Extent of misclassification of death from Creutzfeldt-Jakob disease in England 1979-96: retrospective examination of clinical records

Objective To investigate the extent to which deaths from Creutzfeldt-Jakob, disease were misclassified during 1979-96. Design Structured review of clinical records based on predetermined criteri a to determine whether death could have been due to sporadic or variant Cre utzfeldt-Jakob disease. Setting 100 health authorities and 275 NHS trusts in England. Subjects 1485 people who died aged 15-44 years from selected neurological d isorders in England during 1979-96. Main outcome measure Cause of death. Results The clinical records of 705 (48%) subjects were successfully traced . Tracing of clinical records was highest in subjects who died during 1990- 6. There was sufficient information in the records of 640 (91%) of the 705 subjects to exclude Creutzfeldt-Jakob disease as a cause of death. In 61 (9 %) subjects, there was insufficient information to reach any conclusion abo ut the validity of the cause of death recorded on the death certificate. Th e clinical records of four subjects were examined further by the National C reutzfeldt-Jakob Disease Surveillance Unit; none was thought to have died f rom Creutzfeldt-Jakob disease. Conclusions No new cases of sporadic or variant Creutzfeldt-Jakob disease w ere detected in a sample of deaths most likely to have included misclassifi ed cases. This suggests that the surveillance system is unlikely to have mi ssed a significant number of cases among people aged 15-44 years. Hence, an y rapid increase in the number of cases of variant Creutzfeldt-Jakob diseas e in this age group is likely to be real not artefactual.