 15/16) had an incubation period of less than two weeks.

Treatment circle

Previous studies have shown that the average treatment period of light and normal types was not over two weeks. Collectible statistics show that the shortest period of asymptomatic patients was 6 days, the longest treatment period was 26 days, and the average treatment period was 14 days. For people who have symptoms, the shortest treatment cycle was 4 days, the longest treatment cycle was 20 days, and the average treatment cycle was 12 days. The data showed that the average treatment circle of 9 asymptomatic patients was longer than two weeks and which was longer than symptomatic patients. However, there was no significant difference between the two groups in the treatment cycle.

History of epidemiology

According to the existing epidemiological data, people who had visited Wuhan or had a living story in the city or other areas of Hubei province were those with high incidence of COVID-19, and close family contact was the key cause of cluster outbreak in children. Among the asymptomatic patients, 4 (44.4%) had visited Wuhan or had a living story in the city or other areas of Hubei province. All the patients had a familial cluster outbreak, and the average familial infection number was 6. As to symptomatic patients, 9 (56.3%) had visited Wuhan or had a living story in the city or other areas of Hubei province. Fourteen patients (87.5%) had familial clustering, and the familial average infection number was 5. there was no significant difference between the two groups in the three characteristics.

Laboratory inspection

Among the asymptomatic patients in the recovery stage, 5 patients had decreased white blood cell count, 2 patients (22.2%) had increased lymphocyte absolute value, 3 patients had increased platelet count, and 4 patients had decreased neutrophils. Blood sedimentation was normal in all patients. Only 1 case (6.2%) of confirmed patients had decreased white blood cell count and 2 cases (12.5%) had increased in white blood cell count. Three (18.75%) patients had an increased absolute value of lymphocytes. Six (37.5%) patients’ platelet count had risen. Three cases (18.75%) showed a decrease in neutrophils. There were significant differences in leukopenia between the two groups (p = 0.04), but no significant differences in other laboratory test items.

Chest computerized tomography (CT)

All the 25 patients underwent chest CT scan after getting into the hospital. Only 1 (11.11%) case of the asymptomatic patients had the characteristics of pulmonary infection (Fig. 2), ground glass shadow change respectively located beside the right main bronchus in Panel A and dorsal inferior lobe of right lung in Panel B; Inflammatory consolidation shadows in the dorsal inferior lobe of right lung in Panel C and D. Eight patients (88.89%, 8/9) had no distinct changes. Five (31.25%, 5/16) patients with symptomatic infection, CT showed lesion change, and 11 (68.75%) patients had no change. The p value on CT suggested that there was no significant difference between the two groups. The CT of symptomatic patients did not change under the existing studies that there are a few patients with positive RT-PCR of throat swab test and a history of clinical characteristics and exposure in Hubei province, but there is no abnormal phenomenon in chest-CT examination. Although real-time reverse-transcription–polymerase-chain-reaction (RT-PCR) is the gold standard for the detection of COVID-19, it presents a high false positive rate because of the influence of sample sampling and clinical medication. In view of chest-CT is easy to perform. Similarly, it cannot achieve the complete accuracy of the detection results. Therefore, in order to guarantee the accuracy of test results, it is common to use both sample sampling and clinical medication together to measure COVID-19.

The occurrence of the 2019-nCoV in Hubei province aroused the attention of the provincial committee and government in Guizhou province, and then leading organization quickly plan prevention and control measures. Guizhou province had the least COVID-19 patients in southwest China except Tibet's autonomous region through joint effort. Since the first confirmed case of COVID-19 appeared in Guizhou province on January 13, 2020, the public health department actively executes joint prevention and control work, and launched the first-level response to public health emergencies on January 24, 2020. From January 13, 2020, the public health department actively carried out joint prevention and control work and implemented the first-level response to public health emergencies on January 24, 2020, until April 1, 2020, when they confirmed 147 COVID-19 patients, including 1 case imported from abroad, and identified 26 cases as children, accounting for 17.81% (26/146). In this study, there were 25 cases of children, have a proportion as high as 96.15% (25/26) of the cases in Guizhou province.

The reason that patients’ incubation period exist missing data is that 12 (48%, 12/25) children's age at 10 years old or younger, because of the young could not accurately describe onset time of their symptoms or even no memory about onset symptom. Another reasonable explanation is that asymptomatic patients have no obvious symptoms in the early stage of infection, so they are not aware of the fact of infection. In addition, the average treatment period among 9 asymptomatic patients was over two weeks and longer than 2 days for symptomatic patients, and 3 (33.33%) patients’ treatment period was over 3 weeks. The reason is that the long incubation period of asymptomatic patients made the virus survive in the body for a long time, and virus invasion was severe, so it needs to undergo a longer treatment cycle. The literature has proved that in the routine blood test of COVID-19 patients; it is common for the occurrence of decreased white blood cells or lymphocyte count (9, 18), and the number of white blood cells in both mild and moderate types mostly decreases.

In this study, 5 asymptomatic patients’ white blood cells had decreased, while only 1 symptomatic patient’s (6.2%) white blood cells had decreased and 2 (12.5%) cases had increased. There was a significant difference in white blood cells between the two groups (p = 0.04). Despite not showing any clinical symptoms, the 5 asymptomatic patients had already contracted SARS-CoV-2. The erosion of the virus caused excessive destruction of white blood cells, so the number of white blood cells in peripheral blood had decreased. However, white blood cell count increased in patients with symptomatic was indicative that the aggravation of the patient's condition. We considered the difference in the immune system and the ability to resist the virus in the two groups because of the significant difference in the white blood cell count.

Advantages and disadvantages of this study

There are several advantages to our study. First, this is the first study to use clinical inspection results and epidemiological survey data about COVID-19 in patients under 18 years old during the recovery stage. Second, the nature of our study was a retrospective analysis that compared symptomatic with asymptomatic patients to draw conclusions. Third, our study has revealed that leukopenia is predominantly present in asymptomatic patients under 18 years old with COVID-19 for the first time.

Certainly, there are some disadvantages and shortages in the research. For example, the sample size of this study was 25 patients, which was small and lacked credibility. In view of the small number of COVID-19 patients in Guizhou province, the sample size of patients under 18 years old with COVID-19 in this study was small, so more studies will verify our conclusion in the future.

In this study, most of the patients under 18 years old infected by SARS-CoV-2 were mild or moderate type. Leukopenia mostly occurred in asymptomatic patients under 18 years old with COVID-19 than in those with confirmed infections.

2019-nCoV	novel coronavirus 2019
COVID-19	2019 coronavirus disease
WHO	World Health Organization
ICTV	International Committee on Taxonomy of Viruses
SARS-CoV-2	severe acute respiratory syndrome coronavirus-2
CONSORT	Consolidated Standards of Reporting Trials
CCTR	Chinese Clinical Trial Register
URL	uniform resource locator
HIS	hospital information system
CT	computerized tomography
RT-PCR	real-time reverse-transcription–polymerase-chain-reaction

Ethics approval and consent to take part

We stated that we got written consent to take part from the parents or guardians of the minors who are under the age of 16, while patients aged 16-18 got it themselves. The Biomedical Ethics Committee of Affiliated Hospital of Zunyi Medical University approved this study.

Consent to publish

Not Applicable.

Availability of data and materials

We stated that all the data and materials were true and available in the study.

Patent Data

You or anyone else have not reported these patients in any other submission.

Competing interests

All authors have read and approved the final version of the manuscript and agree to submit it for consideration for publication in the journal. There are no ethical/legal conflicts involved in the article.

Funding

The study design, data collection and analysis, as well as the language edition, etc. of this research pater was supported by Science and Technology Support Plan of Guizhou Province in 2019 (Qian Ke He Support [2019] 2834) and Science and Technology Plan of Guizhou Province in 2020 (Qian Ke He Fundamental [2020] 1Z061).

Authors’ contributions

ZW had full access to all data in the present study and accepts responsibility for data management and accuracy of the data analyses. Study concept and design: ZW. Acquisition and interpretation of data: YSY. Drafting of the manuscript: YSY and WZ. Critical revision of the manuscript for important intellectual content: YSY and WZ. Administrative, technical, or material support: ZW and YSY. Study supervision: ZW. All authors agree to submission of the final version of this manuscript. ZW is the study guarantor.

Acknowledgements

The authors thank Ping Lu, Min Yao, Yang Hong, Jinhua Wu, et al. gave us selfish helps on the process of database construction of COVID-19 in this study.

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Table 1. Baseline and Clinical Characteristics of Patient Population with COVID-19 (n=25) *

	Patients No (%)		P value
Clinical Characteristics	Asymptomatic n=9 (36)	Symptomatic n=16 (64)	P value
Sex			0.53
Female	4 (44.4)	6 (37.5)
Male	5 (55.6)	10 (62.5)
Age (y) (median [25th–75th percentile])	7 (6～10)	11 (3.8~14.3)	0.34
Minimum	0.4	0.2
Maximum	16	17
Average	8.27	9.6
Mode	6	12.17
Incubation
(days median [25th–75th percentile])	-	10 (7~10)
Treatment Cycle			1.00
Minimum	6	4
Maximum	26	20
Average	14.4	12.4
(days median [25th–75th percentile])	11 (8~24)	13.5 (9.5~15)
Epidemiology Investigation
Epidemic Focus	4 (44.4)	9 (56.3)	0.69
Family Aggregation	9 (100)	14 (87.5)	0.52
Average Familial Infection Number	6	5	0.66
Laboratory data on admission
White blood cell count, ×10⁹/L			0.04*
< 4 >10	5 (55.6) 0	1 (6.3) 2 (12.5)
Lymphocyte count, ×10⁹/L			0.85
1.1~3.2 >3.2	5 (55.6) 2 (22.2)	10 (62.5) 3 (18.8)
Platelet count, ×10⁹/L			0.56
<100 >300	1 (11.1) 3 (33.3)	0 6 (37.5)
C-response protein, mg/L			0.27
<2 >2	8 (88.9) 1 (11.1)	11 (68.8) 1(6.3)
Neutrophils			0.056
<0.4	4 (44.4)	3 (18.8)
erythrocyte sedimentation rate			0.07
>standard value	0	5 (31.3)
CT			0.36
Change Un-change	1 (11.1) 8 (88.9)	5 (31.3) 11 (68.8)

*P<0.05

No competing interests reported.

Leukopenia of Asymptomatic COVID-19 Infections under 18 Years Old in Recovery Stage (Running head: Leukopenia of Asymptomatic COVID-19 Infections)

Status:

Version 1

Abstract

Objectives

Methods

Results

Conclusions

Trial registration:

Figures

Background

Methods

Study Definition

Statistic Analyze

Results

CONSORT Flow Diagram (Fig. 1)

Basic epidemiological characteristics

Disease type

Gender and age composition

Incubation

Treatment circle

History of epidemiology

Laboratory inspection

Chest computerized tomography (CT)

Discussion

Advantages and disadvantages of this study

Conclusions

Abbreviations

Declarations

References

Table 1

Additional Declarations

Status:

Version 1