Combining specimens from several low-risk inpatients in a single test for SARS-CoV-2 infection allowed hospital staff to stretch testing supplies and provide test results quickly for many more patients than they might have otherwise, researchers found.
Dr. Samir S. Shah
“We believe this strategy conserved [personal protective equipment (PPE)], led to a marked reduction in staff and patient anxiety, and improved patient care,” wrote David Mastrianni, MD, and colleagues from Saratoga Hospital in Saratoga Springs, N.Y. “Our impression is that testing all admitted patients has also been reassuring to our community.”
The researchers published their findings July 20 in the Journal of Hospital Medicine.
“What was really important about this study was they were actually able to implement pooled testing after communication with the [Food and Drug Administration],” Samir S. Shah, MD, MSCE, SFHM, the journal’s editor-in-chief, said in an interview.
“Pooled testing combines samples from multiple people within a single test. The benefit is, if the test is negative [you know that] everyone whose sample was combined … is negative. So you’ve effectively tested anywhere from three to five people with the resources required for only one test,” Dr. Shah continued.
The challenge is that, if the test is positive, everyone in that testing group must be retested individually because one or more of them has the infection, said Dr. Shah, director of hospital medicine at Cincinnati Children’s Hospital Medical Center.
Dr. Mastrianni said early in the pandemic they started getting the “New York surge” at their hospital, located approximately 3 hours from New York City. They wanted to test all of the inpatients at their hospital for COVID-19 and they had a rapid in-house test that worked well, “but we just didn’t have enough cartridges, and we couldn’t get deliveries, and we started pooling.” In fact, they ran out of testing supplies at one point during the study but were able to replenish their supply in about a day, he noted.
For the current study, all patients admitted to the hospital, including those admitted for observation, underwent testing for SARS-CoV-2. Staff in the emergency department designated patients as low risk if they had no symptoms or other clinical evidence of COVID-19; those patients underwent pooled testing.
Patients with clinical evidence of COVID-19, such as respiratory symptoms or laboratory or radiographic findings consistent with infection, were considered high risk and were tested on an individual basis and thus excluded from the current analysis.
The pooled testing strategy required some patients to be held in the emergency department until there were three available for pooled testing. On several occasions when this was not practical, specimens from two patients were pooled.
Between April 17 and May 11, clinicians tested 530 patients via pooled testing using 179 cartridges (172 with swabs from three patients and 7 with swabs from two patients). There were four positive pooled tests, which necessitated the use of an additional 11 cartridges. Overall, the testing used 190 cartridges, which is 340 fewer than would have been used if all patients had been tested individually.
Among the low-risk patients, the positive rate was 0.8% (4/530). No patients from pools that were negative tested positive later during their hospitalization or developed evidence of the infection.