SARS-CoV-2 RT-PCR as a universal screening on planned admission in asymptomatic patients

Universal screening for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on admission is reportedly beneficial in preventing nosocomial infections. However, some issues remain, including low positivity rate, cost, and time required for testing. We describe SARS-CoV-2 reverse transcription polymerase chain reaction (PCR) for universal screening in asymptomatic patients on planned admissions. In total, 14,574 patients were included between October 12, 2020, and June 23, 2022. The PCR-positive rate for the period was 0.44 % (64/14,574). The PCR positivity for the epidemic period by strain was 0.28 % (95 % confidence interval [CI] 0.12-0.56 %), 0.16 % (95 % CI 0.05-0.37 %), 0.21 % (95 % CI 0.09-0.41 %), and 0.9 % (95 % CI 0.65-1.2 %) for the wild-type strain, Alpha, Delta, and Omicron variants, respectively. The proportion of Ct values < 30 was higher in the first half of the epidemic (first vs. second, 29.4 % [95 % CI 16.9-44.8 %] vs. 16.7 % [95 % CI 6.0-28.5 %]), whereas that of Ct values >= 35 increased significantly in the second half (first vs. second, 32.4 % [95 % CI 19.3-47.8 %] vs. 70.0 % [95 % CI 53.5-83.4 %]). Of all positives, 50 % (32/64) had a coronavirus disease (COVID-19) history before PCR screening, with a median of 28 days (10-105) from COVID-19 onset or positive to PCR screening. PCR screening may help detect positives with high viral loads early in the epidemic for each mutant strain, with an increasing proportion of positives with low viral loads later in the epidemic. PCR testing may be unnecessary for recently diagnosed cases and patients in whom reinfection is unlikely.