Universal admission screening strategy for COVID-19 highlighted the clinical importance of reporting SARS-CoV-2 viral loads

Abstract

Previously limited to symptomatic patients, our hospital introduced a universal admission screening strategy for coronavirus disease 2019 on 25 April 2020. All patients were tested by RT-PCR. We observed decreased viral loads linked to increased screening of asymptomatic patients highlighting the fact that viral load values could guide infection control decisions.

Keywords: Asymptomatic patients; RT-PCR; coronavirus disease 2019; infection control; pre-hospitalization; screening; severe acute respiratory disease coronavirus 2; viral load.

Fig. 1

Median viral load value of positive SARS-CoV-2 RT-PCR was compared across two periods: the epidemic period (left), during which mainly symptomatic patients were screened, and the post-epidemic period (right) when all patients were tested on hospital admission. A decrease of median viral load (with an increased number of specimens with viral loads <1000 copies/mL) was observed during the universal screening period when many individuals tested were asymptomatic. Patient samples analysed using the GeneXpert test and showing only an N-positive PCR are displayed below the quantification limit. Cycle threshold values (Ct) were converted to viral loads using the formula –0.27Ct + 13.04 [3,4] generated using purified viral RNA and synthetic plasmids, kindly provided by the Institute of Virology of the University of Berlin, la Charité. Significance of viral load decrease was assessed using the non-parametric Wilcoxon–Mann–Whitney test with p ≤ 0.0001. m, viral load median value; n, number of positive samples; n_tot, total number of tests; pos, percentage of positive tests.