The Youden index is a fairly simple calculation. Add the sensitivity of a diagnostic test to the specificity of the same diagnostic test, then subtract 100 from that value. If the Youden index is not over 50%, then the test does not meet empirical benchmarks for being administered for diagnostic purposes. The Youden index is a measure of a diagnostic test's ability to balance sensitivity (detecting disease) and specificity (detecting health or no disease).
Here is the Youden Index formula:
The cut-off point for having an acceptable Youden index is 50%. Any value below 50% denote an overall lack of the diagnostic test to detect either disease or health.