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Impact of On-site Compared to Send-away Testing for SARS-CoV-2 on Duration of Isolation and Resource Utilization.

Rapid detection and isolation of COVID-19 patients is the only means of reducing hospital transmission. We describe the impact of implementation of on-site SARS-CoV-2 RT-PCR testing on reduction in result turnaround time, isolation duration, pathology test ordering and antibiotic use in patients who do not have COVID-19.


INTRODUCTION
Early detection and isolation are key measures in controlling transmission of COVID-19. 1 Reduction in testing turnaround times (TAT) and duration that patients who test negative for COVID-19 spend in isolation may help relieve healthcare burdens associated with preventing COVID-19 transmission. [2][3][4] On January 24, 2020, the first confirmed case of COVID-19 in Australia was admitted to our health network, Monash Health. 5 Our hospital at the beginning of the outbreak relied on the regional viral Reference Laboratory for SARS-CoV-2 testing. 6 As the pandemic developed, testing for SARS-CoV-2 was performed on-site in an attempt to reduce result TAT. Herein we report our experiences of how on-site compared to send-away SARS-CoV-2 testing impacted the duration of time patients who did not have a diagnosis of COVID-19 spent in isolation precautions and subsequent healthcare outcomes.

METHODS
We examined SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) results on respiratory specimens (nasopharyngeal swabs, endotracheal aspirates, sputum) We included all hospitalized patients in isolation precautions as determined by SARS-CoV-2 RT-PCR testing conducted during the study period. Indications for testing were as per National guidelines at that time. 7 Patients were excluded if the SARS-CoV-2 RT-PCR was positive or if results of testing did not affect isolation duration (i.e. they had other indications to remain in precautions).
The study period captured three phases of SARS-CoV-2 testing. Phase 1 ('send-away', 47.3 hours, p<0.001). There were lower rates of fever being a reason for testing in the early in-house group compared to the other two cohorts (p=0.003). To assess the change in result TAT within each study period, data was plotted, and a linear regression line was fitted (Supplementary Figure 1). Result TAT over the duration of the send-away phase slowed, which was not seen in the on-site phases.
Isolation-based outcomes are presented in Table 2. Median isolation time in the established on-site RT-PCR group (21.9 hours, IQR 18.6-27.8) was lower than the early on-site (39.8 hours, IQR 26.9-47.7) and send-away groups (66.8 hours, IQR 47.1-97.0), (p<0.001). Median number of routine blood tests was lower in the on-site populations compared to send-away (p<0.001). Antibiotic use was lower in the established on-site group compared to the send-away and early on-site cohorts (p=0.001). Oseltamivir use was higher in the established onsite group compared to the send-away and early on-site cohorts (p<0.001).

DISCUSSION
We investigated the impact of on-site SARS-CoV-2 RT-PCR testing compared to send-away testing on the time patients who do not have a diagnosis of COVID-19 spend in isolation precautions. We found that use of on-site RT-PCR testing was associated with reduced isolation time compared to send-away testing for patients who tested negative for SARS- This result although unsurprising, we believe is important. To our knowledge, no other study has assessed the impact of SARS-CoV-2 RT-PCR TATs on healthcare resource utilization.
Our results suggest that by performing testing on-site, TATs are reduced and with it, the associated costs of isolation requirements likely also reduce. Reduced respiratory virus RT-PCR TATs themselves have been demonstrated to reduce length of stay and healthcare costs. 8 In a 2015 Spanish study, rapid influenza RT-PCR testing of hospitalized patients decreased isolation time by 23.7 hours and reduced hospitalization costs by 70USD per patient. 9 Early on-site testing was also associated with reduced isolation times compared to send-away testing. We originally hypothesized that TATs during the early phase of on-site RT-PCR implementation may be longer than established send-away testing due to the labor required for implementing new testing protocols in a pandemic setting. Interestingly, we discovered TATs of samples sent to the reference laboratory slowed over the 14-day period. We surmise that through this time, testing load on the reference laboratory increased precipitously, highlighting one challenge of operating in pandemic settings.
We observed a positive correlation between number of routine blood tests and isolation duration. This was not observed for other secondary investigations. Clinicians may have felt Downloaded from https://www.cambridge.org/core. 28 Aug 2020 at 19:26:58, subject to the Cambridge Core terms of use.
inclined to recheck routine blood tests whilst waiting for RT-PCR results. This may suggest longer isolation periods serve no additional benefit to patients for number of impactful investigations received and may only add additional resource costs.
By observing distinct time periods in testing protocol at our health network, we attempted to provide insight into our testing practices as it unfolded throughout the pandemic. As such, generalization of our results is limited by our specific experiences. The study population also varied over the study period. Initial guidelines recommended testing patients with severe pneumonia before the indications were broadened. This led to disproportionate testing being associated with ICU admission, mechanical ventilation, and antibiotic use in Phase 1. We were also unable to measure the impact of our findings on patients with COVID-19.    *Patients with multiple tests were included in the group of their first recorded test for demographic purposes. Differences in sample numbers occurred as 21 patients had two or more RT-PCRs performed in the study period (two RT-PCRs n=20, three RT-PCRs n=1); and four patients had two separate isolation periods 1 Overseas travel taken in the last 14 days prior to admission