A quick examination of a test's sensitivity (S), specificity (E) and Youden index can provide useful information as to its usefulness in diagnosis.
Youden index =
= (sensitivity) + (specificity) - 1
Youden |
S |
E |
Interpretation |
<= 0.10 |
NA |
NA |
test of little value |
1.00 |
1.0 |
1.0 |
perfect test, good at any disease prevalence |
>= 0.90 |
NA |
NA |
good test; additional testing may be needed if the prevalence of disease is low |
0.11 to 0.89 |
>= 0.98 |
low |
test good for ruling out a diagnosis if negative (high negative predictive value); need additional testing to exclude false positives |
0.11 to 0.89 |
low |
>= 0.98 |
test good for making a diagnosis if positive (high predictive value); need additional testing to find false negatives |
0.11 to 0.89 |
other |
other |
test performance determined by disease prevalence (the lower the prevalence the worse the performance); multiple tests will be needed to include or exclude a diagnosis |
Purpose: To use a test's sensitivity (S), specificity (E) and Youden index to diagnose a condition.
Objective: other testing
ICD-10: ,