Asymptomatic persons contribute to widespread transmission of the severe acute respiratory
coronavirus virus 2 (SARS-CoV-2) and the coronavirus disease 2019 (COVID-19) pandemic.
Published reports from areas of high COVID-19 incidence in the United States suggest
that a significant percentage of asymptomatic persons are in healthcare systems. In
2 New York City (NYC) hospitals, 13.7% of asymptomatic pregnant women admitted for
delivery tested positive for SARS-CoV-2 virus.
Similarly, the nursing facility in Washington state with the earliest death from COVID-19
infection and the first healthcare worker infected in the United States, reported
>50% positivity of their asymptomatic residents for the virus.
Universal screening of healthcare populations may prevent in-hospital transmission
of SARS-CoV-2 virus. However, testing resources and personal protective equipment
(PPE) supplies to effectively isolate positive asymptomatic persons are currently
limited, resulting in provider safety concerns. Upon developing real-time reverse-transcriptase
polymerase chain reaction (rRT-PCR) tests in-house with >98% sensitivity, as well
as increasing the availability of PPE at our institution, we initiated universal screening
of patients on hospital admission using nasopharyngeal swabs to identify and isolate
asymptomatic positive patients to prevent in-hospital transmission of SARS-CoV-2.
We report our experience with universal screening of asymptomatic hospitalized persons,
including a comparison of demographics between symptomatic and asymptomatic populations.
On April 27, 2020, our 1,000-bed academic center instituted universal SARS-CoV-2 testing
of patients on hospital admission. Clinicians performed COVID-19 symptom screening
using clinical criteria reported in the literature.
They designated patients as symptomatic or asymptomatic when ordering the test. An
infectious diseases physician conducted chart review of asymptomatic positive patients
to confirm accuracy of classification. Asymptomatic patients were not isolated; test
turnaround time was 6–24 hours.
Statistical analyses were performed with the Fischer exact tests and paired t tests
to compare asymptomatic and symptomatic positive patients using SAS version 9.4 software
(SAS Institute, Cary, NC).
Between April 27, 2020, and May 18, 2020, when the hospital averaged at 60%–70% capacity,
we performed 1,811 SARS-CoV-2 tests on nasopharyngeal specimens: 1,335 (74%) were
asymptomatic, 420 (23%) were symptomatic, 56 (3%) were incorrectly ordered. Of the
1,755 tests in this analysis, overall positivity for SAR-CoV-2 virus was 79 (4.5%).
Of 79 patients, 12 were asymptomatic (15%) and 67 were symptomatic (85%). Of 1,335
asymptomatic patients, 12 tested positive, for a rate of ~ 1%. Of 420 symptomatic
patients, 67 tested positive, for a rate of 16%. No test converted to positive among
asymptomatic patients while hospitalized.
A comparative analysis of patients with positive SARS-CoV2 tests is listed in Table 1.
The mean age of asymptomatic patients was 37 years (SD, 19.71) versus a mean age of
59 years (SD, 13.08) among symptomatic patients (P = .0020). Hispanic patients were
more likely to be asymptomatic (7 of 12) than symptomatic (9 of 67) at the time of
testing (58% vs 13%; P = .0017). We observed no difference in positivity rate on admission
of asymptomatic versus symptomatic patients (P = .21). In addition, 5 asymptomatic
positive women were pregnant (5 of 12, 42%); no symptomatic patients were pregnant
(P ≤ .0001). A baby born to an asymptomatic SARS-CoV-2–positive mother tested positive
at 48 hours of life, and 1 asymptomatic, SARS-CoV-2–positive, immunocompromised patient
was receiving chemotherapy for breast cancer. One asymptomatic patient developed a
fever during hospitalization, and another was readmitted within 14 days of testing
positive, both of these events were not considered to be related to COVID-19.
Comparative Analysis Between Asymptomatic and Symptomatic Patients With Positive SARS-CoV-2
Demographic Characteristics of Asymptomatic Patients,SARS-CoV-2–Positive Patients(N
= 12, 0.62%)
Demographic Characteristics of Symptomatic Patients,SARS-CoV-2–Positive Patients(N
= 67, 3.5%)
Mean age, y (range)
37 (0–67)(SD, 19.71)
Mean age, y (range)
59 (12–78)(SD, 13.08)
Race/ethnicity, y (range)
Note. SD, standard deviation.
Universal screening for the detection of SARS-CoV-2 at our institution revealed that
during the study period, the number of asymptomatic persons admitted to the hospital
was relatively small. Our health system had a relatively low number of confirmed SARS-CoV-2–positive
COVID-19 patients (n = 82) admitted during the observed 3-week interval, compared
to 4,000 patients admitted to an NYC hospital reporting the use of convalescent serum
for the treatment of COVID-19 in a similar time frame.
Although low prevalence of asymptomatic patients has limited generalizability to areas
with higher rates of infection, it is valuable information for patients, healthcare
workers, and epidemiology programs in similar areas of COVID-19 prevalence.
During our study period, 7.6% of all admitted patients were Hispanic and 43.5% were
African American, yet 11 of 12 (91.7%) asymptomatic patients who screened positive
were African American or Hispanic. A similar trend was observed in other studies.
Furthermore, a higher proportion of pregnant women have asymptomatic infection, which
supports screening of peripartum women. Consistent with the literature, asymptomatic
patients were younger than those who presented to our healthcare system with COVID-19
The potential benefits of universal SARS-CoV-2 screening are many and are likely to
increase with escalating COVID-19 incidence. In hospitalized patients, detection of
asymptomatic infection can guide hospital isolation practices, bed assignments, and
the use of PPE.
For healthcare workers, it might improve workforce depletion by unnecessary quarantine,
reduce transmission in asymptomatic cases, contain the virus in healthcare settings,
and protect hospital staff from infection. In the community, mass testing can identify
asymptomatic cases and assist in eliminating the SARS-CoV-2 virus, as reported in
a village near Venice, Italy.
However, there are barriers to universal screening. Current testing capacity and test
turnaround time, staffing shortages, and availability of healthcare workers skilled
to perform nasopharyngeal swabbing currently limit widespread feasibility. Patient
discomfort from nasopharyngeal sample collection is another potential barrier to universal
This study has several limitations. The sample size was small, and the study was conducted
at a single center. In an area with high prevalence of COVID-19 infection, asymptomatic
screening would likely identify more asymptomatic cases. However, sensitivity of a
test in asymptomatic persons cannot be precisely defined. We add to the body of literature
on SARS-CoV-2 testing of asymptomatic patients at the time of hospital admission.
More data on universal screening is necessary to evaluate the clinical impact on healthcare
systems and to define optimal screening strategies of high-risk groups for asymptomatic