A 30-year-old woman comes to the physician after finding a breast mass on self examination. After the appropriate workup, the physician decides to proceed with fine-needle aspiration (FNA). Cytology of the aspirate comes back negative for malignancy. However, the patient is still concerned about the possibility of breast cancer despite her negative FNA result. Which of the following test parameters would be the most helpful for determining this patient's residual risk of breast cancer?

Question

A 30-year-old woman comes to the physician after finding a breast mass on self examination.  After the appropriate workup, the physician decides to proceed with fine-needle aspiration (FNA).  Cytology of the aspirate comes back negative for malignancy.  However, the patient is still concerned about the possibility of breast cancer despite her negative FNA result.  Which of the following test parameters would be the most helpful for determining this patient's residual risk of breast cancer?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c102_a867_8f63_9bc5802c744e_MD0005_00 The negative predictive value (NPV) is the probability of not having a disease given a negative test result. The patient in this scenario tested negative; therefore, NPV gives the probability that she is actually disease-free. Her probability of still having breast cancer is given by 1 - NPV (the false omission rate). Positive and negative predictive values are dependent on the prevalence of the disease in the tested population. They can only be applied to individuals if the pre-test probability of the disease is known. In this example, if the pre-test probability of breast cancer is high after initial workup (and the FNA result is negative), then the NPV will be relatively low. On the other hand, if the pre-test probability of breast cancer is low after initial workup, then the NPV will be higher. (Choice B) Positive predictive value follows the same concept but applies only if the test returns positive. (Choices C and D) Sensitivity and specificity are intrinsic test parameters that are not affected by disease prevalence. Even though a negative result on a maximally sensitive test (100%) would effectively rule out the disease, very few diagnostic tests are 100% sensitive. Therefore, the NPV would be more beneficial for determining this patient's residual breast cancer risk. (Choice E) Validity (accuracy) is a parameter used to assess the appropriateness of a diagnostic test (ie, that the test measures what it is supposed to measure). Validity is a measure of the overall usefulness of a test, but predictive values are better suited for determining the value of a single positive or negative test result. Educational objective: The negative predictive value is the probability of being disease free given a negative test result. The pre-test probability of disease (eg, disease prevalence) must be known to calculate positive and negative predictive values.

A 30-Year-Old Woman Comes to the Physician After Finding a Breast