Background: Medical technologies have traditionally been categorised as either diagnostic tests or interventions and evaluated accordingly. Increasingly assessments of co-dependent technologies are being required, especially in the assessment of targeted therapies. Co-dependent technologies are those where the use of each technology needs to be combined to achieve or enhance the effect of either technology. Assessments of such technologies must consider both the evidence on accuracy of the diagnostic test and the effectiveness of treatment predicted by the test.

Methods: To date, most assessments of co-dependent technologies have involved pharmaceuticals and diagnostic tests. An example is Gefitinib (Iressa) which is used for treatment of locally advanced or metastatic non-small cell lung cancer. Assessments of this pharmaceutical in both the UK and Australia have also included some evaluation of epidermal growth factor receptor (EGFR) testing. This test identifies those patients with a mutation of the EGFR gene and who are likely to respond to Gefitinib.

Results: The primary focus of these assessments has been the effectiveness of Gefitinib in comparison to other treatments—based on accuracy assumptions of the diagnostic test. However, there are numerous testing methodologies that can be employed to determine mutation status in the EGFR gene. The comparative effectiveness of all EGFR tests needs to be assessed as this has implications for the overall effectiveness of Gefitinib. These are issues that have been raised in the assessment of such technologies and requires further development.

Conclusions: An important element in the appraisal of co-dependent technologies is the need to consider the benefits of the joint use of each technology. As such, a challenge in the assessment of co-dependent technologies into the future will be the development of methodological approaches specifically designed to inform the applicability of evidence regarding a given test in tandem with downstream therapeutic performance.