Table 6:

Probabilities of SARS-CoV-2 infection before and after symptom screening*

Pretest probabilityPosttest probability | T+Posttest probability | T−
SE = 0.986
SP = 0.549 (Table 4)
0.0010.00220
0.0050.010.0001
0.0100.020.0003
SE = 0.922
SP = 0.548 (Table 5)
0.0010.0020.0001
0.0050.010.0007
0.0100.020.0014
  • 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%).