Journal of Orthodontics | 2021
On the relative performance of diagnostic tests
Abstract
We are continuing with the clinical research scenario previously discussed in the last two parts of this article series (Papageorgiou, 2020, 2021). Briefly, an orthodontist is trying to retrospectively assess the prevalence of gingival recession among patients within a large university clinic using two different diagnostic tests (Papageorgiou, 2020). These two tests have different diagnostic performances, which are summarised in Table 1. However, when applying a diagnostic test to a specific population, it is important to bear in mind that even if its diagnostic performance might remain the same, the prevalence of the disease within the selected sample might vary. Take, as an example, the development of gingival recession on any tooth of the dentition, measured at 15, 18 and 21 years of age. We also want to compare the contribution of orthodontic treatment on the development of gingival recession, so we have two patient groups: (1) one treated orthodontically between 12 and 15 years of age and checked again at 18 and 21 years of age for any recession; and (2) an untreated control group also checked for recession at 15, 18 and 21 years of age. Based on some existing data on this scenario (Renkema et al., 2013), we will assume that the true prevalence of gingival recession for the two patient groups at the corresponding timepoints varies as shown in Table 2. We will also assume the orthodontist is testing 200 treated patients and 200 untreated controls (equally divided with the two tests; each patient tested only once). In this scenario, which of the following statements is correct, if any?