Modelling technique, structural assumptions, input parameter values: which has the most impact on the results of a cost-effectiveness analysis?

Disparities in model-based cost-effectiveness analyses of tuberculosis diagnosis: A systematic review

Background

Structural approach disparities were minimally addressed in past systematic reviews of model-based cost-effectiveness analyses addressing Tuberculosis management strategies. This review aimed to identify the structural approach disparities in model-based cost-effectiveness analysis studies addressing Tuberculosis diagnosis and describe potential hazards caused by those disparities.

Methods

A systematic search to identify studies published before October 2015 was performed in five electronic databases. After removal of duplication, studies’ titles and abstracts were screened based on predetermined criteria. The full texts of potentially relevant studies were subsequently screened and excluded when they did not address active pulmonary Tuberculosis diagnosis. Quality of the studies was assessed using the “Philips’ checklist.” Various data regarding general information, cost-effectiveness results, and disease modeling were extracted using standardized data extraction forms. Data pertaining to models’ structural approaches were compared and analyzed qualitatively for their applicability in various study settings, as well as their potential influence on main outcomes and cost-effectiveness conclusion.

Results

A total of 27 studies were included in the review. Most studies utilized a static model, which could underestimate the cost-effectiveness of the diagnostic tools strategies, due to the omission of indirect diagnosis effects, i.e. transmission reduction. A few structural assumption disparities were found in the dynamic models. Extensive disparities were found in the static models, consisting of varying structural assumptions regarding treatment outcomes, clinical diagnosis and empirical treatment, inpatient discharge decision, and re-diagnosis of false negative patients.

Conclusion

In cost-effectiveness analysis studies addressing active pulmonary Tuberculosis diagnosis, models showed numerous disparities in their structural approaches. Several structural approaches could be inapplicable in certain settings. Furthermore, they could contribute to under- or overestimation of the cost-effectiveness of the diagnosis tools or strategies. They could thus lead to ambiguities and difficulties when interpreting a study result. A set of recommendations is proposed to manage issues related to these structural disparities.

Cost-Effectiveness Models in Age-Related Macular Degeneration: Issues and Challenges

Age-related macular degeneration (AMD) is a common ophthalmic condition that can have few symptoms in its early stage but can progress to major visual impairment. While there are no treatments for early-stage AMD, there are multiple modalities of treatment for advanced disease. Given the increasing prevalence of the disease, there are dozens of analyses of cost effectiveness of AMD treatments, but methods and approaches vary broadly. The goal of this review was to identify, characterize, and critique published models in AMD and provide guidance for their interpretation. After a literature review was performed to identify studies, and exclusion criteria applied to limit the review to studies comparing treatments for AMD, we compared methods across the 36 studies meeting the review criteria. To some extent, variation was related to targeting different audiences or acknowledging the most appropriate population for a given treatment. However, the review identified potential areas of uncertainty and difficulty in interpretation, particularly regarding duration of observation periods and the importance of visual acuity as an endpoint or a proxy for patient-reported utilities. We urge thoughtful consideration of these study characteristics when comparing results.