Evaluation of PCR-based preimplantation genetic diagnosis applied to monogenic diseases: a collaborative ESHRE PGD consortium study.

Preimplantation genetic diagnosis (PGD) for monogenic disorders currently involves polymerase chain reaction (PCR)-based methods, which must be robust, sensitive and highly accurate, precluding misdiagnosis. Twelve adverse misdiagnoses reported to the ESHRE PGD-Consortium are likely an underestimate. This retrospective study, involving six PGD centres, assessed the validity of PCR-based PGD through reanalysis of untransferred embryos from monogenic-PGD cycles. Data were collected on the genotype concordance at PGD and follow-up from 940 untransferred embryos, including details on the parameters of PGD cycles: category of monogenic disease, embryo morphology, embryo biopsy and genotype assay strategy. To determine the validity of PCR-based PGD, the sensitivity (Se), specificity (Sp) and diagnostic accuracy were calculated. Stratified analyses were also conducted to assess the influence of the parameters above on the validity of PCR-based PGD. The analysis of overall data showed that 93.7% of embryos had been correctly classified at the time of PGD, with Se of 99.2% and Sp of 80.9%. The stratified analyses found that diagnostic accuracy is statistically significantly higher when PGD is performed on two cells versus one cell (P=0.001). Se was significantly higher when multiplex protocols versus singleplex protocols were applied (P=0.005), as well as for PGD applied on cells from good compared with poor morphology embryos (P=0.032). Morphology, however, did not affect diagnostic accuracy. Multiplex PCR-based methods on one cell, are as robust as those on two cells regarding false negative rate, which is the most important criteria for clinical PGD applications. Overall, this study demonstrates the validity, robustness and high diagnostic value of PCR-based PGD.

Healthcare workers' SARS-CoV-2 infection rates during the second wave of the pandemic: prospective cohort study

ObjectivesTo assess if healthcare workers during the second wave of the coronavirus disease 2019 (COVID-19) pandemic had increased severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates following close contact with patients, co-workers and persons outside work with COVID-19. MethodsA prospective cohort study of 5985 healthcare workers from Denmark were followed November 2020 to April 2021 and provided day-by-day information on COVID-19 contacts. SARS-CoV-2 infection was defined by the first positive polymerase chain reaction (PCR) test ever. Results159 positive and 35 996 negative PCR tests were recorded during 514 165 person-days. The SARS-CoV-2 infection rate following close contact with COVID-19 patients 3-7 days earlier was 153.7 per 100,000 person-days corresponding with an incidence rate ratio (IRR) of 3.17 (40 cases, 95% CI 2.15 - 4.66) compared with no close contact. IRRs following close contact with co-workers and persons outside work with COVID-19 were 2.54 (10 cases, 95% CI 1.30 - 4.96) and 17.79 (35 cases, 95% CI 12.05 - 26.28). The estimates for close contact with COVID-19 patients, co-workers or persons outside work were mutually adjusted. ConclusionsDespite strong focus on preventive measures during the second wave of the pandemic, healthcare workers were still at increased risk of SARS-CoV-2 infection when in close contact with patients with COVID-19. Among all health care workers, the numbers affected due to close patient contact were comparable to the numbers affected following COVID-19 contact outside work.