A paper in the RHD special issue of Global Heart, the journal of the World Heart Federation, analyses the burden of disease and suggests that numbers published to date (ranging from at least 233,000 deaths per year upwards) could be substantial underestimates for a variety of reasons, most commonly lack of high quality (or in some cases any) data from high-prevalence countries and regions. The paper is by Dr Liesl Zühlke, University of Cape Town and Red Cross War Memorial Children's Hospital, Cape Town, South Africa and Dr Andrew Steer, Centre for International Child Health at the University of Melbourne, Australia.
The authors say: "Currently available figures used to define the global burden of acute rheumatic fever and rheumatic heart disease, although crucial to control efforts, are imperfect. Data have been hindered by methodological differences between studies, by patchy coverage within countries and across regions, and by an incomplete understanding of the relationship between echocardiographic detection of asymptomatic mild disease and progression to symptomatic disease."
A WHO study published in 2005 found an overall global burden of 471,000 annual cases of ARF, with the incidence of acute rheumatic fever (ARF) ranging from 10 cases per 100,000 children aged 5 to 15 years in industrialised countries to 374 cases per 100,000 in the Pacific region. The overall burden of RHD was estimated to be 15.6 million prevalent cases with 282,000 new cases and over 233,000 deaths per year.
The recently published Global Burden of Disease Study reports that the number of years lived with disability (YLD) due to RHD was estimated in 2010 at 1 430 000*, equivalent to a quarter of the figure for all cancers combined. Lozarno and colleagues reported 345,100 deaths due to RHD in 2010 which represents a 25% reduction compared to 1990; with an age-standardised death rate of 5.2 per 100,000 which was a 53% reduction compared to1990. However, the authors caution that these figures should be viewed with caution and are currently being re-analysed for the next Global Burden of Disease analysis in 2014.
RHD burden of disease estimates also face the new problem of both more definite and borderline cases being diagnosed with echocardiogram equipment. The authors say: "It is perhaps time to change the way that we think about RHD and attempt to describe the disease burden with greater subtlety that takes into account our increasing understanding of the disease." Such a revised model might include an assessment of RHD burden in two categories: 1) Symptomatic disease which could also be called active disease; and 2) Asymptomatic disease which could also be called latent disease This approach has some similarities (but also obvious differences) to the model of disease applied to other latent diseases including infection with Mycobacterium tuberculosis.
The authors conclude: "Moving forward, it will be critical to generate high quality and comprehensive data regarding all aspects of the burden of ARF and RHD to better inform national, regional and global control strategies... New studies are underway in several high-prevalence sentinel areas in diverse geographic locations to address the need of contemporary data... These data will provide vital information in order to advocate even more strongly for directed funding and public health interventions to control ARF and RHD."
Note to editors: As a comparison, YLD for ischaemic heart disease in 2010 was 8 795 000, showing that RHD is causing a substantial burden of disease globally. As discussed, the YLD for RHD, at 1 430 000, is likely to be a substantial underestimate.
Journal
Global Heart