The Association among Cycle Threshold Value of RT-PCR, Viral Culture in Hospitalized COVID-19 Patients Receiving Corticosteroid Treatment
Keywords:
SARS-CoV-2shedding, Immunosuppressive drug, RT-PCR, Ct value, Isolation precautionAbstract
Background: During the COVID-19 pandemic era, the isolation period is a critical issue for bed management in hospitals. The cut-off time for isolation is controversy in COVID-19 patients receiving steroid treatment because the shedding time might be longer than patients who did not receive. The purpose of this study was to determine the infectivity period of SARS-CoV-2 by detecting cultivable virus. Objectives: The primary endpoint was the correlation between viral culture result and cycle threshold (Ct) value from the RT-PCR test. The secondary aim was the different of Ct values in each group. Methods: The cross-sectional study was conducted in Rajavithi Hospital, Bangkok, Thailand. We collected nasopharyngeal swabs (NPS) from COVID-19 infected patients, having symptoms at least 2 weeks, received steroid treatment as immunomodulator and performed virus culture during August to September 2021. We categorized patients into 3 groups by symptom duration. Results: Nasopharyngeal swabs (NPS) from 27 patients were eligible. 15 (55.6%) were female patients. The age was 64.715.7 year-old. Their symptom’s duration was 29.7
11.6 days. All patients received the dexamethasone or equivalent to 12.4
4.4 mg/day, with duration at 18.6
8.3 days. Also, 55.5% of patient received the methylprednisolone 404.2
154.3 mg/day, with 2.8
1.6 days. 23 (85%) patients had symptoms for over 20 days. All patients had SARS-CoV2- viral culture negatively. The value of Ct N gene (p = .27) and Ct ORF1ab gene (p = .17) were not difference among groups. IgM was detected in patients with symptom over 2 weeks. Conclusion: Our study showed the all patients had negative by viral culture. RT-PCR could be detected for more than 4 weeks and the Ct’s value were not difference. All patients had seroconversion since infection more than 2 weeks. Therefore, the duration of illness with seroconversion might be useful for stop isolation.
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