Probabilities of SARS-CoV-2 infection before and after symptom screening*
| Pretest probability | Posttest probability | T+ | Posttest probability | T− | |
|---|---|---|---|
| SE = 0.986 SP = 0.549 (Table 4) | 0.001 | 0.0022 | 0 |
| 0.005 | 0.01 | 0.0001 | |
| 0.010 | 0.02 | 0.0003 | |
| SE = 0.922 SP = 0.548 (Table 5) | 0.001 | 0.002 | 0.0001 |
| 0.005 | 0.01 | 0.0007 | |
| 0.010 | 0.02 | 0.0014 |
Note: SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2, SE = sensitivity, SP = specificity.
↵* Pretest probability indicates the prevalence of SARS-CoV-2 infection in the population; posttest probability | T+ indicates the probability of having SARS-CoV-2 infection given a positive symptom screening; posttest probability | T− indicates the probability of having SARS-CoV-2 infection given a negative symptom screening. Test performance measures are from main results (Table 4) and from sensitivity analysis (Table 5). Of note, a pretest probability of 0.005 is about 7 times the prevalence of active cases in Alberta during the study period (0.07%).