A newly identified coronavirus, designated as severe acute respiratory syndrome coronavirus 2 (SARS CoV-2), has spread rapidly from its epicenter in China to more than 150 countries across six continents. In this study, we have designed three reverse-transcription loop-mediated isothermal amplification (RT-LAMP) primer sets to detect the RNA-dependent RNA polymerase (RdRP), Envelope (E) and Nucleocapsid protein (N) genes of SARS CoV-2. For one tube reaction, the detection limits for five combination SARS CoV-2 LAMP primer sets (RdRP/E, RdRP/N, E/N, RdRP/E/N and RdRP/N/Internal control (actin beta)) were evaluated with a clinical nasopharyngeal swab sample. Among the five combination, the RdRP/E and RdRP/N/IC multiplex LAMP assays showed low detection limits. The sensitivity and specificity of the RT-LAMP assay were evaluated and compared to that of the widely used Allplex™ 2019-nCoV Assay (Seegene, Inc., Seoul, South Korea) and PowerChek™ 2019-nCoV Real-time PCR kit (Kogenebiotech, Seoul, South Korea) for 130 clinical samples from 91 SARS CoV-2 patients and 162 NP specimens from individuals with (72) and without (90) viral respiratory infections. The multiplex RdRP (FAM)/N (CY5)/IC (Hex) RT-LAMP assay showed comparable sensitivities (RdRP: 93.85%, N: 94.62% and RdRP/N: 96.92%) to that of the Allplex™ 2019-nCoV Assay (100%) and superior to those of PowerChek™ 2019-nCoV Real-time PCR kit (RdRP: 92.31%, E: 93.85% and RdRP/E: 95.38%).

There are reports that pregnant women infected with SARS-CoV-2 not only have increased morbidity but also increased complications and evidence of maternal and fetal vascular malperfusion on placental pathology. This was a retrospective study of pregnant women diagnosed with SARS-CoV-2 infection after March 2020. The results of reverse transcription polymerase chain reaction testing and IgM and IgG antibody testing of the amniotic fluid, cord blood, placenta, and maternal blood were confirmed at delivery. Placentas were evaluated histopathologically. The study included seven pregnant women diagnosed with SARS-CoV-2 infection during pregnancy at a mean gestational age of 14.5 weeks. Out of the seven women, five were infected during the first trimester. The mean gestational age at delivery was 38.4 weeks. The reverse transcription polymerase chain reaction results for maternal plasma, cord blood, placenta, and amniotic fluid were negative and IgG antibodies were detected in maternal plasma and cord blood. On placental pathology, maternal vascular malperfusion was found in only one case, fetal vascular malperfusion in four cases, and inflammatory changes were found in two cases. Pregnancy outcomes for women diagnosed with SARS-CoV-2 infection during early pregnancy are positive and it is likely that maternal antibodies are passed to the fetus, which results in a period of immunity.

Ryoo NH, et al. J Korean Med Sci. 2005 Feb;20(1):143-145. http://dx.doi.org/10.3346/jkms.2005.20.1.143

Park SK, et al. Ann Lab Med. 2016 Nov;36(6):614-616. https://doi.org/10.3343/alm.2016.36.6.614