The American Diabetes Association (ADA) recently lowered the cut off value for fasting glucose used in diagnosing diabetes mellitus from 140 mg/dL to 126 mg/dL. This reference interval change would be expected to produce which of the following alterations?
Decrease the test's sensitivity
Increase the test's false negative rate
Increase the test's negative predictive value
Increase the test's positive predictive value
The negative predictive value of a test (PV-) refers to the percent chance that a normal test result is a true negative (TN; a healthy person with a normal test result) rather than a false negative (FN; a diseased person with a normal test result). It is expressed by the following formula: PV- = TN/(TN + FN) Similarly, the positive predictive value of a test (PV+) reflects the probability that an abnormal test result represents a true positive (TP) rather than a FP (a TP is an abnormal test result in an individual with disease, while a FP is an abnormal test result in a healthy person). PV+ is calculated using the following formula :PV+ = TP/(TP + FP)