A new test is devised to measure the serum level of a specific protein. A sample of blood is taken from a patient, and the new test is performed 3 times with results of 162, 186, and 247 IU/dL. Using the traditional reference test (considered the gold standard), the patient's serum protein level is determined to be 184 IU/dL. A measurement within 5% of the reference test value is considered accurate. Based on these results, the new test most likely has which of the following characteristics?

Question

A new test is devised to measure the serum level of a specific protein.  A sample of blood is taken from a patient, and the new test is performed 3 times with results of 162, 186, and 247 IU/dL.  Using the traditional reference test (considered the gold standard), the patient's serum protein level is determined to be 184 IU/dL.  A measurement within 5% of the reference test value is considered accurate.  Based on these results, the new test most likely has which of the following characteristics?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d31c_8087_bc81_0f9088517c74_MD0003_00 A measurement tool should be both precise and accurate to be useful in the clinical setting. Precision and accuracy are defined as follows: Precision (reliability) is the ability of a test to reproduce identical or similar results with repeat measurements (eg, two bottom figures). Accuracy (validity) is the ability of a test to measure what it is supposed to measure. For a test to be accurate, its results should be equivalent to the results obtained with a gold standard (ie, best conventional test available) on the same individual (eg, two right figures). A precise test gives similar or very close results on repeat measurements. In this example, repeat measurements of the same sample yielded different results (ie, 162, 186, and 247 IU/dL); therefore, the new test has low precision (Choices A and B). The value given by the reference test for the patient is 184 IU/dL, with accurate values considered to be those within 5% of the reference value: Lower cutoff: 184 − (184 × 0.05) = 174.8 Upper cutoff: 184 + (184 × 0.05) = 193.2 Only 1 of the repeat measurements (186 IU/dL) is within 5% of the reference value (range: 174.8-193.2 IU/dL). Therefore, the new test has low accuracy (Choice C). Educational objective: A precise tool is one that consistently provides a very similar or identical value when measuring a fixed quantity. An accurate tool is one that provides a measurement similar to the actual value or within a specified range of a reference value (as reflected by a gold-standard measurement).

A New Test Is Devised to Measure the Serum Level