br For a planned population based cohort study of
For a planned population-based cohort study of patients with three common cancers requiring further information on therapy and care from eligible patients, only 47% of patients give consent; so while in-ternal comparisons within the group may be valid, the whole group is not, as planned, a representative population-based study . A small study requiring consent from the review of medical records of men with prostate cancer achieved in 84% response rate, but at a considerable cost .
Some population groups are particularly difficult to reach. To study unmet needs, in Australia an attempt was made to contact a re-presentative sample of adolescent and young adult survivors of cancer. Initial identification could easily be made from standard existing re-gistries, but an active clinical consent protocol was used by the re-gistries approaching subjects through their clinicians. As a result the overall consent rate was only 7.8%, due mainly to non-responses from clinicians or contact not being established. In Veratridine very few in-dividuals who were approached refused personal consent .
Data completeness has also been threatened on a larger scale. In regions of Germany, law changes in the 1980s requiring informed consent for cancer registries which previously had included all cases of cancer without consent for over 50 years. This quickly resulted in at least 30% failure of registration, and eventual failure of the registries as they were no longer valuable by being incomplete. Subsequent attempts to improve this led to a complicated system using two centres produced duplicate registrations and continued failure . Changes in regula-tions by large jurisdictions such as the European Union can threaten the completeness or existence of registration and essential linkages .
Variations in administrative decisions and ethical committee deci-sions can threaten registration issues . Even in the same legislative climate, with a common protocol, different organisations can vary greatly on how patients are approached for consent and registration . The efficiency and transparency in the operation of administrative structures and ethical committees also needs considered, particularly if several jurisdictions are involved . It has been noted that “those responsible for framing guidelines on the handling of clinical data and for advising doctors should consider issues related to health surveil-lance so as public health is not put at risk” .
A restrictive policy is not supported by the general public. In a survey of 2872 respondents in the UK in 2005, 95% considered the existence of a national cancer registry with enough detail to assess ef-fectiveness of treatment as useful, and 81% supported legal registration of all cases of cancer to such a registry . Only 16% had any ob-jection to being identified and approached for further study from such a registry.
There is a strong argument that the operation of clinical registries, which require only the information already recorded on hospital and pathology records, and do not involve any direct contact with the
Proportions of subjects with missing data.
patient, should be operated without any requirement for specific con-sent.
Despite those arguments, legislative and management policies re-lating to data collection, and the interpretations by individual organi-sations and by ethics committees, still often require informed consent, even for clinical registries using routine data. This may relate to failure to distinguish between observational work using routine data, which when done by healthcare management as part of routine administration proceeds with little comment, and intrusive research epitomised at the extreme by clinical trials . Traditional medical ethics has its background in the experimental therapies of individual patients, which have guided major ethical initiatives . Clinical trials are valid be-cause the essential comparisons are internal, despite the fact that the subjects involved in a trial may not be representative of the source populations. With registries however, the loss of representativeness caused by a requirement for consent is critical, as a major function of the registries is to provide information on the management and out-come of all patients in a defined population.
It can be argued however that registration itself can be threatening and may be viewed as undesirable , in which case a specific consent policy may be appropriate. An opt-out system may be appropriate, as monomer allows those who feel sensitive to such issues to decline, but in practice very few do, so the remaining database may be representative. Using an opt-out consent system, in Australia an Internet-based database for colorectal neoplasia has been operating with almost 100% completion ; and an opt-out system is used to achieve high recruitment for a detailed lung cancer registry . An opt-out system is used for a breast implant registry in the Netherlands, after previous attempts had pro-duced only unreliable and incomplete information .