Fig. 5

Challenge region. The challenge region identifies the test sensitivity-specificity combinations for a hypothetical new test, with a similar cost and short-term disutility as CSF biomarkers, that would be cost-effective compared to no test at four levels of pre-test prevalence: 7.5% (black area), 12.7% (dark grey area), 15% (medium grey area), and 30% (light grey area). The test accuracy of CSF biomarkers (white triangle) is also plotted for ease of comparing its test accuracy to the challenge region. (a) Willingness to pay threshold of 50,000 per QALY gained; (b) Willingness to pay threshold of 100,000 per QALY gained. CSF cerebrospinal fluid, WTP Willingness-to-pay, QALY Quality-adjusted life-year