Estimating Quality Adjusted Life Years and Willingness to Pay Values for Microbiological Foodborne Disease (Phase 2)

Summary

This project was commissioned by FSA, with support from FSS, to estimate the value of the pain and suffering associated with microbiological foodborne disease (FBD) for the UK using both Quality Adjusted Life Year (QALY) and monetary Willingness to Pay (WTP) metrics.

The geographical scope of the project was the UK. The costs considered were the pain and suffering associated with microbiological foodborne disease (FBD) caused by 10 pathogens. These pathogens were selected as the most material for FSA and FSS in terms of (i) the extent of FBD by the pathogen; (ii) the severity of the FBD and (iii) the cost of the FBD to the UK.

The research used Decision Analytic Models to analyse the flow of people through the various health states which characterise foodborne disease for a set of pathogens using both secondary and primary data. These Decision Analytic Models include short, mild and long term conditions associated with all the modelled pathogens. Decision Analytic Models were used to estimate the QALY burden of selected foodborne pathogens over two time frames, one-year and a life-time. The life-time horizon incorporated the burden of illness as a result of sequelae from the foodborne pathogen.

A stated preference (SP) survey was designed and employed to elicit WTP measures to avoid illness caused by the set of foodborne pathogens. The short term and long term conditions are represented in two forms in parallel approaches: Vignette descriptions and Quality of Life (QoL) survey based on the EuroQol 5 (EQ-5D) dimension, 3 level health questionnaire (EQ5D-3L). The EQ-5D component is one of very few studies which have sought to include a payment vehicle (using WTP) alongside EQ-5D attributes and a duration term. Thus, this study was a test case for this approach. An attraction of such an approach is the possibility of estimating the monetary value of a QALY. 

Key findings from the research were:

The largest QALY burden of illness is attributable to Campylobacter spp. whilst Shigella spp. has the lowest burden. Listeria monocytogenes has the largest burden per case. This is four times the size of the expected burden of the next most severe pathogen Giardia lamblia.

Age-disaggregated analysis indicate that for Campylobacter spp., Norovirus and Salmonella, the age profile of the burden of illness was similar across four age groups (0-4, 5-15, 16-64 and 65+). For VTEC O157 the highest burden was associated with the elderly, followed by children (5-15).

The results indicate that it is possible to successfully implement WTP (Stated Preference) surveys concerning the value of pain and suffering associated with foodborne disease.