What Is Pooled Testing?
Organizations are increasingly using pooled testing to monitor the coronavirus because of the many benefits that this screening strategy provides. Pool testing, pooled testing, or batch testing is a testing strategy that combines multiple individual samples. This approach allows laboratories to use fewer resources and test more samples of a given population at a time. Several COVID-19 surveillance programs in schools and universities now utilize the pooled testing strategy to monitor the virus.
During pooled testing, laboratories combine multiple samples into a tube, analyzing multiple samples together as a single sample. Laboratories then perform a PCR test to detect SARS-CoV-2. If a “batch” or “pool” tests negative, no action is required. However, if a pool comes back positive, individuals from the pool need to re-test individually to determine which samples tested positive for SARS-CoV-2.
What is Surveillance Testing for SARS-CoV-2?
Surveillance testing monitors health-related information at a population level to determine the infection rate of a particular population. According to the CDC, surveillance for SARS-CoV-2 includes ongoing systematic activities such as the collection, analysis, and interpretation of health-related data. These activities are essential to planning, implementing, and evaluating public health practices.
The Pooled Testing Process
The pooled testing process starts by collecting individual samples. After specimens are collected, pools are formed, putting five to ten individual samples in a large tube. Samples arrive in the laboratory sealed, and barcoded. Laboratory technicians then read the barcode, de-cap the tube samples, dispense liquid into the tube. In some cases, technicians re-cap the tube sample in a 96 position rack in an ordered manner such that aliquots from a specific tube position can be transferred by pipette to specific wells in a 96 well microwell plates for further processing.
After the pre-analytical processing of samples, laboratories perform a PCR test to detect SARS-CoV-2. If a pool comes back negative, no further action is required. If a pool comes back positive, individuals must submit new samples that are then tested separately.
Pooled Testing Diagnostics Benefits and Disadvantages
Major benefits for pooled testing are decreased test costs and the ability to test more samples at a time. Because of this, pooled testing can be more efficient than individually testing samples of a large population.
However, scientists argue that accuracy is one major disadvantage of this strategy. According to the FDA, samples are diluted when tested together, and thus, less viral genetic material is available to detect. Because low viral genetic material can increase the chance of false-negative results, this strategy can work best when there is a low prevalence of cases.
Researchers at the Harvard TH Chan School of Public Health and the Broad Institute of MIT and Harvard have found ways to optimize pooled testing strategies during different scenarios. Research shows that pooled testing could identify as many as 20 times more infected individuals per day when compared to individual testing.
For more information on pooled testing, the CDC published a document entitled “Interim Guidance for Use of Pooling Procedures in SARS CoV 2 Diagnostic, Screening, and Surveillance Testing”.