Table 2.

Case studies of precision medicine.

Diagnostic test and source of heterogeneity	Relevant population and decision	Potential source of value	Challenge when establishing the economic case
Companion diagnostic for activating mutations of epidermal growth factor receptor tyrosine kinase.	To inform the prescribing of gefitinib for patients with non-small cell lung cancer.	Improved clinical effectiveness.	Limited evidence from test result to cost and health outcomes for all diagnostics.
Thiopurine S-methyltransferase mutation genotyping or enzyme phenotyping.	To inform the prescribing of azathioprine for patients with eligible autoimmune diseases.	Reduced adverse drug reactions.	Clinicians may implement testing strategy imperfectly.
Assays to detect anti-drug antibodies and to measure drug levels.	To inform the prescribing of monoclonal antibody tumor necrosis factor-α inhibitors for patients with eligible autoimmune diseases.	Improved health outcomes and/or reduced health care resource use.	Different permutations of multiple tests are possible; Position of tests in care pathway may be uncertain; The cost of novel testing strategies may be unknown.
Next generation sequencing gene panel test.	To inform the diagnosis of inherited retinal dystrophies.	Improved diagnostic accuracy and potentially reduced health care resource use.	Capacity constraints may restrict the number of tests performed; Non-health consequences may be considered by decision-makers.