Intended for healthcare professionals

CCBYNC Open access
Research

# Cost effectiveness of strategies to combat vision and hearing loss in sub-Saharan Africa and South East Asia: mathematical modelling study

BMJ 2012; 344 (Published 02 March 2012) Cite this as: BMJ 2012;344:e615
1. Rob Baltussen, senior researcher1,
2. Andrew Smith, honorary professor2
1. 1Department of Primary and Community Care, Radboud University Nijmegen Medical Center, PO Box 9101 6500HB Nijmegen, The Netherlands
2. 2Centre for Disability and Development, London School of Hygiene and Tropical Medicine, London, UK
1. Correspondence to: R Baltussen R.Baltussen{at}elg.umcn.nl
• Accepted 12 October 2011

## Abstract

Objective To determine the relative costs, effects, and cost effectiveness of selected interventions to control cataract, trachoma, refractive error, hearing loss, meningitis and chronic otitis media.

Design Cost effectiveness analysis of or combined strategies for controlling vision and hearing loss by means of a lifetime population model.

Setting Two World Health Organization sub-regions of the world where vision and hearing loss are major burdens: sub-Saharan Africa and South East Asia.

Data sources Biological and behavioural parameters from clinical and observational studies and population based surveys. Intervention effects and resource inputs based on published reports, expert opinion, and the WHO-CHOICE database.

### Estimating cost effectiveness

We rank ordered interventions on the basis of their cost effectiveness in a number of standardised steps.14 Firstly, within each disease area, we calculated the average cost effectiveness ratios for every intervention by dividing its total number of DALYs averted by its total costs. Secondly, again within each disease area, we considered only those interventions that were both more effective and less costly than other interventions. We then calculated the incremental cost effectiveness ratio for those resulting interventions by dividing the incremental costs by the incremental health effects. The economic attractiveness of an intervention within its disease area is reflected by this incremental cost effectiveness ratio: the lower the incremental cost per DALY averted, the more economically attractive an intervention is. Thirdly, we compared resulting interventions across disease areas on the basis of their incremental cost effectiveness ratios and ranked them accordingly. The interventions with the lowest incremental cost effectiveness ratio are ranked highest and are economically most attractive.

WHO-CHOICE defines interventions that have an incremental cost effectiveness ratio of less than the gross domestic product (GDP) per capita as very cost effective, and those with a ratio less than three times the GDP per capita as cost effective. The regions studied here have a GDP of around $Int2000 per capita,30 which means that interventions costing <$Int2000 per DALY averted can be considered very cost effective and those costing between $Int2000 and$Int6000 can be considered cost effective. Other interventions are considered not cost effective.

### Uncertainty analysis

All interventions are imbued with a certain degree of uncertainty. To handle this aspect of reporting for such a wide range of interventions, we classified interventions according to their degree of cost effectiveness (not cost effective, cost effective, or very cost effective) in order to ascertain order of magnitude differences in cost effectiveness. In addition, we undertook a probabilistic uncertainty analysis using MCLeague software31 to assess the impact of alternative assumptions on costs and effects (which were each varied with plus and minus 25% of their baseline values) on the classification of interventions.

A few modifications were made to previously published analyses.9 10 11 12 Firstly, interventions were considered during the 10 year period 2005to 2015 rather than the period 2000–10, and costs were reported at price levels for year 2005 instead of 2000. Secondly, because of variations in the reporting of coverage levels in previous studies, interventions were evaluated at standardised geographic coverage levels of 50%, 80%, and 95%. Thirdly, assumptions on screening, patient, training, and intervention programme costs were revisited to make results consistent across the analysis. For example, recent price reductions of azithromycin after patent expiry were included in the analysis on trachoma control.

## Results

Following the stepwise approach to the rank ordering of interventions on the basis of their cost effectiveness, we first report the average cost effectiveness ratios of all interventions within each disease area (appendix table B1 on bmj.com).

Second, we report the incremental cost effectiveness ratios for those interventions that both cost less and provide more health effects than other interventions, and these indicate the economic attractiveness of interventions within each disease area (same table).

In trachoma control, trichiasis surgery is the most cost effective intervention, followed by mass treatment with azithromycin in both regions. Both mass treatment with tetracycline ointment and targeted treatment with azithromycin are not cost effective. In cataract control, extracapsular cataract surgery dominates intracapsular surgery in both regions. In both regions, passive screening of children and adults for hearing disorders (in combination with provision of hearing aids) is most cost effective, followed by screening of adults every five years and annual screening of primary and secondary school children. Screening of adults every 10 years is not cost effective. For treatment of chronic otitis media, treatment with topical antibiotics is the most cost effective intervention in both regions. For screening for refractive error (including the provision of spectacles), screening of all primary and secondary school children is most cost effective in sub-Saharan Africa. In South East Asia, screening of secondary school children is most cost effective, followed by screening of both primary and secondary school children.

In a third step, we rank interventions according to their incremental cost effectiveness ratio across all disease areas (tables 4 and 5 for sub-Saharan Africa and South East Asia). This is illustrated in the figure for sub-Saharan Africa. Implementation of all cost effective interventions would cost around $Int19 per capita in sub-Saharan Africa. Incremental cost effectiveness ratios and cumulative cost per capita ($Int) of interventions to combat vision and hearing loss in WHO sub-Saharan African sub-region AfrE. Cost per DALY averted (bars) ranges from very cost effective (such as treatment of chronic otitis media with topical antibiotics at 50% coverage (COM-2) costing $Int16 per DALY averted) to least cost effective (annual screening of schoolchildren and screening of adults every five years for hearing loss (HEA-35) costing$Int3639 per DALY averted). Cumulative cost per capita (dashed line) shows cost if interventions are implemented in order of decreasing economic attractiveness. In case only COM-2 is implemented, cost per capita is $Int0.01. If all shown interventions are implemented, costs per capita increase to$Int14.86. See table 4 for descriptions of the intervention codes

Table 4

Cost effectiveness of strategies to combat vision and hearing loss in WHO sub-Saharan African sub-region AfrE

View this table:
Table 5

Cost effectiveness of strategies to combat vision and hearing loss in WHO South East Asian sub-region SearD

View this table:

### Strengths and limitations

The analysis has several limitations. Firstly, we performed our analysis at the regional level, but important differences in costs or effectiveness of interventions may exist between countries in the same region. Since decision making is made at the country (as opposed to regional) level, more refined estimates of costs, effects, and cost effectiveness should be made at the country level, based on country-specific data. A good example is the contextualisation of WHO-CHOICE regional results to the country level in Mexico, as reported in this series.32

Secondly, assumptions on intervention effectiveness are based on a variety of sources and may reflect contexts other than the regions analysed—the same level of effectiveness may not always be realised in reality, and results should be interpreted with caution. Yet, our probabilistic uncertainty analysis indicates that our study results are robust to alternative assumptions. These issues are discussed in detail in previously published papers.9 10 11 12

Thirdly, we did not evaluate all possible interventions that could reduce vision or hearing loss, and our choice of interventions is somewhat arbitrary. Policymakers should be aware of this, and should not limit their choice of interventions to those included in this analysis.

Fourthly, and more specifically, we evaluated screening for hearing disorders as carried out by trained primary health workers (incurring healthcare costs), and screening for refractive error as carried out by trained school teachers (who incur no healthcare costs). However, alternative assumptions have only limited impact on study results.

Fifthly, in the absence of reliable data, we did not include time costs of people seeking and undergoing care, nor did we include changes in productivity losses as a result of the interventions. The perspective of analysis is therefore not truly societal. Inclusion of productivity gains after reductions in vision and hearing loss would render the interventions more cost effective.

Sixthly, we assumed that all interventions were implemented at a relatively high efficiency level—which allows an equal comparison between the cost effectiveness of interventions and avoids the complications from interventions that were not implemented well would be disadvantaged in comparison with those that were well implemented.

Lastly, the analysis evaluates interventions at 50%, 80%, and 95% geographic coverage levels, following standardised WHO-CHOICE methodology. The higher coverage levels may not always be achievable but are included to indicate the economies of scale that may take place when more people are reached with an intervention.23

The above limitations should be considered in the overall aim of WHO-CHOICE analysis to provide broad indications on the cost effectiveness of a range of interventions to inform general policy discussions, rather than to deliver precise estimates on a specific intervention.15

Study strengths include the use of disease models that have already been published and applied, consideration of combinations of interventions, use of a generic measure of effectiveness, and testing of important assumptions through sensitivity analyses.

### Comparison with other studies

This study includes a number of modifications in comparison to the previously published analysis. The higher 2005 price levels have generally resulted in higher cost effectiveness ratios, but these and other modifications have generally not changed study conclusions. The exception is mass or targeted treatment with azithromycin in trachoma control, where price reductions of azithromycin have offset general price increases in the period from 2000 to 2005 and have thus rendered the interventions more cost effective.

### Policy implications

Our results have four major policy implications. Firstly, they reinforce the fact that cataract surgery and treatment of chronic otitis media are among the key interventions for combating vision and hearing impairment.

Secondly, they show that there is a strong economic case to consider screening for refractive error among schoolchildren. This supports current efforts within the VISION 2020 initiative to give greater prominence to screening programmes. Screening schoolchildren and adults for hearing disorders is somewhat less cost effective but is still economically attractive according to commonly used benchmarks.

Thirdly, inclusion of mass treatment with azithromycin in programmes to eliminate trachoma needs careful analysis: although the intervention was cost effective in sub-Saharan Africa according to commonly used benchmarks, it was not in South East Asia. However, many programmes around the world use donated azithromycin, which makes the intervention economically more attractive than we have reported here. In our analysis, trichiasis surgery is more cost effective and thus provides better value for money.

Fourth, our results show that substantial health gains can be achieved—up to 32 and 84 million DALYs averted in sub-Saharan Africa and South East Asia respectively, when available effective interventions are scaled up. This will require major resource mobilisation efforts at domestic and international level. Yet, whether such substantial investments are warranted can only be judged when the findings our present study—that vision and hearing impairment control interventions are generally cost effective—are considered in relation to the economic attractiveness of other, existing or new, interventions in health. For this broader analysis, we refer to Evans et al15 and Chisholm et al,33 who compare the economic attractiveness of a wide range of interventions to control, respectively, communicable and non-communicable diseases.

#### What is already known on this topic

• Several studies have reported on the global and regional cost effectiveness of interventions targeting cataract, trachoma, refractive error and different causes of hearing impairment.

• However, studies have been carried out in isolation, which prevents the cost effectiveness of the different interventions in visual and hearing impairment control being directly compared.

• In addition, these studies have been analysed using year 2000 demographics and price levels

• This study directly compares cost and effects of interventions targeting cataract, trachoma, refractive error and different causes of hearing impairment, using more recent price levels in Sub-Saharan Africa and South East Asia

• This allows the identification of most efficient strategies to reduce vision and hearing loss

## Notes

Cite this as: BMJ 2012;344:e615

## Footnotes

• doi: 10.1136/bmj.e586
• , doi: 10.1136/bmj.e609
• , doi: 10.1136/bmj.e612
• , doi: 10.1136/bmj.e607
• , doi: 10.1136/bmj.e355
• , doi: 10.1136/bmj.e608
• , doi: 10.1136/bmj.e614
• Contributors: Both authors contributed to the conception, design and interpretation of data, and drafting of the manuscript. RB performed the technical analysis. Both authors approved the submitted version of the manuscript. RB is the guarantor of the manuscript.

• Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.

• Ethical approval: Ethical approval was not required for this study.

• Data sharing: No additional data available

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.

View Abstract