V Mattauch | PubMed Health

PubMed2001

[Record linkage with cryptographic identification data in a population-based cancer registry. Development, implementation and error rates].

BACKGROUND: Population-based cancer registries depend on the completeness of their case notification. At present, restrictive legal regulations in Germany requesting written informed consent of cancer patients hinder some health professionals, for example pathologists, from reporting to cancer registries. New cryptographic methods may be used to obtain record linkage based on anonymised data. OBJECTIVES: To assess the feasibility of a record linkage in the Münster Cancer Registry (EKR-MS) using cryptographic methods as compared to traditional methods based on personal identifiers. METHODS: We generated so called control numbers--a sequence of 23 alphanumeric signs--for 19 name related characteristics employing consecutively two different chiffrations. Record linkage was carried out using a semi-automatic computer program (AUTOMATCH) that generates probabilities of identity for pairs of case notifiation based on the information of control numbers only. Probabilities exceeding present limits lead to automatic decisions whereas the remaining linkage has to be decided manually. Plausibility-based rules helped to considerably reduce the amount of manual decisions. RESULTS: We compared traditional and cryptographic record linkage for all new reports received in the EKR-MS during 1998 (n = 27,262) against the background of n = 101,880 known cases in the registry data base. Setting traditional, text-based record linkage results to be the reference the cryptographic method resulted in a synonomous error (false creation of a new case) of almost 2% and a homonymous error (false link to a known case) of less than 0.5%. CONCLUSION: Cryptographic methods may be feasible procedures of record linkage in cancer registries. The size of the database of the EKR-MS prohibits extrapolation of findings to smaller registries. The error rates resulting in slight overestimation of disease rates that may seem acceptable. It should be noted though that cryptographic data are in many situations prohibitive for further epidemiologic research limiting the usefulness of the method exclusively to cancer registration under the given legal coercion.

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PubMed1999

[Lymphomas and leukemias in population-related cancer registries in Germany].

BACKGROUND: A German Federal law enacted in 1995 aims at nation-wide cancer registration, the details of realization based on local regulations being left to the individual Federal states. The impact of different approaches and regulations on the results of registration was investigated at three well-established records in the Saarland, Hamburg and North-Rhine Westphalia, taking the group of lymphoma and leukaemia (ICD 200-208) taken as an example. MATERIAL AND METHODS: Incidence and mortality rates calculated by the record files for the period from 1987 to 1994 were compared. The resulting mortality/incidence ratios were compared as well as the percentage of cases in each register with death certificates (DCO) as the only information source. RESULTS: There was a distinct increase of incidence rates visible in Hamburg and Münster. As far as the male patients was concerned, both records attained the level of Saarland at the end of the period. However, the leukaemia and lymphoma mortality figures for males and females was about 10% lower for Saarland than in the comparative regions. The male mortality incidence ratio was 0.55 for Saarland versus 0.60 average in Hamburg and Münster at the end of the period. In Saarland and Hamburg there was a decrease of DCO-cases from 14% to less than 6% in 1994. More constant values around 11% could be observed in the Münster registry. The distribution of diagnosis within the group as well as age-specific incidence rates for the selected diagnosis "lymphatic leukaemia" (ICD 204) and "Hodgkin's disease" (ICD 201) yielded only slight differences. CONCLUSION: The increase of incidence rates in Münster and Hamburg indicates more complete reporting. Assuming that the survival rates are the same in the three regions, the lower mortality in Saarland points to lower morbidity. Hence in spite of a definite approximation the cancer registries in Hamburg and Münster do not reach the level of completeness of the Saarland cancer registry. This may be due to the informed patient consent required by regional law for reports to the registry. To achieve completeness a special reporting procedure for pathological and haematological Institutes is mandatory. Simple indicators should be available in each registry for continuous estimation of completeness. Standardised case definitions and rules for the coding of diagnosis in cancer registries will improve national and international comparability and feasibility of data exchange.

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