As the coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to severely affect public health and the global economy, developing faster ways to detect positive cases is crucial.
The current surge of COVID-19 cases in many countries, particularly in the United States and India, may necessitate better testing strategies. This way, infected individuals will be isolated more promptly and prevent further potential spread.
Pooled testing for SARS-CoV-2 detection is instrumental for increasing test capacity while decreasing test cost. A team of researchers at Yale University determined the barriers to implementing pooled testing in United States laboratories.
The study, which appeared on the pre-print server medRxiv*, showed that many laboratories use many instruments in their testing procedures, varying in the number of samples each can process.
What is pooled testing?
Pooled testing occurs when samples from a group of people are combined and tested in a single batch. Labs collect individual biological samples, combining equal parts of each to create a “pool.”
Labs use pooling to allow them to test more samples with fewer testing materials. This could be useful in scenarios like returning groups of employees to a workplace. Also, it helps reduce the cost of testing individual samples.
If a pooled test returns negative, all samples can be presumed to be negative with a single test. If the pooled result is positive, each of the samples in the pool will need to be tested individually to see which samples are positive.
The U.S. Centers for Disease Control and Prevention (CDC) emphasizes that pooling should be used only in areas or situations where the number of positive test results is expected to be low, like in areas with a low prevalence of COVID-19 cases.
Barriers to pooled testing
In the current study, the team invited 362 laboratories that had contacted the Yale School of Public Health expressing interest in conducting the SalivaDirect test to participate in a survey to evaluate testing barriers and pooling strategies for SARS-CoV-2 testing.
The researchers received 90 responses from Clinical Laboratory Improvement Amendments (CLIA) certified labs between the survey period of December 9, 2020, and January 21, 2021.
Nearly half of the labs that responded were for-profit, while most conducted diagnostic testing and testing for general surveillance and screening for specific events.
The participants responded to an open-ended question about the barriers to pool testing. One common response is the lack of methods accepted by regulators and authorities like the Food and Drug Administration (FDA), CLIA, or laboratory directors.
Many labs expressed that a lack of clear protocols makes it hard for them to conduct pooled testing. This means that the demonstration of the efficacy of pooling in their setting is lacking.
Further, other labs reported that local case-positivity rates were too high to require pooling, despite recent lab-based data showing the benefit of pooling gives samples up to a 30 percent positive rate.
Labs reported that re-testing positive pools individually is too hard to manage and can be resource-demanding. The labs also noted that re-test samples of positive pools might disrupt the standard testing flow and staffing practices.
The additional logistics needed for following samples through the pooled method and the lack of software that can help track samples are also considered barriers to the full implementation of pooling in the U.S.
A higher test throughput, lower costs per set, and faster turnaround times are all margins for testing improvement. One solution recommended was to boost the number of samples per test.
“The need for testing will remain for the years to come. Pooled testing offers sustainable surveillance measures that support long-term programs, essential for the early detection of virus resurgence or the emergence of variants of concern,” the team explained in the study.
Pooled testing can help fight against COVID-19 to promptly isolate positive cases without the need to test individually. This test can save time, effort, and money, and at the same time, contribute to combating the current pandemic.
To date, 146,58 million cases have been reported since the pandemic began. Of these, 3.1 million people have died. The United States and India report the highest numbers of cases, reaching 32 million and 16.96 million, respectively.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.