In England and Scotland, hospitals discontinued universal admission testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections starting August 31, 2022, and September 28, 2022, respectively.
In a recent research letter published in JAMA Internal Medicine, researchers performed a time series analysis using public data sets from both nations to examine whether this discontinuation resulted in a surge in hospital-onset coronavirus disease 2019 (COVID-19) cases. Note that the first-order autoregressive structure of interrupted time series analysis accounts for temporal correlations of studied datasets.
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During the early phases of the COVID-19 pandemic, asymptomatic or presymptomatic people spread two-thirds of all SARS-CoV-2 infections, including nosocomial ones. The transmission risk of SARS-CoV-2 was high between patients sharing rooms, and even universal medical masking could not eliminate the transmission risk.
Thus, people began questioning whether universal admission testing was beneficial. While data on whether it reduced nosocomial infections is sparse; yet, it remains labor-intensive and time-consuming, which hampers primary care for patients in need of care.
About the study
In the present study, researchers used data from Public Health Scotland and National Health Service England for weekly counts of new hospital-onset COVID-19 cases between July 1, 2021, and December 16, 2022, defined as a SARS-CoV-2-positive reverse transcription-polymerase chain reaction (RT-PCR) test anytime within seven days of hospital admission.
Since the rate at which these cases occurred closely correlated with COVID-19 community prevalence, the researchers also estimated weekly incidence rates of these cases per 1000 community infections. It helped them assess the relative surge in new hospital-onset cases.
The United Kingdom (UK) Office for National Statistics (ONS) randomly selects households for weekly testing of the community prevalence of COVID-19, which avoids potential biases related to healthcare testing initiated by clinicians and patients. They used this COVID-19 infection survey data to determine the changes in this weekly rate after hospital admission testing.
The study spanned three periods, as follows:
i) period of Delta dominance between July 1, 2021, and December 13, 2021.
ii) period of Omicron dominance between July 1, 2021, and December 13, 2021, and August 30, 2022/September 27, 2022, in England and Scotland, respectively.
In the above two periods, universal admission testing was prevalent.
iii) period of Omicron dominance, when universal admission testing was not prevalent, lasted till December 16, 2022, in both nations.
Finally, the researchers performed a sensitivity analysis using community-acquired COVID–19-related hospitalizations as the denominator, where a p-value <0.05 deduced by a two-tailed test indicated statistical significance.
Ceasing universal admission testing in England and Scotland markedly increased hospital-onset COVID-19 cases relative to community-onset infections in both England and Scotland.
Unrecognized admission cases with SARS-CoV-2 infections caused infections in other patients and healthcare workers, which set up a chain of infected people. During the study period, Scotland had 46,517 COVID-19–related hospital admissions, of which 34,183 and 12,334 were community- and hospital-onset cases, respectively. Likewise, England had 518,379 COVID-19–related hospital admissions, of which 398,264 and 120,115 were community- and hospital-onset cases.
In Scotland, the average weekly rate of new-onset hospital COVID-19 cases per 1,000 community infections surged from 0.78 to 0.99 from the Delta dominance period to the Omicron dominance period and further to 1.64 after they ceased universal admission testing. The immediate relative level change in observed weekly rates was 41% (statistically significant) after they ended the practice of doing COVID-19 testing at hospital admission but not after Omicron became predominant.
Likewise, in England, the average rate of new-onset hospital COVID-19 cases per 1,000 community infections surged from 0.64 to 1 and further to 1.39 from the Delta predominance period to the Omicron predominance period and after they ceased universal admission testing. The immediate level change showed a relative increase of 26% (statistically significant) after they ended universal hospital admission testing but not after the Omicron became predominant. The study findings remained similar when using community-acquired SARS-CoV-2 hospitalization incidence as the denominator.
Overall, the study results demonstrated that nosocomial SARS-CoV-2 Omicron infections were common during the study period and caused crude mortality, with rate estimates ranging between 3% and 13%. Therefore, hospitals should carefully consider the aftermath of ceasing the practice of universal testing for SARS-CoV-2 infections at hospital admissions.