Of staff in UK hospital 43% with week off for COVID symptoms were RT-PCR+ve.
Sensitivity of RT-PCR - no clear data - stated to be as low as 70%.
Investigate worst case 43%, compare with 24% best case
Sens: 70% to 85%
Spec: 98% (makes little difference).
Odds = prob/(1-prob)
When pre-test prob = 0.43, pre-test odds = 0.43/0.57 = 0.75
When pre-test prob = 0.24, pre-test odds = 0.24/0.76 = 0.32
RT-PCR does not have high sensitivity – high chance of false negatives.
Prevalence of COVID-19 in people with COVID like symptoms is high.
NEGATIVE tests do not RULE OUT COVID-19.
Probability of COVID-19 in RT-PCR-ve far too high to treat them as uninfected.