Volume 8: Variant CJD
4. Work of the CJD Surveillance Unit
Prospective study of CJD

4.6 The other major task was to establish a system for the prospective surveillance of CJD that would be able to detect any changes in epidemiology or clinical characteristics, as a result of the emergence of BSE. ¹ The main epidemiological parameters investigated included number of cases, geographical distribution of cases and occupational incidence.

4.7 Primarily, this was achieved by direct referral of any suspect cases of CJD through the neurological network, comprising neurologists, neurophysiologists and neuropathologists. These professionals were also asked to report all cases of subacute dementing illnesses or progressive cerebellar dysfunction in specific occupational groups (veterinarians, herdsmen, slaughtermen, farmers, butchers and laboratory workers). ² However, as a precaution, all death certificates mentioning CJD were also obtained from the OPCS, and equivalent bodies in Scotland and Northern Ireland, and assessed. ³

4.8 Another proposal for improving ascertainment was that CJD should be made a notifiable disease. This was put forward during evidence to the Agriculture Select Committee's inquiry into BSE which reported in July 1990, but it was not supported by either the CMO or Dr Will. ⁴ In order to make CJD a notifiable disease, specific diagnostic criteria, which cases would have to fulfil, would have to be established. Dr Will believed that some cases might then be missed as there might be a reluctance to notify cases that did not fulfil the criteria absolutely. In addition, the necessary diagnostic criteria could only be used in the later stages of disease and that might result in cases being missed. ⁵

4.9 Dr Will's opinion was supported by the EU Surveillance Group in 1994 and recent data from this Group has revealed that making CJD a notifiable disease was not likely to improve case ascertainment but might actually be detrimental. For example, the introduction of notification in Slovakia has been stated to have resulted in a decrease in the number of referrals. ⁶

4.10 Each patient referred to the CJDSU was visited in order to verify the diagnosis and obtain the relevant information. ⁷ The clinical and epidemiological information was obtained by a standard questionnaire. Because of the rapid progress of the illness, this could not be answered by the patient but instead was answered by the relatives of the patient.

4.11 After obtaining this information, the CJDSU compared the retrospective and prospective data in an attempt to reveal any change in either the epidemiology or the clinical characteristics of CJD. ⁸