Figure 1.

Likelihood ratio (LR) graph: regions of comparison ²⁷. The slopes (tangents) of the lines connecting the cutoff point of a 'gold standard' comparator test to points (0, 0) and (100, 100) represent the LR+ and the LR−, respectively. The LR+ and LR− lines divide the chart into four areas. Depending on the position of a competitor test in these areas, it can be defined as overall superior to the gold standard, overall inferior, superior for confirming the absence of the disease under investigation, or superior for confirming the presence of the same disease. Youden's index (j) is the intercept on the vertical axis of a line whose slope is 1, passing through the cutoff point.