NNT
number needed to test
Positivity rates and the
number needed to test
(NNT) to identify 1 asymptomatic infected patient were calculated.
Treatment effectiveness at various time lags since the first positive RT-PCR swab test was measured by rate of events in the experimental arm (EER) and in the control arm (CER), absolute risk increase (ARI) = (EER − CER), and
number needed to treat
(NNT) = (1/ARI).
Total absolute risk reduction for the incidence of new-onset COVID-19 was -0.3% points with an overall relative risk of 0.91 (95% confidence interval, 0.52 to 1.60) and the
number needed to treat
(NNT) was 333 to prevent the incident of one case of COVID-19.