Sample size
The sample size was based on a target of 150 reference standard positive individuals, for each index test. If the true sensitivity of an index test were 90% or higher, a similar number of positive samples (144) would yield a standard error of the estimate of the sensitivity of ≤2.5%, and a 95% confidence interval width of ±5%. This would have ≥90% power to detect a difference from a level of 80% sensitivity (the level specified as “desired” by the MHRA Target Product Profile [