The effect of uncertainty in patient classification on diagnostic performance estimations - Fig 7

(A) Real data from a clinical trial for a new sepsis diagnostic test, conducted over 8 sites in the USA and Netherlands [25]. (B) The apparent performance of the test (y axis) decreases as uncertainty is introduced into the comparator (x axis). 95% confidence intervals are shown. The difference between the apparent test performance at a given comparator misclassification rate and at a comparator misclassification rate of zero indicates the degree of underestimation of true test performance due to uncertainty in the comparator. The vertical lines mark the observed misclassification rates for various patient subsets within the same trial, as described in the text. Misclassification rates are based on quantifying the discordance between independent expert opinions. Solid triangles show the observed measurements for the trial for each of these groups without correction for comparator uncertainty. Sensitivity/PPA and Specificity/NPA are each marked with an asterisk (*) to emphasize that these measures assume no misclassification in the comparator. Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) are the correct terms to use, when the comparator is known to contain uncertainty as in this case.