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FDA Approves 'Pooled Samples' to Speed COVID-19 Testing

lab technician analyzing samples

 

Thomas Tolstrup / Getty Images

Key Takeaways

  • Quest Diagnostics is the first to receive FDA approval to use pooled sampling to test for COVID-19.
  • Pooling allows for multiple people to be tested at once, reducing the amount of time required to test large numbers of samples.
  • Pooled sampling utilizes fewer resources, which means using fewer testing supplies.

Last month, the Food and Drug Administration (FDA) allowed for one existing COVID-19 diagnostic test to be used with pooled samples, meaning it is now approved to analyze more than one person's respiratory swab sample at once. The goal is to make testing more efficient.

Specifically, the FDA granted emergency use authorization (EUA) to Quest Diagnostics for its SARS-CoV-2 rRT-PCR test, allowing the lab to test up to four samples at once. The pooled samples must be collected in a healthcare setting, as opposed to at home.

What Is Pooled Sample Testing?

Pooled sample testing combines samples from multiple people and tests them as a group. Sample pooling allows for testing of more people while utilizing fewer testing resources.

Pooling is not a new technique. Pooling, also known as batching, has been used to screen blood donations for HIV or hepatitis. It was introduced by Harvard professor Robert Dorfman during World War II to test for syphilis in soldiers.

The FDA approved Quest Diagnostics to test up to four individuals at once. Rather than running each person's nasopharyngeal or oropharyngeal swab sample alone, pooled samples are combined and then tested in a batch.

  • A negative result means no further testing for that batch of people. 
  • A positive result means that at least one individual may be infected.
  • If there is a positive result, each sample is tested again individually.

“Sample pooling is an important step forward in getting more COVID-19 tests to more Americans more quickly while preserving testing supplies,” FDA Commissioner Stephen M. Hahn, MD, said in a press release. “Sample pooling becomes especially important as infection rates decline and we begin testing larger portions of the population.” 

During an online conference with the American Society for Microbiology in June, White House coronavirus response coordinator Deborah Birx, MD, specified how drastically pooling could increase testing.

"Pooling would give us the capacity to go from a half a million tests a day to potentially 5 million individuals tested per day by those poolings," Birx said.

Concerns About Sample Pooling

Not all experts are on board with this technique when it comes to testing for COVID-19.

"I don't agree with the concept of the sampling pool—I don't think it's an effective way to test," Major Tonita Smith, MSN, RN, a Chief U.S. Army public health nurse, tells Verywell. "From the research, this method is most useful in areas that have test shortages and low rates of positive cases. I believe testing all close contacts, regardless of symptoms, is most effective in reducing the transmission. Even if there are close contacts and only one comes back positive, we've still identified a positive person and therefore, can test their close contacts."

Pooling is most efficient in areas with low COVID-19 risk where results are expected to be negative. It would not be beneficial to use sample pooling in high-risk areas, such as nursing homes or states with high rates of COVID-19.

Another concern with sample pooling is that combining samples from too many people can cause a false negative. This happens when the uninfected samples dilute an infected sample.

"There is a concern that combining samples may make it more difficult to detect positives since pooling in the laboratory dilutes any viral material present in the samples," the FDA says. However, validation data from Quest Diagnostics showed the test correctly identified pooled samples containing positive specimens.

Why Sample Pooling Can Be Useful

The U.S. continues to face challenges when it comes to COVID-19 testing, from a lack of sufficient test sites to a shortage of swabs, reagents, and testing machines. Pooling allows labs to test more samples with fewer testing materials.

According to the Center for Disease Control (CDC), pooled sample testing could be useful in group scenarios like returning employees to a workplace. 

What This Means For You

By saving and extending resources, pooled sample testing could become a vital tool for schools and workplaces to monitor people's health. But keep in mind a negative result from pooled testing should not be considered definitive. If you receive a negative result but are experiencing COVID-19 symptoms, Quest Diagnostics says you should consider individual testing.

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Article Sources
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  1. Food and Drug Administration. Quest Diagnostics SARS-CoV-2 Real-Time RT-PCR Test - EUA summary.

  2. Dorfman R. The detection of defective members of large populations. Annals of Mathematical Statistics. 1943;14:436–440. doi:10.1214/aoms/1177731363

  3. U.S. Food & Drug Administration. Coronavirus (COVID-19) update: FDA issues first emergency authorization for sample pooling in diagnostic testing. Updated July 18, 2020.

  4. Centers for Disease Control and Prevention. Interim guidance for use of pooling procedures in SARS-CoV-2 diagnostic, screening, and surveillance testing. Updated August 1, 2020.