key: cord-0710144-b20pbzi4 authors: Wong, Justin; Koh, Wee Chian; Momin, Riamiza Natalie; Alikhan, Mohammad Fathi; Fadillah, Noraskhin; Naing, Lin title: Probable causes and risk factors for positive SARS‐CoV‐2 test in recovered patients: Evidence from Brunei Darussalam date: 2020-06-19 journal: J Med Virol DOI: 10.1002/jmv.26199 sha: 04fab89e574d60f356fc00cd2f109dc141625aa7 doc_id: 710144 cord_uid: b20pbzi4 Case reports of COVID‐19 patients who have been discharged and subsequently report positive RT‐PCR again (hereafter referred as ‘re‐positive’) do not fully describe the magnitude and significance of this issue. In order to determine the re‐positive rate (proportion) and review probable causes and outcomes, we conduct a retrospective study of all 119 discharged patients in Brunei Darussalam up till April 23. Patients who were discharged are required to self‐isolate at home for 14 days and undergo NP specimen collection post‐discharge. Discharged patients found to be re‐positive were readmitted. We reviewed the clinical and epidemiological records of all discharged patients and apply log‐binomial models to obtain risk ratios for re‐positive status. One in five recovered patients subsequently test positive again for SARS‐CoV‐2 – this risk is more than six times higher in persons aged 60 years and above. The average Ct value of re‐positive patients was lower pre‐discharge compared to their readmission Ct value. Out of 111 close contacts tested, none were found to be positive as a result of exposure to a re‐positive patient. Our findings support prolonged but intermittent viral shedding as the probable cause for this phenomenon. We did not observe infectivity potential in these patients. This article is protected by copyright. All rights reserved. Current consensus on safe criteria for de-isolation of SARS-CoV-2 positive patients recommend the need for both clinical recovery of symptoms, and for those countries where testing and hospitalization capacity permits, two negative RT-PCR tests from respiratory specimens at 24 hours interval taken at least 8 days after symptom onset. 1 Notably though, there are reports from China, South Korea, and others of a number of patients who have met the discharge criteria and yet report positive RT-PCR again, from 2 to 13 days post-discharge. 2, 3, 4 As yet, no study has attempted to describe the Accepted Article magnitude and significance of this phenomenon which we term 're-positive'. This could complicate the management of COVID-19 patients. Up till April 23, 2020, Brunei Darussalam recorded a total of 138 COVID-19 cases of which 119 have been discharged. We conducted a retrospective cohort study of all discharged patients to identify those who are re-positive, describe their clinical and epidemiological outcomes, and analyse the predictors of re-positive status. COVID-19 surveillance in Brunei is mandatory under the Infectious Disease Act. All persons who meet the following criteria must undergo a nasopharyngeal (NP) swab for SARS-CoV-2 RT-PCR testing: (i) contact history in the last 14 days, regardless of symptoms, (ii) travel history in the last 14 days, regardless of symptoms, (iii) pneumonia, (iv) presents to a healthcare facility with respiratory symptoms for the second time within a 14 day period. In addition, sentinel surveillance is conducted at selected community health clinics and for the foreign worker population. 5 We confirmed SARS-CoV-2 by RT-PCR assay on nasopharyngeal (NP) specimens if the cycle threshold (Ct) values for Orf1ab was <40. A commercial kit (BGI Genomics) was used (sensitivity 82.5%, specificity 81.5%). 6 Specimens with Ct value > 30, were further re-tested for additional confirmation with TibMolBiol. All NP swabs (regardless of prior discharge status) are obtained by trained clinical staff (doctor or nurse) at a designated healthcare facility. Newly diagnosed patients are admitted to the National Isolation Centre (NIC) and monitored for at least 14 days from admission until two consecutive negative specimens collected at least 24 hours apart. Discharged patients are required to self-isolate at home, initially for a period of 7 days and later extended to 14 days. Verbal and written instructions for post-discharge selfisolation at home were given, including the requirement to stay in a separate bedroom from other members of the household. They undergo NP specimen collection at day This article is protected by copyright. All rights reserved. the earliest opportunity. Discharged patients found to be re-positive were readmitted. Bloods, chest X-ray, and antibody testing using the VivaDiag Rapid Test were conducted on readmission. This is a qualitative lateral flow immunoassay that has a reported specificity of 94.9% for IgG +/or IgM and a percentage positivity that range from 62.9% at 6 -10 days post-onset to 90.0% at >20 days post-onset. 7 Contact tracing was conducted for all close contacts of re-positive cases. A close contact was defined as any individual living in the same household, or someone who was within 1 meter of a confirmed case in an enclosed space for more than 15 minutes. All close contacts of confirmed cases were tested with RT-PCR. We review all discharged cases that had their post-discharge swab. We calculate the re-positive rate (percentage) by gender, age, clinical severity on first admission, and use of antiretroviral treatment (400 mg lopinavir/100 mg ritonavir) on first admission and apply log-binomial models to obtain risk ratios. We also compare pre-and postdischarge RT-PCR Ct values of re-positive patients using a paired t-test. Research Ethics Committee. 106 patients had a follow-up NP swab taken between 11 -18 days post discharge. 21 (19.8%) were found to be re-positive ( Figure 1 ). 12 were male and 9 female. The Routine blood and chest x-ray for all re-positive patients were normal. 14 (67%) of the re-positive patients had both IgM and IgG detected. We used Ct value as a proxy for viral load, with the value inversely related to RNA copy numbers. 8 The average Ct value of re-positive patients was lower pre-discharge compared to their readmission Ct value. This was statistically significant (p-value < 0.001) (Supplementary Table) . We compared re-positive rates of subgroups of four variables in Table 1 . The highest re-positive rate was observed in patients aged 60 and above (46.2%), followed by those with moderate to critical conditions (33.3%) and lopinavir/ritonavir treatment (30.3%). Multivariable log-binomial model identified age as the only significant risk This article is protected by copyright. All rights reserved. variable, with the highest risk in those aged 60 years and above (RR 6.21, 95% CI 1.20, 32.09) We report a 19.8% re-positive proportion. One patient reported mild symptoms on readmission, while the others were asymptomatic. Other studies have reported a lower re-positive proportion. A large national study in South Korea identified that 292 (3.3%) out of 8,922 recovered patients subsequently have at least one positive test post-discharge, however does not describe if all recovered patients were tested (as in our study), or if only those cases who were symptomatic were tested post-discharge. 9 This potential difference in case ascertainment criteria could account for the higher observed re-positive rate in our study. There were some observed differences between the two groups (re-positive and consistent negative). The associations with clinical severity and antiviral treatment were strongly attenuated in the multivariable model suggesting age as the key variable under consideration. No significant difference was observed for gender. We cannot exclude test performance or operator deficiencies in specimen collection as a contributing factor to our observed high re-positive rate. For other respiratory viruses, some studies have reported an overall sensitivity of between 65% and 78% by RT-PCR. 10 NP swabs may be less sensitive for SARS-CoV-2 during the convalescent period and as such could have resulted in false negatives on initial dischargehowever the need for two consecutive negatives should mitigate against this. 11 . Also, sampling and detection deficiencies cannot explain the higher risk in older individuals. This article is protected by copyright. All rights reserved. Some reports suggest reinfection as a possible cause; our findings do not support this. 12 There was no evidence of infection among close contacts which would have been likely if they were reinfected (given the need for an infective source). Moreover, 67% of re-positive patients in our study had antibodies on admission (however the correlates of protection are still to be defined which is necessary to be able to comment on the possibility of re-infection.). 13 20 (95%) patients were asymptomatic on re-detection, and negative RT-PCRs were observed in 16 patients soon (within 1 -3 days) after they were readmitted, suggesting This article is protected by copyright. All rights reserved. We observed that the re-positive rate is higher than commonly reported, with increased risk in older age groups. Our findings support prolonged but intermittent viral shedding as the probable cause for this phenomenon. We do not identify infectivity potential in these patients, however given the high re-positive rate observed, it would be dangerous to exclude this entirely. Based on our findings, we suggest that patients should be isolated for an extended period of time even after discharge. 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