Table 3: Frequencies of mutation detection in the per-protocol study population.

Test resultGold standard test#Total
Mutation presentMutation absent

Reference lab: mutation present3142316
Reference lab: mutation absent0685685

Excluded the 2 individuals in whom switch of DNA samples was discovered before counter-expertise test had been performed (subjects A and B from Figure 1 and Table 2).
#Gold standard test is defined as the overall conclusion after following the steps for mutation analysis in both the reference laboratory and the counter-expertise laboratory.
Overall accuracy = 999/1001 = 0.998, 95%. Confidence interval: to to 1.00.
Sensitivity = 314/314 = 1.0, 95%. Confidence interval: to .
Specificity = 685/687 = 0.997, 95%. Confidence interval: to to 1.00.
Likelihood ratio for a positive test = sensitivity/(1 − specificity) = 344, indicating that a positive result is 344 times more likely to occur in someone with the mutation according to the gold standard than in one without it.