Evaluating Interventions to Improve Antiretroviral Adherence- How Much of an Effect Is Required for Favorable Value?

Objective

Uncertainty about the value of antiretroviral therapy (ARV) adherence interventions may be a barrier to implementation and evaluation. Our objective is to estimate the minimum effectiveness required for ARV adherence interventions to deliver acceptable value.

Methods

We used a validated HIV computer simulation to estimate the impact of ARV adherence interventions on incremental costs and life expectancy. Across a wide range of intervention costs ($1000–10,000, one time or per year), we estimated the smallest effect size compatible with acceptable value (incremental cost-effective ratio ≤$100,000 per life-year). Effect sizes were measured using relative risk (RR) and absolute risk reduction (ARR), and these metrics were applied to nonadherence and nonadherence risk factors. Costs were estimated from a societal perspective ($2003) discounted at 3%.

Results

To give acceptable value, a one-time $1000 intervention must reduce ARV nonadherence by RR ≤ 0.82 (ARR ≥ 0.04) for moderately nonadherent patients (20% of ARV doses missed) and RR ≤ 0.90 (ARR ≥ 0.05) for severely nonadherent patients (50% of ARV doses missed). A one-time $5000 intervention has an unacceptable value regardless of effect size for moderately nonadherent patients, and must reduce ARV nonadherence by RR ≤ 0.31 (ARR ≥ 0.69) for severely nonadherent patients. Interventions aimed at behavioral risk factors (e.g., unhealthy alcohol use) may confer acceptable value (e.g., if ≤$2000 and effect RR ≤ 0.71 [ARR ≥ 0.29]).

Conclusions

ARV adherence interventions with plausible effect sizes may offer favorable value if they cost $5000 one time or per year. ARV adherence interventions with a favorable value should become more integral components of HIV care.