Plan a diagnostic study to estimate both sensitivity and specificity. Prevalence is explicit because it determines how many diseased and non-diseased participants a total sample is expected to contain. Choose the Buderer (1996) normal approximation, Wilson score interval width, or exact Clopper–Pearson interval width.
For Wilson/exact planning, the expected positive count is rounded at each candidate group size and the smallest qualifying diseased/non-diseased count is found. Final total N is increased until both counts are available at the stated prevalence.