Introduction.

In this article, a new global performance index of a diagnostic test is proposed: the T Index, which corresponds to the proportion of the hit ratio (Hr) minus the error ratio (Er) divided by the hit ratio (Hr).

Methods.

To describe the theoretical and practical foundations of the T index; to compare the T index against the Youden index in order to establish whether two or more diagnostic modalities differ in their ability to correctly discriminate between truly ill and healthy individuals; and to compare the T index with the Youden index in order to establish whether the T index can be used to choose the “best cut-off point” when the diagnostic test of interest expresses its results in a continuous quantitative way.

Results.

Compared with the Youden index, the T index allows us to differentiate between diagnostic tests with high diagnostic performance and those with poor diagnostic performance. In addition, the T index, reliably, allows choosing “the best cut-off point” when a diagnostic test uses a continuous quantitative variable to express its results.

Conclusions.

By contrasting the results of the T index versus the Youden index and the results of the T index versus the COR curve, we can affirm that the T index is an accurate and efficient index.

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