Table 7.

Pretest Probabilities Required for the Stated Test Accuracies to Impact a Clinical Decision if the Test Result Is Positive or Negative

Sensitivity (%)	Specificity (%)	PrTP to Give PoTP > 65%	PrTP to Give PoTP < 10%
90	90	>17%	<50%
80	80	>32%	<31%
80	40	>58%	<18%

Definition of abbreviations: PoTP = posttest probability; PrTP = pretest probability.

Assuming for a given patient that an aggressive approach will be taken if the posttest probability is greater than 65% and a surveillance approach if the posttest probability is less than 10%, the values listed in the table represent the pretest probabilities required for the stated test accuracies to impact a clinical decision if the test is positive (third column) or negative (fourth column).