Figure 1
Sample flowchart for RT-PCR testing for SARS-CoV-2 using different sample pooling strategies at a University hospital in the southwestern part of Germany between March 11 and July 5, 2020.
Table 1
Comparative characteristics of (i) random sample pooling and (ii) a targeted pooling strategy based on a simple questionnaire for SARS-CoV-2 PCR testing in the southwestern part of Germany between March 11 and July 5, 2020.
| Samples tested in pools (n) | PCR pools (n) | Pool positivity rate (%) | Average number of PCRs needed to obtain an individual’s test result1 | Average number of individual test results produced by one PCR test1 | |
|---|---|---|---|---|---|
| Random pooling | 6,012 | 725 | 14.6 | 0.27 | 3.8 |
| Questionnaire-based pooling | 19,800 | 1,684 | 1.2 | 0.09 | 10.9 |
[i] 1 These calculated scores derive from the sum of employed pool tests plus the number of subsequent individual PCR tests required to decode positive pools.
Table 2
Comparative evaluation of questionnaire-based vs. random pooling in samples originating from the same rehabilitation hospital on consecutive days in March 2020 in the southwestern part of Germany.
| Questionnaire used? | Assessed as | Pool size | Number of individuals | Number of pools | Pool positivity | Prevalence | PCRs needed to obtain 100 individual results | ||
|---|---|---|---|---|---|---|---|---|---|
| N | % | N | % | ||||||
| Yes | Low risk | 10–13 | 103 | 10 | 0 | 0 | 0 | 0 | |
| Intermediate Moderate risk | 5 | 45 | 9 | 3 | 33 | 4 | 8.9 | ||
| High risk | Single test | 29 | 0 | – | – | 8 | 27.6 | ||
| Total | 177 | 12 | 6.8 | 35.6 | |||||
| No | 10 | 150 | 15 | 5 | 33 | 6 | 4.0 | 43.3 | |
[i] The following risk stratification procedure was used for patients and staff of the rehabilitation hospital:
Low risk: Neither clinical symptoms nor known exposure to an individual with a positive SARS-CoV-2 test result
Intermediate Moderate risk: Either clinical symptoms or known exposure to an individual with a positive SARS-CoV-2 test result
High risk: New-onset clinical symptoms and known exposure to an individual with a positive SARS-CoV-2 test result
