Analysis of the factors that affect the detection duration of SARS-CoV-2 in Loop Mediated Isothermal Amplification among COVID-19 inpatients.

In COVID-19 patients who are severe or immunocompromised, the duration of infectious viral shedding may be longer, and a longer isolation duration is recommended. In National Sagamihara hospital, a decline in the viral load to end the isolation of COVID-19 hospitalized patients is confirmed by loop mediated isothermal amplification (LAMP). However, a subset of patients persisted in displaying LAMP positivity for more than 20 days since symptom onset. Therefore, we conducted a retrospective observational study to investigate factors impacting the persistence of LAMP positivity. The study included 102 participants. The severity of COVID-19 was mild in 25.5%, moderate in 67.6%, and severe in 6.9% of patients. The median number (interquartile range) of days until negative LAMP since symptom onset was 16 (14-19) days. Multivariate logistic regression analysis showed that age ≥55 years and the delta variant were correlated with persistently LAMP positive for more than 20 days since symptom onset. This study identified that age, the delta variant, and oxygen requirement were factors contributing to persistently positive LAMP. Therefore, it is posited that in these patients, the implementation of LAMP for de-isolation would result in a prolonged duration of isolation.

Loop-Mediated Isothermal Amplification for Diagnosing SARS-CoV-2 Infection in Two School Children and a Neonate.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide and become a major public health problem. Although real-time reverse-transcription polymerase chain reaction (RT-PCR) is the gold standard for diagnosing coronavirus disease 2019 (COVID-19) and there are many reports discussing it, reports about loop-mediated isothermal amplification (LAMP) tests for SARS-CoV-2, especially in children, are limited. In this study, we present the results of LAMP test in three children with COVID-19 in a family cluster, and assess these results. The LAMP test results of these children showed a sensitivity and specificity of 63.6% and 100%, respectively, and that was comparable to the RT-PCR results. The results of both LAMP test and RT-PCR test using nasopharyngeal swab (NPS) were almost consistently similar in two school children throughout hospitalization except at the very early stages of infection. The preliminary results suggest that saliva samples would be less sensitive than NPS for LAMP testing in the late stages of infection, and that LAMP test would not provide accurate results in neonates.