Defining 'optimal' test cut-off using global test metrics: evidence from a cognitive screening instrument

摘要

Aim:To examine the variation of several global metrics of test accuracy with test cut-off for the diagnosis of dementia. These metrics included some based on the receiver operating characteristic curve, such as Youden index, and some independent of receiver operating characteristic curve, such as correct classification accuracy.Materials & methods:Data from a test accuracy study of Mini-Addenbrooke's Cognitive Examination were used to calculate and plot each global measure against test cut-off.Results:Different 'optimal' cut-points were identified for the different global measures, with a spread of ten points in observed optimal cut-off in the 30-point Mini-Addenbrooke's Cognitive Examination scale. Using these optima gave a large variation in test sensitivity from very high (diagnostic odds ratio) to very low (likelihood to be diagnosed or misdiagnosed), but all had high negative predictive value.Conclusion:The method used to determine the cut-off of cognitive screening instruments may have significant implications for test performance.