Cost-effectiveness of screening for HIV in primary care: a health economics modelling analysis

Abstract

Background: Early HIV diagnosis reduces morbidity, mortality, the probability of onward transmission, and their associated costs, but might increase cost because of earlier initiation of antiretroviral treatment (ART). We investigated this trade-off by estimating the cost-effectiveness of HIV screening in primary care.

Methods: We modelled the effect of the four-times higher diagnosis rate observed in the intervention arm of the RHIVA2 randomised controlled trial done in Hackney, London (UK), a borough with high HIV prevalence (≥0·2% adult prevalence). We constructed a dynamic, compartmental model representing incidence of infection and the effect of screening for HIV in general practices in Hackney. We assessed cost-effectiveness of the RHIVA2 trial by fitting model diagnosis rates to the trial data, parameterising with epidemiological and behavioural data from the literature when required, using trial testing costs and projecting future costs of treatment.

Findings: Over a 40 year time horizon, incremental cost-effectiveness ratios were £22 201 (95% credible interval 12 662-132 452) per quality-adjusted life-year (QALY) gained, £372 207 (268 162-1 903 385) per death averted, and £628 874 (434 902-4 740 724) per HIV transmission averted. Under this model scenario, with UK cost data, RHIVA2 would reach the upper National Institute for Health and Care Excellence cost-effectiveness threshold (about £30 000 per QALY gained) after 33 years. Scenarios using cost data from Canada (which indicate prolonged and even higher health-care costs for patients diagnosed late) suggest this threshold could be reached in as little as 13 years.

Interpretation: Screening for HIV in primary care has important public health benefits as well as clinical benefits. We predict it to be cost-effective in the UK in the medium term. However, this intervention might be cost-effective far sooner, and even cost-saving, in settings where long-term health-care costs of late-diagnosed patients in high-prevalence regions are much higher (≥60%) than those of patients diagnosed earlier. Screening for HIV in primary care is cost-effective and should be promoted.

Funding: NHS City and Hackney, UK Department of Health, National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care.

Figure 1

Schematic illustrating HIV screening model structure Background death rate is applied to each compartment but, for clarity, is not shown. Numbers refer to stages of HIV infection: 1=acute infection; 2=CD4 count of more than 500 cells per μL; 3=CD4 count of 350–500 cells per μL; 4=CD4 count of 200–349 cells per μL; and 5=CD4 count of less than 200 cells per μL. Diagnosis rate for compartment 1 is assumed to be zero (ie, no diagnoses occur during acute infection). Model assumed diagnosis upon progression to AIDs (appendix p 3).

Figure 2

Outcomes of the RHIVA2 intervention (A) Cumulative QALYs gained as a result of the RHIVA2 trial over time. The intervention is continued for 28 months only (the duration of the RHIVA2 trial). (B) ICER of cost per QALY gained as a result of the RHIVA2 trial, over time, for the three explored scenarios of increased long-term health-care costs for patients diagnosed with late infection. The grey band represents the £20 000–30 000 threshold of cost-effectiveness of interventions used by NICE in the UK. (C) Scenario lines show additional cost of RHIVA2 against QALYs gained, over time, highlighting each 5 year increment since start of the intervention (shown as coloured dots). Shaded grey area represents the NICE threshold of cost-effectiveness. QALY=quality-adjusted life-year. ICER=incremental cost-effectiveness ratio. NICE=National Institute for Health and Care Excellence.

Figure 3

Tornado plot of model parameters varied in univariate sensitivity analysis of scenario 1 Parameters are arranged from widest range of model outcome, with range of model input values shown in parentheses. Dashed line represents ICER estimate for 40 years after RHIVA2 intervention using base case values of all parameters (appendix pp 16–18). Model parameters varied in univariate sensitivity analysis with minimal effect on the ICER (ie, even less than the parameter quality of life multiplier for identified asymptomatic infections, first year) are not shown. ART=antiretroviral therapy. ICER=incremental cost-effectiveness ratio. *Quality of life multiplier.

Figure 4

Model sensitivity to assumptions on change in sexual behaviour after diagnosis, quality of life, and QALY and cost discount rates Scenario analyses exploring the sensitivity of model results to different (A) levels of reduction in sexual behaviour among people upon HIV diagnosis; (B) assumptions regarding quality of life after diagnosis; and (C) QALY and cost discount rates. The NICE threshold for cost-effectiveness of £20 000–30 000 is shown in grey. QALY=quality-adjusted life-year. NICE=National Institute for Health and Care Excellence.