Diagnostic Studies in Surgery

Making a surgical diagnosis is an important first step in clinical management. Using the example of diagnostic tests on a thyroid nodule, a literature search identified an article in which the TIRADS (Thyroid Imaging Reporting and Data System) for Ultrasound (US) features of thyroid nodule was followed by US-guided fine-needle aspiration cytology (FNAB) reported by the Bethesda System for reporting thyroid cytopathology. From these two tests, the Likelihood Ratio (LR), its interpretation, and its usefulness in sequenced tests to refine the diagnosis are emphasized. In this case, the pretest probability (prevalence) of cancer of 3% was increased to 6.7% using TlRADS (LR = 2.34) and further increased to 12.4% using the Bethesda System (LR = 1.97). A strategy to determine whether the test results in an article are valid, what the LRs are, and whether the results will help in caring for your patient is presented.