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Rapid, Accurate Testing for SARS-CoV-2 Reaches Emergency Department Point of Care

The specter of a "twindemic" of influenza and COVID-19 has emergency and urgent care treatment centers bracing for a busy respiratory virus season. Clinicians may see an increase in patients with similar symptoms, but different requirements for diagnosis, treatment, and infection control measures that protect both patients and staff are needed.

"You have these patients coming in, they have symptoms, and you don't know for sure if they have SARS CoV-2, and understanding that is really critical to what you do next," commented Joanna Sickler, MPH, Senior Director, Medical Affairs, Roche Molecular Diagnostics. "If they do have SARS CoV-2, it requires the use of PPE (personal protective equipment), it requires certain cohorting, it really guides all of your decisions."

"So, in a world where you don't have that information, it means that you have to treat every patient like they have SARS CoV-2, and that gets very expensive," Sickler explained. "You're using up all of this equipment, the PPE that we don't have enough of, and there is only so much space where you can put people."

The advent of rapid, accurate molecular-based identification of SARS-CoV-2 at the point of care (PoC) can, however, help emergency and urgent care treatment centers provide more efficient and effective triage and guide appropriate patient management.

"The value of being able to quickly determine who has SARS CoV-2 is being able to cohort them properly, make sure they get the care they need, identify your influenza patients, cohort them separately, and then provide antiviral treatment if needed," Sickler said. "I think it’s going to make just a huge difference in the efficient use of resources in these settings.

Quantifying Clinical Impact of PoC SARS CoV-2 Testing

The differences in how inpatient treatment is accessed when rapid identification of SARS CoV-2 is available at admission were examined by Tristan Clark, MD, School of Clinical and Experimental Sciences, University of Southampton, Southampton, UK, and colleagues.1

The investigators described how delays in the turnaround time from a central laboratory lead to poor patient flow through clinical areas, and patients suspected of having COVID-19 grouped into assessment areas pending testing results. Given the shortages of single-occupancy rooms, these measures are likely to foster hospital-acquired SARS CoV-2 infections, according to the researchers.

"UK National Health Service (NHS) data suggest that large proportions of COVID-19 cases diagnosed in hospital during the first wave were acquired nosocomially," Clark and colleagues recounted. "Rapid, accurate diagnostic tests that can be done in admission areas are therefore urgently required."

In their investigation of the clinical impact of molecular-based testing of COVID-19 at point of care in acute admissions, the investigators compared the course of 499 patients presenting with possible COVID-19 who were tested at PoC, to a control group of 555 patients whose testing samples were sent to the central laboratory. The groups were similar in demographics and the comparative analysis, using a Cox proportional hazards regression model, controlled for age, sex, time of presentation, and severity of illness.

Clark and colleagues reported that the median turnaround time for the PoC testing was 1.7 hours and 21.3 hour for central laboratory PCR tests. The large difference between the groups remained after controlling for the range of patient variables. Of the patients who required hospital admission, the time from their staging for test results to transfer for inpatient care was a median 8.0 hours for the PoC group and 28.8 hours for the control group.

Those receiving PoC testing were transferred to different locations a mean of 0.9 times, compared to 1.4 transfers in the control group. In the study, 43 (14%) of 313 patients in the PoC testing group were transferred directly from the emergency department to their treatment unit, while none of the control group avoided additional staging.

Sickler noted that the turnaround times in both central laboratory and PoC have generally improved since the period of that study, but that the significant advantage in time and corresponding patient care logistics remains with PoC.

"And these are tests that are providing lab quality PCR (polymerase chain reaction) results, with the Roche device in 20 minutes and with the Cepheid device its 45 minutes, at the point of care," she said.

Sickler acknowledged, however, that current costs and availability make it unlikely that PoC PCR testing would be used in settings other than acute and urgent care treatment centers.

"In an ideal world, every single patient could have a result in 20 minutes that they knew was correct, but during a pandemic, we just have to use the tools we have in the way that makes the most sense," Sickler said. "Which is why something like the rapid antigen test provides value in an outpatient setting when PCR may not be available, where patients are less sick, and can go home and isolate and use conservative measures."

Assessing COVID-19 in Absence of PoC Testing

Without the availability of PoC PCR testing, and while central lab results are pending, initial triage and treatment decisions are based on clinical findings.  Olivier Peyrony, MD, PhD, Emergency Department, Saint-Louis Hospital, Assistance Publique-Hôpitaux de Paris, and colleagues emphasized that prompt identification of patients with COVID-19 "is mandatory" to avoid the spread of the virus by patients with mild or nonspecific symptoms, but caution against relying on the presence or absence of particular clinical signs or on the validity of temperature screenings.

"Whereas fever was reported in more than 90 percent of the patients hospitalized with COVID-19, we found that even if 78.2 percent of the patients reported fever, only 34.4 percent of the patients had a temperature greater than or equal to 38°C  and 56.7 percent had one greater than or equal to 37.5°C at ED (emergency department) triage," Peyrony and colleagues reported.

"It is possible that the temperature was initially decreased by antipyretics and subsequently increased during the ED stay. Nevertheless, temperature should not be used in isolation to exclude COVID-19," they warn.

In their study, which Peyrony and colleagues describe as the first to prospectively assess the accuracy of clinical findings for diagnosis of COVID-19 in emergency departments, the presence of anosmia was associated with a high clinical probability of COVID-19, and bilateral B lines on lung ultrasonography corresponded to a statistically significantly increased likelihood of COVID-19.2

Although PoC PCR-based testing is not yet widely available, Sickler indicated that there is ongoing strategizing to enhance its utilization. "We're starting to think about what the optimal use of a PoC PCR test is, what is the optimal use of a lab PCR test that can do testing at higher volumes versus what is the utility of a lower sensitivity, but more plentiful rapid antigen test."

"I don't think we have those answers right now, but we're definitely going to be developing the data in the near term, to know what to use where, and be better able to answer those questions and support public health," Sickler said.

Clark and colleagues agree with Sickler on the current need to prioritize rapid, molecular-based PoC testing of SARS CoV-2 for acute treatment admissions. They anticipate a future, however, when this PoC testing can be of benefit in a range of environments.

"In addition to testing symptomatic acute admissions to hospital, point-of-care testing could also be used for assessing elective  hospital admissions, primary care patients, hospital staff, and care home staff and residents, as well as for airport screening, school screening, and even population-level screening," posited Clark and colleagues.

References

1.  Brendish MJ, Poole S, Naidu VV, et al. Clinical impact of molecular point-of-care testing for suspected COLVID-19 in hospital (COV-19POC): A prospective, interventional, non-randomized, controlled study. Lancet Respir Med. 2020, Oct 8;S2213-2600(20)30454-9. https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30454-9/fulltext. Accessed Oct 25, 2020.

2.  Peyrony O, Marbeuf-Gueye C, Truong V, et al.  Accuracy of emergency department clinical findings for diagnosis of Coronavirus Disease 2019. Ann Emerg Med.  2020; 76:405-412.