An ultrasound evaluation of the extracranial portion of the internal carotid artery can predict significant ( 70%) angiographic stenosis with a sensitivity of 100% and a specificity of 72%. When this test is applied to a large population of patients with multiple cardiovascular risk factors, which of the following test parameters is expected to be closest to 100%?

Question

An ultrasound evaluation of the extracranial portion of the internal carotid artery can predict significant (> 70%) angiographic stenosis with a sensitivity of 100% and a specificity of 72%.  When this test is applied to a large population of patients with multiple cardiovascular risk factors, which of the following test parameters is expected to be closest to 100%?

Quizplus · Accepted Answer

11ec193a_9730_86a2_853d_c13daaea3377_MD0002_00 Sensitivity is the probability that a patient with a given disease will test positive for the disease. Tests with high sensitivity can better rule out a disease (SnOUT). Specificity is the probability that a patient without a given disease will test negative for the disease. Tests with high specificity can better rule in a disease (SpIN). It is important to have high sensitivity for screening tests, while confirmatory tests should have high specificity. Positive predictive value (PPV) is the probability that a positive test result correctly identifies an individual who actually has the disease. A higher specificity leads to fewer false positives and increases the PPV of the test (Choice D). Negative predictive value (NPV) is the probability that a negative test result correctly identifies an individual who does not have the disease. A higher sensitivity leads to fewer false negatives and increases the NPV of the test. In this case, the test has a 100% sensitivity, implying no false negatives and a NPV value of 100%. (Choice A) Validity (accuracy) is defined as the test's ability to measure what it is supposed to measure. For a binary classification test, it is a measure of how well the test correctly identifies or excludes a condition. In other words, accuracy is the proportion of true results (both true positives and true negatives) in the population and is calculated as (TP + TN) / (TP + FP + FN + TN). (Choice B) The false discovery rate (FDR) is the expected proportion of false discoveries (type I errors) among all statistically significant discoveries (rejected null hypotheses) during simultaneous testing of multiple hypotheses. FDR correction methods are designed to reduce the proportion of incorrectly rejected null hypotheses (false discoveries) while maintaining acceptable statistical power. (Choice E) A reliable test is reproducible; that is, it gives similar or very close results on repeat measurements. Reliability (precision) is typically quantified in terms of the coefficient of variation (CV). The CV is the standard deviation of the set of repeated measurements divided by their mean and is generally expressed as a percentage. The smaller the CV, the more reliable the test. Educational objective: Screening tests should have high sensitivity (SnOUT) while confirmatory tests should have high specificity (SpIN). As the sensitivity increases, the number of false negatives decreases and the negative predictive value increases. Similarly, as the specificity increases, the number of false positives decreases and the positive predictive value increases. __________

An Ultrasound Evaluation of the Extracranial Portion of the Internal