Cost-effectiveness of medical primary prevention strategies to reduce absolute risk of cardiovascular disease in Tanzania: a Markov modelling study

Abstract

Background: Cardiovascular disease (CVD) is a growing cause of mortality and morbidity in Tanzania, but contextualized evidence on cost-effective medical strategies to prevent it is scarce. We aim to perform a cost-effectiveness analysis of medical interventions for primary prevention of CVD using the World Health Organization's (WHO) absolute risk approach for four risk levels.

Methods: The cost-effectiveness analysis was performed from a societal perspective using two Markov decision models: CVD risk without diabetes and CVD risk with diabetes. Primary provider and patient costs were estimated using the ingredients approach and step-down methodologies. Epidemiological data and efficacy inputs were derived from systematic reviews and meta-analyses. We used disability- adjusted life years (DALYs) averted as the outcome measure. Sensitivity analyses were conducted to evaluate the robustness of the model results.

Results: For CVD low-risk patients without diabetes, medical management is not cost-effective unless willingness to pay (WTP) is higher than US$1327 per DALY averted. For moderate-risk patients, WTP must exceed US$164 per DALY before a combination of angiotensin converting enzyme inhibitor (ACEI) and diuretic (Diu) becomes cost-effective, while for high-risk and very high-risk patients the thresholds are US$349 (ACEI, calcium channel blocker (CCB) and Diu) and US$498 per DALY (ACEI, CCB, Diu and Aspirin (ASA)) respectively. For patients with CVD risk with diabetes, a combination of sulfonylureas (Sulf), ACEI and CCB for low and moderate risk (incremental cost-effectiveness ratio (ICER) US$608 and US$115 per DALY respectively), is the most cost-effective, while adding biguanide (Big) to this combination yielded the most favourable ICERs of US$309 and US$350 per DALY for high and very high risk respectively. For the latter, ASA is also part of the combination.

Conclusions: Medical preventive cardiology is very cost-effective for all risk levels except low CVD risk. Budget impact analyses and distributional concerns should be considered further to assess governments' ability and to whom these benefits will accrue.

Keywords: Cardiovascular disease; Cost-effectiveness analysis; Diabetes; Markov modelling; Primary prevention; Societal perspective; Sub-Saharan Africa; Tanzania.

Fig. 1

ICER tornado diagrams for low and very high CVD risk. a Low CVD risk. b Very high CVD risk

Fig. 2

ICER tornado diagrams for low and very high CVD risk with diabetes. a Low CVD risk with diabetes. b Very high CVD risk with diabetes

Fig. 3

Cost-effectiveness acceptability frontier for low and very high CVD risk

Fig. 4

Cost-effectiveness acceptability frontier for low and very high CVD risk with diabetes

Fig. 5

Population EVPI curve for low and very high CVD risk without and with diabetes

Fig. 6

Model structure - CVD primary prevention

Fig. 7

Interventions analysed for each CVD risk level

Fig. 8

Interventions analysed for each CVD with diabetes risk level

Fig. 9

ICER tornado diagrams for moderate and high CVD risk. a Moderate CVD risk. b High CVD risk

Fig. 10

ICER tornado diagrams for moderate and high CVD risk with diabetes. a Moderate CVD risk with diabetes. b High CVD risk with diabetes

Fig. 11

Cost effectiveness acceptability frontier for moderate and high CVD risk

Fig. 12

Cost effectiveness acceptability frontier for moderate and high CVD risk with diabetes