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Follow-up Study of Long-time Positive RT-PCR in Stool Specimens From Asymptomatic Children Infected With SARS-CoV-2

Xie, Jun MD*,†,‡; Long, Xiaoru MD§,†,‡; Ren, Chongsong MBBS; He, Ronghui MMed; Yan, Xiaofeng MBBS; Li, Weiguo MMEd*,†,‡; Luo, Zhengxiu MD*,†,‡; Li, Qiu MD†,‡; Xu, Hongmei MD§,†,‡; Liu, Enmei MD, PhD*,†,‡

Author Information
The Pediatric Infectious Disease Journal: October 2020 - Volume 39 - Issue 10 - p e315-e317
doi: 10.1097/INF.0000000000002837
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Abstract

The outbreak of coronavirus disease 2019 (COVID-19) began by the end of last year and has rapidly broken out all over the world.1 Children often account for a small percentage of patients and have showed only mild illness. Common symptoms of COVID-19 include fever and dry cough, and some had diarrhea.2 Several studies have found that the SARS-CoV-2 viral RNA last longer in the stool than in the respiratory tract.3,4 The mechanism is not yet clear, and data are still limited in children, especially in those who are asymptomatic. Here, we report 4 cases of confirmed infection in children (3 asymptomatic and 1 with fever), in whom the viral RNA has lasted for more than 1 month in stool specimens. Besides, we compared the results of the 3 asymptomatic children with previously reported results of children with symptoms, who had been tested for viral RNA in the stool specimens on their follow-up stage.

CASE REPORT

Three children (cases 1, 2 and 3) were found to be asymptomatic for COVID-19; 1 had normal computed tomographic scan results, whereas the other 2 showed increased bronchovascular bundle in both lungs. Case 4 had fever with unilateral pneumonia. All 4 children showed mild illness, and none developed severe complications and were admitted to the pediatric intensive care unit for oxygen support. With supportive treatments, all children were discharged home after showing 2 consecutively negative reverse transcription-polymerase chain reaction (RT-PCR) test results in pharyngeal swabs. The follow-up after discharge showed no signs or symptoms such as fever or cough throughout the time until the last follow-up.

Laboratory findings of these patients on admission are shown in Table 1. Two children had increased lymphocyte count, and the other 2 showed normal lymphocyte count. Only case 2 showed increased white blood cell count (>9.5 × 109/L), whereas white blood cell counts of the other 3 children were within normal range. Elevation of platelets was observed in case 2. Three children in whom procalcitonin was measured showed normal procalcitonin values. Serum levels of albumin, aspartate aminotransferase and total bilirubin were normal in all the children.

TABLE 1. - Clinical Presentations and Laboratory Findings of the Patients
Variables Case 1 Case 2 Case 3 Case 4
Age and gender
 Age, y 9 6 4 9
 Gender Male Female Male Male
Clinical symptoms and CT scan
 Symptoms Asymptomatic Asymptomatic Asymptomatic Fever
 CT images Increased bronchovascular bundle Normal Increased bronchovascular bundle Unilateral pneumonia
Laboratory test
 Leucocytes (×109/L), (normal range, 3.5–9.5) 4.86 11.4 5.5 5.6
 Neutrophils (×109/L), (normal range, 1.8–6.3) 2.32 6.41 0.99 3.56
 Lymphocytes (×109/L), (normal range, 1.1–3.2) 2.25 4.37 3.94 1.72
 Platelets (×109/L), (normal range, 125–350) 266 367 134 251
 PCT (mg/L), (normal range, 0–0.25) NA 0.03 <0.05 0.05
 ALT (U/L), (normal range, 0–45) 14 23 13 19
 LDH (U/L), (normal range, 120–250) NA 267 213 499
 Albumin (g/L), (normal range, 40–55) 44.0 52.3 45.4 42.3
 TB (μmol/L), (normal range, 1.7–21) 4.1 5.8 4.5 4.3
 D-dimer (μg/mL), (normal range, 0–0.5) 0.12 NA NA 0.2
Duration of hospitalization days 23 18 12 20
Days of nucleic acid turning negative in pharyngeal swab (d) 21 12 11 12
Duration of the negative nucleic acid from pharyngeal swab to anal swab (d) 33 25 32 8
ALT indicates aspartate aminotransferase; CT, computed tomography; LDH, lactate dehydrogenase; PCT, procalcitonin; TB, total bilirubin.

Case 1 was admitted to Nanchong Central Hospital, Sichuan, whereas the other 3 cases were reported in Chongqing. We recorded the timeline of changes in nucleic acid testing results in pharyngeal and anal swabs. The duration until viral RNA in pharyngeal swabs turned negative was similar for the 4 children (21, 12, 11 and 16 days, respectively). However, after nucleic acid testing results turned negative in respiratory samples, viral RNA remained detectable in the stools of the 3 asymptomatic children for 33, 25 and 32 days, respectively, and for 8 days in case 4. As for case 1, we obtained the Ct values in throat swabs and anal swabs to show how it changed over time. Follow-up after discharge showed persistent positive RT-PCR test results of anal swabs, with negative throat swab test results. The anal swabs still tested positive until the last follow-up, that is, 31 days after discharge, or 54 days since the first positive result for nucleic acid testing (nucleoprotein gene Ct value, 26.42; ORF1ab Ct value, 27.84).

DISCUSSION

These cases provided evidence that the duration of positive results on nucleic acid testing in stool specimens persists long after throat swab results turned negative. In the follow-up period after discharge, all patients with COVID-19 had positive RT-PCR test results for stool specimen, with no clinical symptoms or imaging findings. It has been reported that SARS-CoV-2 nucleic acid was detectable in the stool of adults and children even after discharge.5–7 Our study found that the anal swab was still positive after 31 days of at least 2 negative throat swab tests. Some researchers have been able to isolate the live coronavirus from the stool of patients.8 More recently, one study revealed the expression levels of angiotensin-converting enzyme 2 as a receptor of SARS-CoV-2 in normal human tissue and found the highest expression in small intestine, while the lungs and colon showed medium expression,9 which suggests that the SARS-CoV-2 may more likely bind to the gastrointestinal tract compared with the lungs. No difference in expression levels between gender or age were reported. These data supported that gastrointestinal infection and potential fecal–oral transmission can last long after the respiratory samples have tested negative. Therefore, the stool specimens should be taken into consideration when it comes to case confirmation and discharge criteria.

Several studies have reported on the clinical characteristics of asymptomatic infection in children3,10 and have showed that the duration of positive SARS-CoV-2 nucleic acid in pharyngeal swabs was no different from that in asymptomatic children. Still, data are limited about the changes of nucleic acid in stool specimens in symptomatic children. Our study demonstrated that nucleic acid testing results of anal swabs remain positive for 30 days after pharyngeal swab results turn negative in asymptomatic children.

This study has limitations, including the small sample size and failure to obtain stool specimens during their first few days of hospitalization. And we did not get RT-PCR Ct values over time for all patients due to limited conditions. However, our study can be considered as an evidence for the management of asymptomatic children infected with SARS-CoV-2, and we provide new evidence for current criteria for diagnosis and discharge. Therefore, prospective and large-sample studies are needed for further research on RNA replication in stools of asymptomatic children infected with SARS-CoV-2 to provide more credible evidence for clinical practice.

ACKNOWLEDGMENTS

We thank the nurses and clinical staff in Nanchong Central Hospital and Chongqing Public Health Medical Center who are providing care for the patient.

REFERENCES

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Keywords:

SARS-CoV-2; reverse transcription-polymerase chain reaction; children; asymptomatic; stool specimens

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