At a time where the nations laboratories are continuing to struggle with meeting the COVID-19 testing demand, some officials have recommended the strategy of pooled testing as a means to cut down on the overall testing cost and workload.
Pooled testing, which was first developed during WWII as a means to test large groups of incoming soldiers for syphilis, is the process of taking individual specimens and combining them into a pooled specimen. If the pool produces a positive result, each specimen must then be tested again individually to confirm positives. However, a negative test for the pool alleviates the need for additional testing and allows those specimens to be confirmed as negative for just the cost of a single test.
That being said, it’s important to consider that pooled testing is generally most effective when the expected rate of positive cases is low, generally less than 10 percent. The obvious downside is that once a pool produces a positive result, each specimen must be tested again, which in turn increases the number of overall tests needed for that pool due to the pool test itself.
To avoid this pitfall, specimens should ideally be divided by whether they are symptomatic or not. By doing so, the amount of retesting required can be kept to a minimum and cost savings can be realized.
Experts have recommended pools of five to 10 specimens would typically be most appropriate, although larger pools may be utilized depending on the sensitivity of the test being utilized. With lower-sensitivity tests, positive samples could potentially be diluted and may not read as such when tested in a pool with several negative specimens.
While this process will clearly cut down on the number of tests, reagents and other supplies a lab uses while at the same time increasing efficiency, getting test manufacturers on board to alter their EUA-approved tests for pooled testing may be a separate hurdle given that it would cut into their revenue by reducing the volume of tests a lab utilizes.
Reach out to us if you have questions about implementing pooled testing or if you would like assistance setting up this process for your lab.