Review Question - QID 210448

When the cut-off point of a test is decreased, there will be a decrease in specificity (TN/(TN+FP)) and an increase in sensitivity (TP/(TP+FN)).

Sensitivity and specificity are typically inversely related. In the context of a diagnostic test, moving a cut-off point to identify more patients (usually in the form of decreasing the cutoff value) with the disease increases sensitivity; however, this comes at the expense of decreased specificity, with more false positives occurring. Conversely, minimizing false positives leads to increased specificity at the expense of decreased sensitivity (more false negatives). Ultimately, a cut-off point should be found where a balance is struck between optimal sensitivity and specificity values within a certain clinical context.

Incorrect Answers:
Answer 1: Sensitivity = 90%, specificity = 99% represents a decreased sensitivity and an increased specificity which would be seen if the cutoff was increased rather than decreased.

Answer 2: Sensitivity = 92%, specificity = 97% represents unchanged values. Changing the cutoff values would alter the sensitivity/specificity.

Answer 3: Sensitivity = 95%, specificity = 98% is not a possible change that could occur as both the sensitivity and specificity would not increase with a change in the cutoff value.

Answer 5: Sensitivity = 100%, specificity = 97% is not a possible change because sensitivity likely would not be 100% (only if the cutoff value was 0) and the specificity would decrease if the sensitivity increased.

Bullet Summary:
Increasing the cutoff value for a test would lower the sensitivity and increase the specificity while lowering the cutoff value would increase the sensitivity and decrease the specificity.