Relevance of cycle threshold values in mass screening by reverse-transcription-PCR during COVID-19 pandemic in Belgium: a decision-making support?

Aim: The Belgium's strategy against COVID-19 was partly based on mass screening. Here, we reported the results observed in a Belgian mass screening center. Materials & methods: Between October 2020 and February 2021, 32,089 samples were collected analyzed with reverse-transcription PCR (Thermo Fisher Scientific kits and apparatus). Patients were categorized according to their contagiousness (extrapolated from the cycle threshold [Ct] values and the recommendation of Sciensano). Results: We observed association between Ct values and age, with higher Ct observed in extreme age groups (<6 years and >75 years). Conclusion: The analysis of the evolution of the contagiousness of these patients tested twice within a 7-day period showed the relevancy of the recommendation edited by Sciensano.

Nationwide Harmonization Effort for Semi-Quantitative Reporting of SARS-CoV-2 PCR Test Results in Belgium.

From early 2020, a high demand for SARS-CoV-2 tests was driven by several testing indications, including asymptomatic cases, resulting in the massive roll-out of PCR assays to combat the pandemic. Considering the dynamic of viral shedding during the course of infection, the demand to report cycle threshold (Ct) values rapidly emerged. As Ct values can be affected by a number of factors, we considered that harmonization of semi-quantitative PCR results across laboratories would avoid potential divergent interpretations, particularly in the absence of clinical or serological information. A proposal to harmonize reporting of test results was drafted by the National Reference Centre (NRC) UZ/KU Leuven, distinguishing four categories of positivity based on RNA copies/mL. Pre-quantified control material was shipped to 124 laboratories with instructions to setup a standard curve to define thresholds per assay. For each assay, the mean Ct value and corresponding standard deviation was calculated per target gene, for the three concentrations (107, 105 and 103 copies/mL) that determine the classification. The results of 17 assays are summarized. This harmonization effort allowed to ensure that all Belgian laboratories would report positive PCR results in the same semi-quantitative manner to clinicians and to the national database which feeds contact tracing interventions.

Covid-19: contribution of clinical characteristics and laboratory features for early detection of patients with high risk of severe evolution.

BACKGROUND: The aim of this study was to identify early clinical and laboratory predictive factors of a severe coronavirus disease 2019 (COVID-19). METHODS: A retrospective study was conducted on adult patients hospitalized for COVID-19 in our hospital. Diagnosis was based on a positive real-time reverse transcription-polymerase chain reaction (RT-PCR) on nasopharyngeal samples. The cohort was divided into two groups, i.e. a favorable evolution (FE) group and an unfavorable evolution (UFE) group, including intensive care unit (ICU) and deceased patients.Results: A total of 198 patients were enrolled in the study, with 138 FE (70%) and 60 UFE (30%). Older age, male gender, comorbidities and dyspnea at admission constituted significantly worse prognosis factors. Among laboratory features, lymphocyte and platelet counts as well as corrected glomerular filtration rate were significantly lower in UFE patients, while neutrophil to lymphocyte ratio, inflammation biomarkers, creatinine, aspartate aminotransferase, lactate dehydrogenase (LDH), glycemia and D-dimer were significantly higher. Procalcitonin and LDH appeared as the most accurate variables according to receiver operating characteristic curves. CONCLUSIONS: This Belgian study revealed clinical and laboratory features able to predict high risk of ICU requirement, or even death, at admission time. These results provide a potential tool for patient's triage in a context of pandemic.Abbreviations: COVID-19: coronavirus disease 2019; ARDS: acute respiratory distress syndrome; DIC: disseminated intravascular coagulopathy; MOF: multi-organ failure; RT-PCR: real-time reverse transcription-polymerase chain reaction; UFE: unfavorable evolution; ICU: intensive care unit; EDTA: ethylenediamine tetraacetic acid; WBC: white blood cell count; Hb: hemoglobin level; PCT: procalcitonin; Na: sodium; K: potassium; PT: total protein, CRP: c-reactive protein; Cr: creatinine; ALAT: alanine aminotransferase; ALAT: aspartate aminotransferase; TB: total bilirubin, LDH: lactate dehydrogenase, FERR: ferritin; hs-Tnt: high sensitive-troponin T; cGFR: corrected glomerular filtration rate; QR: quick ratio; DDIM: D-dimer; FIB: fibrinogen; SD: standard deviation; IQR: interquartile ranges; ROC: receiver operating characteristics; ECMO: extracorporeal membrane oxygenation; NLR: neutrophil to lymphocyte ratio; AUC: area under the curve; BMI: body mass index.