For example, we are reviewing an article and the sensitivity of a testing modality 87% while including 50 patients. How we will be able to calculate its upper and lower limit at 95% confidence interval while making a forest-plot?
Sensitivity is, mathematically speaking, a proportion. Thus, the standard method for determining the 95% confidence interval of a proportion applies. However, there are several known nuanced ways of reaching such interval estimate, one of which is Clopper-Pearson exemplified in this link: https://www.medcalc.org/calc/diagnostic_test.php. Wikipedia has a nice overview of the different binomial proportion confidence interval estimation techniques: https://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval.