Review of Diagnostic Test Accuracy (DTA) studies in older people.

Diagnostic Test Accuracy (DTA) describes a field of research that aims to assess how well a test is able to detect or exclude a condition of interest. Although geriatric medicine is not as reliant on investigations as other medical disciplines, almost all patient encounters with older adults will involve some form of diagnostic assessment. Thus, understanding the terminology and methods of DTA is essential for any clinician. In this review we use examples based around the diagnosis of dementia to highlight issues in DTA research. Some of these are generic to any DTA research and some are particularly pertinent to older adults. One can apply a test accuracy framework to a clinical question by defining four key components: the condition of interest; the index test(s) (i.e. the assessment(s) of interest); the reference standard (the best available method for assessing the condition of interest) and the population or healthcare setting in which testing takes place. Test accuracy is often described using complementary measures of sensitivity and specificity. However, many other metrics to describe test accuracy are available; in clinical practice predictive values may have greater utility. These and other descriptive statistics can be derived from a two by two table that cross-classifies the index test results with the reference standard results. Test performance and utility is not only determined by accuracy, other measures such as feasibility and acceptability should be considered and may be of particular importance when describing test performance in older adults with physical and cognitive impairments.