Sensitivity and Specificity
The majority of studies which have evaluated the diagnostic accuracy of dermoscopy have relied on calculation of specificity and sensitivity, by comparing the diagnosis made by dermoscopy with the histopathological diagnosis.
- Specificity: the proportion of benign pigmented skin lesions that are correctly identified by dermoscopy
- Sensitivity: the proportion of melanomas that are correctly identified by dermoscopy
Advantages and Disadvantages
- Valid indicators of diagnostic test performance
- Easily understood
The diagnosis made by dermoscopy has to be divided into two groups: benign and malignant. This is surely an oversimplification of the diagnostic procedure of dermoscopy.
Dermoscopy is a tool to minimize uncertainty, thus aiming to the correct interpretation of a dermoscopic finding and leading to a decision of the necessity of further diagnostic procedures (excision). However, the interpretation of the dermoscopic findings is also influenced by other variables:
- Clinical impression of the lesion
- Age of the patient
- Anatomic side
- Number and appearance of other lesions on the same patient
Other disadvantages to the evaluation of diagnostic tests by their sensitivity and specificity include the prevalence of the disease of interest (in this case melanoma) not being taken into account, and the difficulties of comparing two diagnostic tests.