In the battle against Covid-19, the screening tool early identification and isolation of infected individuals is of strategic importance. Broadening monitoring through molecular testing across large sections of the population represents an organizational and cost challenge, which could be addressed through pool testing.
The scientific validity of this procedure and the optimal conditions for its effectiveness in relation to the pandemic were analysed by a study appeared in PlosOne by a team of researchers from the Department of Statistics, Computer Science, Applications “Giuseppe Parenti” (DISIA) together with the Institute for Study, Prevention and the Oncology Network (ISPRO) [“Pool testing on random and natural clusters of individuals: Optimization of SARS-COV-2 surveillance in the presence of low viral load samples” https://doi.org/10.1371/journal.pone.0251589].
“With this technique the biological material taken with different individual tests is diluted, mixed and then analysed in a single laboratory test,” Fabrizia Mealli and Michela Baccini, professors of Statistics and Medical Statistics respectively and co-ordinators of research together with Francesca Maria Carozzi of ISPRO explain. “Only if the group test is positive the analysis of the individual samples is carried out, with a considerable saving in terms of the number of tests to be carried out compared to a classical screening involving one test for each subject”.
The pool testing, according to the results of laboratory tests conducted in May-July 2020, is able to detect even infections with low viral load (the most difficult to detect if diluted in a group of all negative samples), provided that the analysed group does not exceed five individuals. The research, which confirms the group's assumptions made at the beginning of 2020, shows that this can reduce the number of tests by up to 70% and that the benefits become even more evident if you build groups not on a random basis but so that you include naturally connected subjects (family members, work colleagues, school mates).
“Operating on natural clusters increases the probability that more infected subjects can coexist in the same group: as a result, the dilution effect, which could mask the presence of a single low viral load, is mitigated and the number of individual tests to be performed subsequently is reduced,” Mealli and Baccini comment.
