J37 Prevalence Of Huntington Disease In Navarra (spain). Sensitivity And Positive Predictive Value Of Different Sources Of Asecertaiment

Abstract

Background Huntington disease (HD) is a rare disease that occurs worldwide but shows large geographic differences in its prevalence. Few epidemiological studies have been carried out in Spain where the prevalence of HD is uncertain. Aims To provide accurate estimates of the overall prevalence and population at risk for HD in Navarra (Spain) and to asses the sensitivity and the positive predictive value (PPV) of multisource ascertainment. Methods Patients were identified through the Primary Care and Hospital (CMBD coding at hospital discharge) databases, and the Medical Genetics Department. HD cases were defined as individuals with motor or neurocognitive symptoms, confirmed by genetic analysis, or with positive family history. All individual clinical records and family trees were carefully reviewed. Results Fifty eight HD cases in 39 families were identified, 25 of whom died before January 2014. Additionally, nine individuals were asymptomatic carriers and 245 were at 50% or 25% risk. Hospital database showed a higher PPV than Primary Care database and they were both equally sensitive. Combination of both sources detected 72% of cases with a PPV of 75%. Medical Genetics records identified 98% of HD patients. The estimated prevalence of HD was 5 per 100,000 (95% confidence interval [CI]: 4,5–5,4 per 100,000). Conclusions HD prevalence in Navarra is lower than recently estimated in other populations of European origin and it does not show a significantly increasing trend over the time. Past low prevalence figures are likely due to incomplete ascertainment, which did not include multiple sources and genetic data.