Improvement of Sensitivity of Pooling Strategies for COVID-19

Figure 1

Given a population of 96 patients, infected samples are marked bold, and there are five infected samples in the 96-well plate. A single pooling approach of pool size 8 can be represented by 12 pools, each in a column, as demonstrated in (a), while the grid method tests not only the 12 vertically parallel pools but also 8 horizontally parallel pools as shown in (b). In the single pooling, there are five positive pools if all tests are error-free, and thus in the second, all the 40 samples appearing in these five pools need to retest individually, which yields a total of 52 tests across the 96 individuals and a 44/96 ≈ 45.8% improvement over the standard individual testing. However, in the grid method, only those samples appearing in both positive outcomes will be tested individually again to assess what status of COVID-19 it may have, so those appearing in a negative row or column can be excluded. Only those samples with bold circles will go to the second round. Therefore, there are total 40 tests across the 96 individuals being tested (8 rows plus 12 columns plus 20 remaining individuals), a 56/96 ≈ 58.3% (12/52 ≈ 23.0%) improvement over the standard individual testing (the single pooling), respectively. Note that the discussion above is made under the assumption that the experimental scenario is error-free, which is obviously not the case in the real world. Things become much more complicated if some test errors occur in the first stage of the grid method.

(a)

(b)