Return on investment in needle and syringe programs in Australia: summary report

5. Quality of life (QoL) effects of NSPs

Page last updated: 2002

5.1 Introduction
5.2 Life years gained
5.3 Quality adjusted life years gained

5.1 Introduction

Since both HIV and HCV are potentially life-threatening conditions, one of the main benefits from averting infections is the prevention of premature mortality. In addition, given the natural history of progression of these diseases and its effect on quality of life, significant quality of life benefits may also accrue from the avoidance of HIV and HCV.

The most widely used approach for estimating quality of life benefits in economic evaluations is the quality-adjusted life-year (QALY). In this approach, states of health are assigned a health state preference or 'utility' value, on a scale including 1.0 (full health) and 0 (death). The amount of time an individual spends in a given health state is then multiplied by the health state preference value to calculate the quality-adjusted life-years (QALYs) gained. The main advantage of the QALY approach is that it provides one combined measure of the benefits of a program that both extends life and maintains quality of life.

5.2 Life years gained

The number of life years gained provides a measure of the additional number of years by those persons who would otherwise have been infected with HIV and HCV, but for the effect of NSPs. The effect of NSPs on HIV and HCV is illustrated in Figure 5.1 and Figure 5.2.

The effect of NSPs in terms of life years gained is much greater for HIV than for HCV. The 25,000 persons avoiding HIV are expected to gain an additional 588,000 life years (about 23 years each) than if they had contracted HIV. In comparison, the 21,000 persons avoiding HCV are expected to gain only about 1,200 life years over their lifetime. The difference in these outcomes is essentially due to the different mortality rates associated with each disease and their rate of progression through the various stages.

Figure 5.1 Life years gained for HIV cases avoided

Text equivalent below for Figure 5.1 Life Years Gained for HIV cases avoided
Top of page

Text version of Figure 5.1

Figures in this description are approximate as they have been read from the graph.

Figure 5.1 consists of two graphs.

Life years gained by survivors without HIV increases sharply from 1,000 in 1991 to 27,000 in 2001, before decreasing gradually to 20,000 in 2035 and then decreasing more rapidly to less than 1,000 in 2069.

Life years gained by survivors with HIV increases sharply from 1,000 in 1991 to 26,000 in 2001, before decreasing sharply to 10,000 in 2022 and decreasing gradually to less than 1,000 by 2057.

Figure 5.2 Life years gained for HCV cases avoided

Text equivalent below for Figure 5.2 Life Years Gained for HCV cases avoided

Text version of Figure 5.2

Figures in this description are approximate as they have been read from the graph.Top of page

Figure 5.2 shows two graphs with almost identical shapes.

Life years gained by survivors without HCV increases sharply from 7,000 in 1991 to 21,000 in 2000, before decreasing gradually to 15,000 in 2039 and decreasing sharply to less than 1,000 by 2072.

Life years gained by survivors with HCV increases sharply from 5,000 in 1991 to 21,000 in 2003, before decreasing gradually to 15,000 in 2039 and decreasing sharply to less than 1,000 by 2072.

5.3 Quality adjusted life years gained

The application of an adjustment factor to the number of life years gained to take account of the quality of life effects of these diseases leads to a measure referred to as Quality Adjusted Life Years (QALYs). QALYs gained incorporates both the quantity of life gained, and the quality of life gained by avoiding HIV and HCV. The outcomes of this analysis are presented in Figure 5.3 and Figure 5.4.

The curves "HIV/HCV QALYs Gained" represent the quality adjusted life years for persons who would have had HIV/HCV, but for the effect of NSPs. The gap between these curves and the curves "Life Years Gained" represents the quality effect of HIV and HCV on their lives. The 25,000 persons avoiding HIV are expected to gain an additional 715,000 quality adjusted life years than if they had contracted the disease. In comparison, the 21,000 persons avoiding HCV are expected to gain about 120,000 quality adjusted life years over their lifetime. The difference between the two groups is largely attributable to the greater effect of HIV on the "quantity" of life compared to HCV, rather than the "quality" effect.

Applying the same discount rates used in the financial analysis (viz 5%, 3% and 0%) to QALYs gained results in the figures shown in Table 5.1.

The analysis of the effects of HIV and HCV on both the quantity of life and the quality of life of persons with these diseases adds a further dimension to the assessment of the effect of NSPs among injecting drug users. The benefits demonstrated for consumers in terms of the number of lives saved, the number of life years gained, and the improved quality of life are additional to the direct financial benefits to governments previously identified.

Figure 5.3 Life years and QALYs gained by HIV survivors

Text equivalent below for Figure 5.3 Life Years and QALYs gained by HIV survivors
Top of page

Text version of Figure 5.3

Figures in this description are approximate as they have been read from the graph.

Figure 5.3 consists of two graphs with similar shapes.

Life years gained by HIV survivors increases dramatically from 100 in 1991 to 15,800 in 2033, before decreasing sharply to 1,000 by 2063.

HIV QALYs gained by HIV survivors increases dramatically from 100 in 1991 to 16,800 in 2031, before decreasing sharply to 1,000 by 2063.

Figure 5.4 Life years and QALYs gained by HCV survivors

Text equivalent below for Figure 5.4 Life Years and QALYs gained by HCV survivors
Top of page

Text version of Figure 5.4

Figures in this description are approximate as they have been read from the graph.

Figure 5.4 consists of two graphs.

Life years gained by HCV survivors remains relatively stable at less than 100 for all years between 1991 and 2072.

HIV QALYs gained by HCV survivors increases sharply from 700 in 1991 to 2,200 in 2000, remaining relatively stable until 2036, where it decreases sharply to less than 100 by 2072.

Table 5.1 Net present value (1991) of QALYs gained for HIV and HCV

Discount rateNet Present Value of QALYs gained for HIVNet Present Value of QALYs gained for HCVNet Present Value of QALYs gained for HIV and HCV
5%
138,072
32,207
170,279
3%
248,364
50,041
298,406
0%
715,245
119,992
835,237