Thursday, October 01, 2015

Changing epidemiology of rheumatic fever and updated Jones criteria

The American Heart Association has published a new scientific statement on this topic. The changing epidemiology is fascinating and somewhat poorly understood. From the paper:

It is well established that during the 20th century, the incidence of ARF and the prevalence of RHD declined substantially in Europe, North America, and developed nations in other geographic locations…

Although sporadic cases of ARF continue to be seen in affluent nations, the major burden is currently found in low- and middle-income countries and in selected indigenous populations elsewhere. The pattern of disease in the high-prevalence regions is often hyperendemic, with cases occurring throughout the year and a virtual absence of outbreaks. This is in contrast to high-income settings, which experience a low background incidence of ARF with periodic outbreaks.28,43

There is also evidence of differences in incidence even in populations within the same country, which further demonstrates the disproportional disease burden. For example, although the overall mean incidence of ARF in New Zealand rose by 55% over the past 2 decades, the incidence of ARF among the non-Maori/Pacific New Zealand populations declined by 70% over the same period.44 Similar discrepancies in disease burden exist in Australia, where the indigenous population experiences one of the world’s highest reported incidences of ARF at 153 to 380 cases per 100 000 people per year in the 5- to 14-year-old age group,45 whereas in other Australian populations, the incidence approximates European and North American levels.

In summary, the global distribution of ARF/RHD is clearly disproportionate. Certain geographic regions and specific ethnic and socioeconomic groups experience very high rates of ARF incidence, whereas in other regions, the disease has virtually disappeared…

Because the clinical utility of a diagnostic test is determined by a number of factors, including its pretest probability and background disease prevalence, and in view of the heterogeneity in global disease burden noted above, a single set of diagnostic criteria may no longer be sufficient for all population groups and in all geographic regions. To avoid overdiagnosis in low-incidence populations and to avoid underdiagnosis in high-risk populations, variability in applying diagnostic criteria in low-risk compared with high-risk populations is reasonable, as has been promulgated by the Australian rheumatic fever guidelines.

The new criteria would increase the sensitivity. The major change concerns assessment for carditis, in which echocardiography will assume a larger role, in recognition of the improved echocardiographic technology and declining auscultatory skills.

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