Asymptomatic COVID-19 testing program provides clinically relevant data
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An asymptomatic SARS-CoV-2 patient admission testing program can provide clinically relevant data, even during periods of lower transmission in which testing can be limited to patients who are not fully vaccinated, a recent study showed.
“The inception of this study was during late spring, early summer 2021. Our hospital, like other hospitals, had adopted an operational screening program for COVID-19 in which all patients (both symptomatic and asymptomatic) were tested for SARS-CoV-2 upon hospital admission,” Jennifer L. Cihlar, DO, an infectious disease specialist in the division of infectious diseases at the Vanderbilt University Medical Center department of medicine, told Healio. “After over a year of COVID-19 under our belt at that time, our question was that with the use of other hierarchies of infection control to prevent SARS-CoV-2 transmission in the hospital, what was the impact of such admission screening for asymptomatic COVID-19?”
She said her colleagues wondered whether asymptomatic testing data could be analyzed in a deeper manner than “just capturing the positivity rates,” as other researchers had done, as well as what could be learned from the previous year’s screening results “to help analyze or inform scenarios of when to consider if de-escalation of asymptomatic admission testing for certain populations could be appropriate.”
In an effort to answer some of these questions, Cihlar and colleagues assessed SARS-CoV-2 nucleic acid amplification admission testing results for all asymptomatic patients across four distinct inpatient facilities between April 20, 2020, and June 14, 2021.
According to the study, positivity rates and the number needed to test (NNT) to identify one asymptomatic infected patient were calculated. The researchers then compared admission results with COVID-19 community incidence rates for the surrounding metropolitan service area.
In total, 51,187 tests were collected, with a positivity rate of 1.8%. The team found that asymptomatic admission positivity rates were significantly different during periods of high transmission compared with other transmission periods (2.3%; P < .05), whereas positivity rates were the highest among community hospital patients (2.6%) and the lowest among behavioral health patients (0.9%).
When analyzing data from all of the hospitals collectively, the NNT significantly met the “clinically meaningful” NNT threshold and was significantly different during high transmission periods compared with other transmission periods (NNT = 44; 95% CI, 41-47). During periods of other transmission levels, the NNT did not meet statistical significance, even though many point estimates fell near or met the NNT threshold of 100.
Additionally, the study demonstrated that across all transmission periods, fully vaccinated patients had a significantly lower positivity rate (0.7%) compared with those who were not fully vaccinated (1.9%; P < .05).
The researchers also found that positivity rates were higher among patients who were not fully vaccinated across all levels of transmission, but this difference was not significant for the substantial transmission period. They added that the NNT values between the vaccinated and non-fully vaccinated were significantly different during times of high transmission, as well as all transmission periods collectively.
Based on these findings, Cihlar said there may be a continued benefit for testing asymptomatic patients across all hospital settings even as infection rates decline because testing may be more “clinically meaningful” among those who are not fully vaccinated.
Moreso, she said hospitals could even consider limiting admission testing to non-fully vaccinated patients during periods of lower transmission.
“The question of utility of asymptomatic screening is an incredibly nuanced subject matter given there are many considerations to be had based on hospital type, private vs. semi-private rooms, lab resources, community transmission rates etc., the immune evasive nature of some of the COVID-19 variants etc.,” Cihlar said.
“While our analysis does not definitively answer the question of utility of asymptomatic admission laboratory screening with regard to number needed to prevent a case of nosocomial transmission as this is difficult outcome to determine in general, these findings can be used to guide discussions at other institutions regarding such this infection control practice,” she said.
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