Considerations for Group Testing: A Practical Approach for the Clinical Laboratory

Abstract

Group testing, also known as pooled sample testing, was first proposed by Robert Dorfman in 1943. While sample pooling has been widely practiced in blood-banking, it is traditionally seen as anathema for clinical laboratories. However, the ongoing COVID-19 pandemic has re-ignited interest for group testing among clinical laboratories to mitigate supply shortages. We propose five criteria to assess the suitability of an analyte for pooled sample testing in general and outline a practical approach that a clinical laboratory may use to implement pooled testing for SARS-CoV-2 PCR testing. The five criteria we propose are: (1) the analyte concentrations in the diseased persons should be at least one order of magnitude (10 times) higher than in healthy persons; (2) sample dilution should not overly reduce clinical sensitivity; (3) the current prevalence must be sufficiently low for the number of samples pooled for the specific protocol; (4) there is no requirement for a fast turnaround time; and (5) there is an imperative need for resource rationing to maximise public health outcomes. The five key steps we suggest for a successful implementation are: (1) determination of when pooling takes place (pre-pre analytical, pre-analytical, analytical); (2) validation of the pooling protocol; (3) ensuring an adequate infrastructure and archival system; (4) configuration of the laboratory information system; and (5) staff training. While pool testing is not a panacea to overcome reagent shortage, it may allow broader access to testing but at the cost of reduction in sensitivity and increased turnaround time.

Pooled Testing Strategies for SARS-CoV-2 diagnosis: A comprehensive review

“…A key step in this approach is to ascertain an ideal pool size that conserves maximum resources with consistent testing performance( Abdalhamid et al, 2020b ). In multiple recent articles and preprints, ideal batch sizes for different ranges of prevalence along with the expected reduction in fraction of tests and costs are put forth based on various algorithms( Aragón-Caqueo et al, 2020 ; Brynildsrud, 2020 ; Gu et al, 2020 ; Rai et al, 2020 ; Regen et al, 2020 ; Tan et al, 2020 )…”

Implementation of SARS-CoV2 Screening in K–12 Schools Using In-School Pooled Molecular Testing and Deconvolution by Rapid Antigen Test

“…Pooled testing, a form of group test whereby individual specimens are combined prior to the laboratory test process, increases testing capacity while potentially reducing test costs. Many scientists and epidemiologists have advocated for pooled testing for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) in large population cohorts ( 2 – 5 ). Several strategies for pooled testing have been proposed.…”

Group Testing for SARS-CoV-2 Allows for Up to 10-Fold Efficiency Increase Across Realistic Scenarios and Testing Strategies

“…Some important practical considerations are time constraints, specimen conservation for multi-stage testing, and resource availability, as well as the actual execution of the test in the labs, such as variations in pipetting and sample collection. In particular, the decision at which stage the pooling is taking place (pre-pre analytical, pre-analytical, or analytical) is crucial for the expected turnaround time ( 69 ). All of these aspects need to be carefully considered before the establishment of massive pooled test policies.…”