Abstract
Detection of SARS-CoV-2 is routinely performed in naso/oropharyngeal swabs samples from patients via RT-qPCR. The RT-LAMP technology has also been used for viral RNA detection in respiratory specimens with both high sensitivity and specificity. Recently, we developed a novel RT-LAMP test for SARS-CoV-2 RNA detection in nasopharyngeal swab specimens (named, N15-RT-LAMP) that can be performed as a single-tube colorimetric method, in a real-time platform, and as dry-LAMP. To date, there has been very little success in detecting SARS-CoV-2 RNA in urine by RT-qPCR, and the information regarding urine viral excretion is still scarce and not comprehensive. Here, we tested our N15-RT-LAMP on the urine of 300 patients admitted to the Hospital of Salamanca, Spain with clinical suspicion of COVID-19, who had a nasopharyngeal swab RT-qPCR-positive (n = 100), negative (n = 100), and positive with disease recovery (n = 100) result. The positive group was also tested by RT-qPCR for comparison to N15-RT-LAMP. Only a 4% positivity rate was found in the positive group via colorimetric N15-RT-LAMP and 2% via RT-qPCR. Our results are consistent with those obtained in other studies that the presence of SARS-CoV-2 RNA in urine is a very rare finding. The absence of SARS-CoV-2 RNA in urine in the recovered patients might suggest that the urinary route is very rarely used for viral particle clearance.
Highlights
The infection caused by SARS-CoV-2 (COVID-19) affects mainly the respiratory system, and the typical symptoms at onset are fever, dry cough, fatigue, and dyspnea
The 300 patients included in this study were divided into three groups of 100 individuals each according to the nasopharyngeal swabs RT-qPCR testing: PP, NP, and RP
The 100 urine RNA isolates from the PP group were analyzed by RT-qPCR in our laboratory
Summary
The infection caused by SARS-CoV-2 (COVID-19) affects mainly the respiratory system, and the typical symptoms at onset are fever, dry cough, fatigue, and dyspnea. Respiratory samples are considered the most efficient specimens for the isolation and detection of SARS-CoV-2 RNA, upper respiratory tract samples (nasopharyngeal or oropharyngeal swabs) in the early stages of infection, and lower respiratory tract samples in the later stages of infection (mainly sputum, if produced) [8]. Other clinical specimens such us saliva, stool, urine, serum, blood, tears [10,11,12] and seminal fluid [13] have been tested for the presence of SARS-CoV-2 with varying degrees of efficiency
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