A new portable cholesterol-measuring device is being developed for use in medically underserved communities. During clinical trials of an early prototype, a patient's cholesterol level is found to be 200 mg/dL, 201 mg/dL, and 200 mg/dL on 3 separate measurements of the same blood sample. Using the gold standard measurement method, the same sample is found to have a cholesterol level of 260 mg/dL. Which of the following descriptions best characterizes the new cholesterol-measuring device?

Question

A new portable cholesterol-measuring device is being developed for use in medically underserved communities.  During clinical trials of an early prototype, a patient's cholesterol level is found to be 200 mg/dL, 201 mg/dL, and 200 mg/dL on 3 separate measurements of the same blood sample.  Using the gold standard measurement method, the same sample is found to have a cholesterol level of 260 mg/dL.  Which of the following descriptions best characterizes the new cholesterol-measuring device?

Quizplus · Accepted Answer

11ec160b_36fa_a53a_9249_390ca8a50736_MD0001_00 Precision (reliability) is the ability of a test to reproduce identical or similar results with repeated measurements (bottom half of figure). Accuracy (validity) is the ability of a test to measure what it is supposed to measure. For a new test to be accurate, its results should be equivalent to the results obtained with a gold standard (eg, best conventional test available) on the same individual (right half of figure). In this case, repeated measurements of the same blood sample yielded nearly identical values; therefore, the new device has high precision. However, none of the measurements with the new device were equivalent to the results obtained with the gold standard (ie, the measurements are incorrect), meaning the new device has low accuracy. (Choices C and F) Sensitivity is defined as the percentage of diseased individuals who are correctly identified (ie, proportion of subjects who have a positive test among all those with disease), whereas specificity is defined as the percentage of healthy individuals who are correctly identified (ie, proportion of subjects who have a negative test among all those without disease). Poor accuracy or precision can lead to low test sensitivity and specificity. However, no information is provided to determine the sensitivity or specificity of the new device compared to the gold standard test. Educational objective: A precise tool is one that consistently provides very similar or the same value when measuring a fixed quantity. An accurate tool is one that provides a measurement identical or similar to the actual value (as reflected in a gold standard measurement).

A New Portable Cholesterol-Measuring Device Is Being Developed for Use