Mortality from Human Transmissible Spongiform Encephalopathies: A Record Linkage Study

Abstract

To evaluate the ability of the Italian Creutzfeldt-Jakob (CJD) register to detect human transmissible spongiform encephalopathy (TSE) cases we compared mortality data from the CJD register with those obtained from death certificates collected by the Italian National Census Bureau (ISTAT) between 1993 and 1999. We used the method of record linkage to compare and integrate data from these two sources. The integrated estimate of TSE deaths was 457: 183 deaths recorded by the CJD register and ISTAT, 210 cases only by the CJD register, and 64 cases only by ISTAT. The average integrated estimated mortality rate was 1.58 deaths per million people per year over the study period and peaked in 1999 at 2.13. This figure is similar to that obtained from data from the CJD register alone in the years 2000–2002. The increase in mortality rates is likely due to an improvement in case ascertainment. The misclassification of cases by ISTAT was above 50% from 1996 onward, suggesting that using only death certificates is not a reliable way to monitor TSE cases in Italy.