key: cord-0800123-75u4tazo
authors: Peng, Denggao; Zhang, Jing; Ji, Yiling; Pan, Dongming
title: Risk factors for redetectable positivity in recovered COVID‐19 children
date: 2020-10-21
journal: Pediatr Pulmonol
DOI: 10.1002/ppul.25116
sha: 0b4b2932a63bdfde9325df819c79508357a0c9dc
doc_id: 800123
cord_uid: 75u4tazo

OBJECTIVE: To identify the risk factors for redetectable positivity (RP), and to provide a basis for prevention and control of coronavirus disease‐2019 (COVID‐19) in children. METHODS: A retrospective study was performed on all pediatric patients diagnosed with COVID‐19. RP was defined as the positive result of real‐time reverse transcriptase polymerase chain reaction (RT‐PCR) for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) after symptom resolution and discharge. Children were defined as being less than 18 years old. RESULTS: Fourteen out of 38 (36.8%) pediatric patients exhibited RP. Compared with the non‐RP group (n = 24), the RP group (n = 14) had more family cluster infections, relatively higher white blood cell (WBC) count and longer plasma prothrombin time (PT), while age and gender were insignificant. T lymphocyte subclassification was observed at five‐time points: the first test after admission, 2 weeks, and 1, 2, and 3 months after discharge. The RP group had a higher percentage and count of CD8+ T lymphocytes and lower CD4+/CD8+ ratio at 2 weeks, while a lower percentage and count of CD4+ T lymphocytes and lower CD4+/CD8+ ratio at 2 months. The positive rate of nasopharyngeal swabs by RT‐PCR was higher during the onset, while that of anal swabs was higher during the recovery of COVID‐19. CONCLUSIONS: Family cluster infection, higher WBC count, and longer PT are the early risk factors for RP in recovered COVID‐19 children. The dynamic changes in number and ratio of CD4+ and CD8+ T lymphocytes may be involved in prolonged SARS‐CoV‐2 clearance. Nasopharyngeal swabs sampling during the onset and anal swabs sampling during the recovery may improve the positivity rate of RT‐PCR.

patients has been reported. 4 Our hospital also reported that 38 of the 262 discharged patients were found to have RP during the convalescence phase. Among them, patients younger than 14 years old exhibited more commonly RP compared with those between the ages of 14 and 60 years. 5 In the long-term follow-up, we also observed that a large proportion of pediatric patients showed RP (nasopharyngeal and/or anal swabs) after discharge, even repeated RP and several readmissions. Theoretically, RP means that SARS-CoV-2 in the patient's body may not been completely cleared or is experiencing reinfection. It undoubtedly has a serious impact on the formulation and implementation of prevention and control measures.

Despite great advances in rapid detection, diagnosis, and treatment in SARS-CoV-2 infection, little is known about the risk factors for RP.

In particular, data on convalescent children as a special population have not been reported. We aimed to identify the risk factors for RP, and to provide a basis for prevention and control of COVID-19.

This investigation involving human participants were reviewed and approved by the Ethics Committee of The Third People's Hospital of Shenzhen (approval number: 2020-139). Written informed consent from the patients was not required to participate in this study in accordance with the national legislation and the institutional requirements. Patients' personal information will be strictly protected.

RP was defined as the positive result of RT-PCR of the patient's specimen for SARS-CoV-2 after symptom resolution and hospital discharge. Children were defined as being less than 18 years old. We followed the guidelines on the diagnosis and treatment of SARS-CoV-2-induced pneumonia (the sixth edition draft) issued by the National Health Commission of China. 6 RT-PCR was used to detect SARS-CoV-2 positive in nasopharyngeal swab samples to confirm the diagnosis. Because of the need for epidemic prevention and control, all weakly and dubious positive RT-PCR results were regarded as positive. All diagnosed children were admitted to the designated hospital (the Third People's Hospital of Shenzhen) for isolation and treatment, and relevant examinations were completed as routine procedures. Fever was recognized when body temperature is higher than or equal to 37.3℃. Respiratory symptoms included nasal congestion, runny nose, sneezing, sore throat, cough, expectoration, chest pain, and dyspnea. Digestive symptoms included nausea, vomiting, abdominal pain, and diarrhea. All chest computed tomography (CT) images were reviewed by two experienced pediatric radiologists.

If unilateral or bilateral lung fields had any of the following features: Discharge criteria: All clinical symptoms of the COVID-19 children resolved, absorption of lung lesions improved, and two consecutive nasopharyngeal and/or anal swabs specimen of RT-PCR for SARS-CoV-2 were negative at least 24 h apart.

Follow-up procedure after discharge: All discharged COVID-19 children were isolated and observed at home for 2 weeks. Follow-ups occurred every 2 weeks for at least once after isolation. All individuals with RP were readmitted to the Third People's Hospital of Shenzhen for further medical observation. Close contacts of individuals with RP were also isolated and observed at home for 2 weeks. The rest of the recovered individuals without RP were closely followed-up in designated hospital outpatient clinics.

RT-PCR monitoring procedure for SARS-CoV-2: During the hospitalization and readmission of COVID-19, RT-PCR detection of nasopharyngeal and/or anal swabs specimen were performed every 3 or 4 days. During the follow-up period, it was done at each followup outpatient clinic. During the home isolation period of pediatric patients after discharge and close contacts of RP, community health workers visited the house twice weekly to collect nasopharyngeal and/or anal swabs. Inclusion criteria: all confirmed pediatric cases. Exclusion criteria: lost follow-up cases. [13] [14] [15] [16] [17] [18] [19] [20] [21] vs. 16 [12-22.5] ), and coinfection (7.1% vs. 8.3%) were not statistically significant. There was no patient who was severely ill.

Eight (33.3%) out of 24 cases in the control group and four (28.6%) out of 14 cases in the RP group were asymptomatic, 11 (45.8%) and three (21.4%) presented with fever, 12 (50%) and 10 (71.4%) presented with respiratory symptoms, one (4.2%) and three (21.4%) presented with digestive symptoms, seven (29.2%) and three (21.4%) presented with fever and respiratory symptoms, and one (4.2%) and three (21.4%) presented with respiratory and digestive symptoms.

There was no statistical difference between the two groups. Twenty (83.3%) out of 24 cases in the control group and 12 (85.7%) out of 14 cases had positive CT findings, of which 10 (41.7%) and eight (57.1%) were bilateral, 10 (41.7%) and four (28.6%) were unilateral, seven (29.2%) and nine (64.3%) presented with ground-glass opacities, seven (29.2%) and one (7.1%) presented with consolidations, three (12.5%) and one (7.1%) presented with ground-glass opacities and nodules, two (8.3%) and one (7.1%) presented with consolidations and nodules, and one (4.2%) and zero (0%) presented with consolidations and small pleural effusion. Fibrous cord or linear opacities and lymphadenopathy were not observed in any of the patients. There were two (8.3%) cases with respiratory syncytial virus coinfection in the control group, and one (7.1%) case with influenza B coinfection in the RP group ( Table 1 ).

The RP group had a relatively higher WBC count (7. (Tables 2 and S1 ). In addition, there were no statistically significant differences in indicators related to liver and kidney function, Troponin I (Table S1 ).

Twelve (50%) out of 24 in the control group and 10 (71.4%) out of 14 in the RP group had humoral immune function tested. There were no statistical differences in IgG, IgA, IgM, C3c, and C4 between the two groups (Table S2) with nodules, and one (7.1%) presented with fibrous linear opacities.

Pleural effusion and lymphadenopathy were not observed (Table S3) . Figure 1E ). The WBC counts were as follows: 14 (100%), 13

(92.9%), 11 (78.6%), 7 (50%), and 6 (42.9%) out of 14 in the RP group and 24 (100%), 9 (37.5%), 11 (45.8%), 9 (37.5%), and 4 (16.7%) out of 24 in the control group (Table S5 ). In the first 2 months after discharge, the WBC count in the RP group was always higher than that in the control group, and it continued to decline, reaching the lowest point at 2 months, but there were no statistically significant differences between the two groups ( Figure 1F) . 

Among 38 pediatric patients, we observed, most of them had mild symptoms or were asymptomatic, and none of them were severely ill, which was consistent with the report by Zachariah et al. 9 Our study found that children have a higher percentage of RP compared with adults. Compared with the control group, the RP group had a higher proportion of family cluster infections. Family cluster infection indicates that SARS-CoV-2 may be very infectious and has the ability of sustained person-to-person transmission. 10, 11 According to our Abbreviations: APTT, activated partial thromboplastin time; hs-CRP, high sensitivity C-reactive protein; IL-6, interleukin-6; PCT, procalcitonin; PT, prothrombin time; RP, redetectable positivity; WBC, white blood cell.

observation, close contacts of individuals with RP generally had their clinical symptoms resolved first, and whose SARS-CoV-2 nucleic acid also turned negative first. Also, they did not exhibit the onset of reinfection or RP during the follow-up period. Furthermore, recovered patients had to be isolated at home for 2 weeks after discharge and almost had no contact with the outside world. Therefore, the possibility that individuals exhibiting RP were reinfected by other patients is very low. RP is more likely to mean that the previously infected SARS-CoV-2 was not completely cleared, which has complicated decision-making around discontinuing isolation or home quarantine. 9 He et al. 12 observed the highest viral load in throat swabs at the time of symptom onset and inferred that infectivity peaked on or before symptom onset. These observations indicate that early droplet isolation and disinfection of the home environment may be the top priority for cutting off SARS-CoV-2 transmission in households and reducing RP. 13 The underlying viral clearance mechanism in children is still not completely understood. 14 CD4+ T lymphocytes are the center of the months. As far as we know, there is still no accurate answer to why the WBC in the RP group is higher than the control group. However, PCT, hs-CRP, and IL-6 are within the normal range and there is no difference between the two groups, suggesting that the impact of coinfection is negligible. We speculate that this may be related to the weak response of the innate immune system and the reduction of WBC depletion.

The coagulation cascade is activated during viral infections. This response may be part of the host's defense system to limit the spread of a pathogen. 22 However, excessive activation of the coagulation cascade can be deleterious. Tissue factor appears to be the major activator during viral infection. 23 Tang et al. 23 found that nonsurvivors of COVID-19 showed significantly higher levels of D-dimer, longer PT, and APTT. 23 We also observed a similar change. Compared with the control group, the PT and APTT of the RP group were 27 It has recently been reported that SARS-CoV-2 may exist in the gastrointestinal tract for a longer time than the respiratory system, and viral RNA remains positive in stools of pediatric patients for longer than 4 weeks. 26 These studies suggest an urgent There are several limitations in our retrospective cohort study. First,

due to the small sample size of the single-center research hospital, logistic regression analysis cannot be used to control confounding factors.

Second, the patients may be in different stages of COVID-19 when they are admitted to the hospital. Third, some children's lymphocyte subclassification data is missing at certain time points, which may not reflect the true difference. Therefore, these results should be carefully interpreted owing to potential selection bias and residual confounding. Larger cohort studies from other cities in China and other countries may also be needed to provide further data support. 

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The authors thank Professor Raymond F. Regan, Department of Emergency Medicine, University of Maryland School of Medicine, USA, and Cindy Acon Chen, USA, for reviewing this manuscript.

All authors have no financial relationships relevant to this article to disclose. Writing-review and editing: Denggao Peng.

http://orcid.org/0000-0002-1926-4474