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Cost-effectiveness analysis of hypertension guidelines in South Africa: absolute risk versus blood pressure level

Posted on 01 January 2005

Summary of findings

The study suggest that, in South Africa, guidelines to initiate hypertension treatment based on a blood pressure levels (i.e. BP > 140/90 or 130/85 mm Hg with diabetes mellitus) are more expensive and less effective compared to guidelines based on predicted absolute risk for cardiovascular disease (i.e. 10-year-risk of CVD > 15%) to initiate anti-hypertensive treatment.

Intervention (s)

Two strategies based on blood pressure levels threshold.

Initiate hypertension treatment when:

  • Blood pressure (BP) > 160/95 mm Hg or BP >140/90 mm Hg with diabetes mellitus (1995 Guidelines South Africa).
  • Blood pressure > 140/90 or 130/85 mm Hg with diabetes mellitus (2001 Guidelines South Africa)

Comparator (s)

Four strategies based on absolute risk for cardiovascular disease (CVD).

Initiate hypertension treatment in the following 4 strategies:

  • Individual 10-year-risk of CVD > 15%
  • Individual 10-year-risk of CVD > 20%
  • Individual 10-year-risk of CVD > 30%
  • Individual 10-year-risk of CVD > 40%.

One “No Intervention” strategy in which patient will not receive any pharmacological preventive treatment for hypertension.

Disease classification

Hypertension

Country of the study

South Africa

Time horizon

Lifetime

Discount rate

3% per year applied to both benefit and cost

Source of effectiveness

Two meta-analyses were used to estimate the treatment effect. MacMahon et al. 1990 and Collins et al. 1990.

INSTRUMENT FOR UTILITY MEASURE

Quality adjusted life years - QALYs

Type of cost

Cost related to treatment of hypertension, CVD events and their sequelea were included in the model. Productivity costs were not included. Treatment cost represented wholesale prices and administrations costs.

Source of cost

South Africa cost; when data not available relative weight for individual diagnoses was estimated with US data. These relative differences were applied to average south African CVD administration cost to determine and estimate of each specific CVD admission.  

Currency

US dollar

Modeling approach

Markov Modeling

ICER  (incremental cost-effectiveness ratio)

Initiation of hypertensive treatment at BP > 140/90 mm Hg or BP >130/85 mm Hg with diabetes mellitus was more expensive and less effective than initiation of hypertensive treatment in patient with 10-year-CVD risk >15%.

Initiation of hypertensive treatment at BP > 160/95 mm Hg or BP >140/90 mm Hg with diabetes mellitus was more expensive and less effective than initiation of hypertensive treatment in patient with 10-year-CVD risk >15%.

Initiation of hypertensive treatment with 10 risk score Vs no treatment:

  • 10-year-CVD risk > 40% Vs No treatment ICER = $700/QALY gained
  • 10-year-CVD risk > 30% Vs 10-year-CVD risk > 40% ICER = $1600/QALY gained
  • 10-year-CVD risk >20% Vs 10-year-CVD risk > 30% ICER = $4900/QALY gained
  • 10-year-CVD risk >15% Vs 10-year-CVD risk > 20% ICER = $11000/QALY gained

Sensitivity analysis

Univariate sensitivity analyses; probabilistic multivariate sensitivity analyses with Monte Carlo simulations.

References

Gaziano TA, Steyn K, Cohen DJ, Weinstein MC, Opie LH. Cost-effectiveness analysis of hypertension guidelines in South Africa: absolute risk versus blood pressure level. Circulation. 2005 Dec 6;112(23):3569-76.