DEFINING DISEASE TYPES I, II AND III - WHO

1 1 Background document provided by the WHO Secretariat 14 November 2012 DEFINING DISEASE TYPES I, II AND III The CEWG was tasked with framing its analysis around DISEASE TYPES that were first introduced by the Commission on Macroeconomics and Health and elaborated in the report of the Commission on Intellectual Property Rights, Innovation and Public Health. The definition of diseases into TYPES mixes a number of concepts together including the wealth of a country between rich and poor; the state of its development between developed and developing and most importantly a measure of the burden of diseases by the incidence of the DISEASE within the population.

2 The definitions themselves are combined such that: Type I diseases: are incident in both rich and poor countries, with large numbers of vulnerable populations in each. Type II diseases: are incident in both rich and poor countries, but with a substantial proportion of the cases in poor countries. Type III diseases: are those that are overwhelmingly or exclusively incident in developing countries. In addition the CEWG analysis for Type I diseases was to focus on the R&D needs specific to developing countries.

3 While often quoted these DISEASE Type definitions have never been mapped against a full range of diseases, instead examples in each Type have been highlighted. For example cancer is a typical Type I DISEASE , TB and AIDs being typical of Type II with Type III diseases broadly corresponding to the infectious tropical diseases such as leishmaniasis or malaria. However, if greater efforts are to be made to map resource flows for R&D against these DISEASE TYPES then an approach for classifying them needs to be developed and agreed.

4 As a starting point the WHO Global Burden of Diseases report, last published in 2004 and due to be updated with data up to 2010, provides an accepted list of DISEASE causes that can be used at a global level for this type of analysis. The next category within the original definition is wealth and/or the stage of development of a country. While in common usage there is no agreed UN convention that defines all countries between developed and developing. Therefore, an objective alternative is to use the income categories calculated by the World Bank.

5 Finally measuring DISEASE incidence is only one element of DISEASE burden whereas the Disability Adjusted Life Years (DALYs) seeks to bring together a range of measures that, when combined with population size, can be used to give an estimate of the DISEASE burden at a national, regional or even global level. In order to inform discussion at the Open Ended Member States meeting 26th-28th November a working list of diseases was generated using a combination of the measures cited above. 2 The approach involved using the conditions/diseases presented in the 2004 Global Burden of Diseases report.

6 The DALYs for each DISEASE per 100,000 population was aggregated and a total for each DISEASE cause was obtained for low and middle income countries combined to enable a comparison with the total DALYs per 100,000 population per DISEASE for high income countries. A ratio was then calculated comparing the DALY figure between the low/middle income countries with the high income countries. These ratios were then ranked high to low where a ratio of means the DISEASE is found in equal measure in all countries which is analogous to the concept of a Type I DISEASE .

7 Looking at this ranking table diseases were then subjectively categorised using the following range of ratio figures where this created recognisable groups that aligned with an understanding of what the DISEASE TYPES were aiming to represent where (Table 1): Type I: - < the DISEASE burden is approximately the same and no more than 3 times higher in low/middle income countries than high income countries. Type II: > < the DISEASE burden is at a rate that is between times higher in low/middle income countries than in a high income country.

8 Type III: > the DISEASE burden is at a rate that is at least times and up to more than a 1000 times higher than is recorded in high income countries. It is to be stressed this approach is not intended to be prescriptive but enables a categorization of diseases to be generated in a transparent manner that can then form the basis for discussion and further analysis. So, for example, the exact boundary between the DISEASE TYPES is not an exact figure and only suggested here. There is no simple metric that combines the socio-economic and public health data inherent in the original Commission definitions and it is recognised that there are a number of limitations in this approach.

9 For example the figures used are crude aggregates and not age-weighted for population size so, for example, colon cancer will have a higher measure of prevalence in high income countries due to the older age of those populations. The DALYs measure itself is often an estimate where accurate DISEASE figures (incidence, mortality etc.) are not available, which is often a challenge for low income countries. The advantages or this approach are that it is a relatively simple method that can be developed using publically available data to produce a categorization of DISEASE TYPES to inform debates on the scope of any R&D monitoring activities.

10 The method is offered here as a tool that can be adapted or discarded to suit one s needs. It is also a dynamic measure that can change over time and can be adapted for use at a national, sub-national or regional level. For example the diseases in the Type categories will vary greatly between individual countries and over time; a concept that was envisioned by the Commission in the original definition. At this high level the classification of Type II and III diseases are relatively uncontested, even if the boundary between them might be raised up or down, and this method supports the general consensus.