Figure 1.

Typical data on the performance of a medical test (D-dimers for venous thromboembolism). Eleven studies on ELISA-based D-dimer assays for the diagnosis of venous thromboembolism.¹⁵ The top panel (a) depicts studies as markers, labeled by author names and thresholds for a positive test (in ng/mL). Studies listed on the left lightly shaded area have a positive likelihood ratio of at least 10. Studies listed on the top lightly shaded area have a negative likelihood ratio of at most 0.1. Studies listed at the intersection of the gray areas (darker gray polygon) have both a positive likelihood ratio of at least 10 and a negative likelihood ratio of 0.1 or less. The second panel (b) shows ‘paired’ forest plots in ascending order of sensitivity (left) along with with the corresponding specificity (right). Note how sensitivity increases with decreasing specificity, which could be explained by a “threshold effect”. The third panel (c) shows the respective negative and positive likelihood ratios.