Applicability of Receiver Operating Characteristic (ROC) analysis on discrete caries depth ratings

Accuracy of diagnostic tests for caries detection is frequently evaluated by sensitivity and specificity values obtained from data acquired on an ordinal rating scale which classifies lesions according to the depth in enamel and dentin. The interpretation of these parameters may, however, be difficult. Receiver Operating Characteristic (ROC) analysis, on the other hand, yields an expression for overall diagnostic accuracy in a single parameter, facilitating a comparison of performance of several diagnostic tests. The basis for applying ROC analysis has been that data were collected on a confidence (likelihood) scale. The aim of this preliminary study was to investigate whether the application of ROC analysis would yield as valid parameters for diagnostic accuracy in assessment of approximal caries on a depth rating scale as on a likelihood rating scale. The results demonstrated that the accuracy of observer performance was not influenced by the type of rating scale employed, justifying the application of ROC analysis on discrete caries depth ratings.