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PubMed1984

Rheumatic diseases in a health interview survey and in in-patient care. A record linkage study on two registers.

A record linkage was performed between the in-patient register of Stockholm County and the Stockholm County sample of a national health interview survey. The purpose was to describe and compare characteristics of the two registers, particularly as regards rheumatic diseases. All persons included in the health interview survey of 1977-78 were sought in the in-patient register for the same period. 37% of the population had reported long-term illness in the health interview survey and 22% had been hospitalized, according to the in-patient register. 11% reported a rheumatic disease in the health interview survey, but only 2% were hospitalized with a rheumatic diagnosis. Persons who reported a rheumatic disease in the health interview survey were compared with persons hospitalized with a rheumatic diagnosis by using items in the health interview survey on perceived health, physical mobility and work capacity. The most important difference between the groups was a much higher proportion of disabled persons in the hospitalized group. Perceived health was reported very similarly in the two groups. The reports on hospital episodes in the health interview survey were validated against the in-patient register. An under-reporting of 13% and several inaccuracies in the timing of the hospital episodes were found.

Adolescent↗

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.

Bias↗

PubMed1973

Epilepsy and pregnancy: a report from the Oxford Record Linkage Study.

The files of the Oxford Record Linkage Study were used to identify 223 infants delivered to 168 epileptic women as the result of 218 pregnancies. There were six stillbirths, two of which were grossly malformed. It was shown that the population of epileptic mothers differed significantly from the total reproducing population in respect of social class. Each pregnancy resulting in a livebirth was therefore matched exactly for social class, civil status, maternal age, parity, hospital, and year of delivery with three control deliveries resulting in livebirths. The defects noted at birth were abstracted from the Record Linkage files, and any subsequent hospital admissions or deaths of the children were also abstracted.There were highly significant excesses of congenital abnormalities among the infants born to epileptic mothers (13.8% of livebirths had some degree of defect of congenital origin compared with 5.6% of controls, P <0.0005). It was shown that neither the frequency with which the mother had fits nor the length of time she had had the epilepsy seemed to bear any relation to the frequency of defects in the offspring-with the exception of the two mothers who developed epilepsy in the first

Abnormalities, Drug-Induced↗

PubMed1998

Enhancing the power of record linkage involving low quality personal identifiers: use of the best link principle and cause of death prior likelihoods.

The Heartstart Scotland study collects details of all resuscitation attempts carried out by the Scottish Ambulance Service. The linkage between records for Heartstart study subjects who died before admission to a hospital and the national file of death records maintained by the Registrar General for Scotland is described. The conditions under which the Heartstart data is collected make it inevitable that the personal identifying information on which linkage must rely tends to be relatively incomplete and of low accuracy. The linkage process was able to use the best-link principle to take maximum advantage of the fact that, because the Heartstart subjects involved had died, there was an extremely high a priori probability that they would be represented on the national deaths file. In addition, although no cause of death information was recorded on the Heartstart records, a priori expectations of the distribution of causes of death among linked death records were used. Despite these enhancements, however, clerical resolution of a proportion of the potential links generated by the automatic algorithm significantly improved the accuracy of the linkage.

Ambulances↗

PubMed2003

Analysis of a probabilistic record linkage technique without human review.

We previously developed a deterministic record linkage algorithm demonstrating sensitivities approaching 90% while maintaining 100% specificity. Substantially better performance has been reported using probabilistic linkage techniques; however, such methods often incorporate human review into the process. To avoid human review, we employed an estimator function using the Expectation Maximization (EM) algorithm to establish a single true-link threshold. We compared the unsupervised probabilistic results against the manually reviewed gold-standard for two hospital registries, as well against our previous deterministic results. At an estimated specificity of 99.95%, actual specificities were 99.43% and 99.42% for registries A and B, respectively. At an estimated sensitivity of 99.95%, actual sensitivities were 99.19% and 98.99% for registries A and B, respectively. The EM algorithm estimated linkage parameters with acceptable accuracy, and was an improvement over the deterministic algorithm. Such a methodology may be used where record linkage is required, but human intervention is not possible or practical.

Algorithms↗

PubMed1996

Record linkage strategies, outpatient procedures, and administrative data.

By understanding the range of approaches implicit in modern record linkage, epidemiologists and health services researchers can better decide its suitability for their needs. The authors discuss a small record linkage project, providing a sense of where mistakes were made. The research first uses existing identification numbers as a gold standard for linking hospital abstracts and physician claims to investigate whether or not coronary angiography was performed on a given individual. Even if identification numbers are not available, a successful linkage (with more than 95% of the cases matched) may be possible under some circumstances. The linkage process highlights problems with the consistent recording of coronary angiography in inpatient and outpatient hospital abstracts. Our approach should prove useful when the same procedure is recorded in more than one place on a single file and when validating a procedure (or other event) across files is important. Given the growing number of health care databases and ongoing changes in the delivery of care, record linkage often can provide quality control and expand research opportunities in a timely fashion.

Abstracting and Indexing↗

PubMed2006

Assessing record linkage between health care and Vital Statistics databases using deterministic methods.

BACKGROUND: We assessed the linkage and correct linkage rate using deterministic record linkage among three commonly used Canadian databases, namely, the population registry, hospital discharge data and Vital Statistics registry. METHODS: Three combinations of four personal identifiers (surname, first name, sex and date of birth) were used to determine the optimal combination. The correct linkage rate was assessed using a unique personal health number available in all three databases. RESULTS: Among the three combinations, the combination of surname, sex, and date of birth had the highest linkage rate of 88.0% and 93.1%, and the second highest correct linkage rate of 96.9% and 98.9% between the population registry and Vital Statistics registry, and between the hospital discharge data and Vital Statistics registry in 2001, respectively. Adding the first name to the combination of the three identifiers above increased correct linkage by less than 1%, but at the cost of lowering the linkage rate almost by 10%. CONCLUSION: Our findings suggest that the combination of surname, sex and date of birth appears to be optimal using deterministic linkage. The linkage and correct linkage rates appear to vary by age and the type of database, but not by sex.

Adolescent↗

PubMed2004

Large-scale, population-based epidemiological studies with record linkage can be done in Germany.

Record linkage is an invaluable tool for many epidemiological studies. So far, however, in Europe it has mainly been used in Scandinavian countries with nationwide registration systems. Using the example of a large retrospective cohort study among migrants, we show that this method is also feasible in Germany, a country without central registries and unique identification numbers for citizens.

Epidemiologic Studies↗

PubMed2001

Record-linkage methodology for prescribing research.

Record-linkage refers to the linking together of data relating to the same individual from separate source files. In this paper, we discuss ways in which the technique can enhance observational prescribing research in large populations. We draw upon the work of the Medicines Monitoring Unit (MEMO), University of Dundee, to illustrate its contribution to prescribing research.

Data Collection↗

PubMed1990

Patients with multiple admissions in a psychiatric record linkage system.

Data from the Kingston Psychiatric Record Linkage System are used to examine the patterns of both inpatient and outpatient service utilization by patients with multiple admissions during a three year period compared with a control group with single admissions. The subgroup with drug and alcohol abuse disorders alone or in combination with a major functional disorder is examined in detail. An index of service utilization, which is based on aggregate inpatient stay and outpatient contacts, is calculated for each patient. Those with multiple admissions tend to be young, poorly educated, living alone and diagnosed with a major functional disorder; however, multiple regression analysis shows that other factors, as yet undetermined, contribute significantly to readmission. Among those with a major functional disorder, the subgroup of patients who also have drug and alcohol abuse disorders is particularly prone to multiple admissions. The need for specific services for patients with dual diagnoses is discussed. Early identification of those types of psychiatric patients who are likely to use services extensively is necessary to allow for planning and implementing of more cost-efficient and effective services.

Adjustment Disorders↗

PubMed1981

Record linkage for drug monitoring.

A study was carried out to assess the feasibility of using record linkage for drug monitoring. For two years, three types of records were collected for a total of 43 117 people: (1) details of basic attributes, such as sex and age; (2) details of prescriptions dispensed; and (3) records of hospital admissions, obstetric deliveries, and deaths. The records about each person were linked together, and analyses were performed to reveal associations between drugs and diagnoses. The study suggested that record linkage would be useful both for generating and for testing hypotheses about the adverse effects of drugs. The method would be especially valuable for detection of delayed effects (such as the induction of cancer), sudden deaths outside hospital, and effects of the fetus-all of which are difficult to study by other means. A full-scale project would need to cover a large population, and some of the practical issues that would arise are discussed.

Aged↗

PubMed2005

Work-related traffic crashes: a record linkage study.

AIM: To examine the characteristics of work-related traffic crashes involving drivers in New South Wales (NSW), Australia. METHODS: Probabilistic data record linkage were used to merge police crash records and workers compensation data for the period 1998-2002. RESULTS: The record linkage identified 13,124 drivers who were injured or died as a result of work-related traffic crash in New South Wales over the 5-year period. Approximately three quarters of driver casualties occurred during commuting (74.8%) with the rest occurring in the course of work. Male drivers made up around three quarters of these crashes and 93% of those that resulted in a fatality. Transport workers were the most frequent victims of work-related crashes while on duty (20.8%), with drivers of heavy trucks representing about half (48%) of all fatalities resulting from on duty work-related crashes. Nearly 1 in 6 male drivers were speeding at the time of the crash (15%, 95% CI 14.2-15.7) compared to less than 1 in 10 female drivers (9%, 95% CI 8.3-9.8) of female drivers. Male drivers were also significantly more likely to be fatigued at the time of the crash 7.6% (95% CI 7.0-8.2) compared to females 4.2% (95% CI 3.7-4.8). No significant difference was observed in the proportion of crashes involving fatigue between on duty and commuting traffic crashes. CONCLUSIONS: The study demonstrates the value of record linkage techniques in addressing some of the limitations of work-related data systems and in providing a more complete picture of the circumstances of occupational road crashes.

Accidents, Occupational↗

PubMed1998

Prenatal risk factors for cryptorchidism: a record linkage study.

Using data from the Oxford Record Linkage Study (ORLS), we conducted a case-control study to examine prenatal risk factors for cryptorchidism. We identified 1449 boys born during 1970-86 for whom there was a record of an orchidopexy during 1970-87. Up to eight controls were matched to each case on year of birth and hospital or place of delivery. For each boy and his mother we extracted abstracts of maternity and general hospital records from the ORLS. Low birthweight (trend P < 0.001), low social class (trend P < 0.001), breech presentation (relative risk 1.67; 95% confidence interval [CI] 1.16, 2.41), pre-eclampsia (1.17 [1.00, 1.37]), artificial feeding (1.22 [1.04, 1.45]) and episiotomy (1.13 [1.00, 1.27]) were identified as independent risk factors for cryptorchidism. Gestational age was not independently associated with cryptorchidism after adjusting for birthweight (P = 0.33), and this observation suggested that some cryptorchid boys may have suffered from intrauterine growth retardation. Low birthweight, breech presentation and pre-eclampsia may have in common poor placental function and impaired fetal growth, which may be causes of cryptorchidism.

Bottle Feeding↗

PubMed2006

How good is probabilistic record linkage to reconstruct reproductive histories? Results from the Aberdeen Children of the 1950s study.

BACKGROUND: Probabilistic record linkage is widely used in epidemiology, but studies of its validity are rare. Our aim was to validate its use to identify births to a cohort of women, being drawn from a large cohort of people born in Scotland in the early 1950s. METHODS: The Children of the 1950s cohort includes 5868 females born in Aberdeen 1950-56 who were in primary schools in the city in 1962. In 2001 a postal questionnaire was sent to the cohort members resident in the UK requesting information on offspring. Probabilistic record linkage (based on surname, maiden name, initials, date of birth and postcode) was used to link the females in the cohort to birth records held by the Scottish Maternity Record System (SMR 2). RESULTS: We attempted to mail a total of 5540 women; 3752 (68%) returned a completed questionnaire. Of these 86% reported having had at least one birth. Linkage to SMR 2 was attempted for 5634 women, one or more maternity records were found for 3743. There were 2604 women who reported at least one birth in the questionnaire and who were linked to one or more SMR 2 records. When judged against the questionnaire information, the linkage correctly identified 4930 births and missed 601 others. These mostly occurred outside of Scotland (147) or prior to full coverage by SMR 2 (454). There were 134 births incorrectly linked to SMR 2. CONCLUSION: Probabilistic record linkage to routine maternity records applied to population-based cohort, using name, date of birth and place of residence, can have high specificity, and as such may be reliably used in epidemiological research.

Adolescent↗

PubMed1997

[Record linkage of the elderly in the national surveys on the geriatric intermediate care facility].

Geriatric intermediate care facility, GICF, have been established since 1986 in Japan. The term of 'intermediate' denotes a facility midpoint between a hospital and home, with a powerful rehabilitation function. The annual governmental survey on GICF has been applied to all GICFs in Japan since 1989. This survey is a cross-sectional-type survey. For evaluating the role of GICF, we considered a type of cohort study using these surveys for four years by means of a record linkage method. This method is possible, because subjects of a survey for any year become subjects in the survey of the following year, if they have been in a GICF for more than one year. In this paper, for the purpose of preparing for a study of the role of GICF, we report some results about a record linkage for these surveys, and two continuing rates were calculated for these cohorts. Sources were personal records in 1989 to 1992 gathered by The National Survey on GICF in Japan. The record linkage method is as follows. We divided the annual personal records into several files by both the periods of the last admission and the survey year. Three cohorts, i.e. a cohort-89, a cohort-90 and a cohort-91 for persons for whom the first survey was 1989, 1990 and 1991, respectively are thus obtained. Next, we identified individuals from the annual files in each cohort. As personal names were not available, we identified individuals by sex, birth date, date of admission and facility number by the use of a personal computer and a FORTRAN program. Results were as follows. 1. Multiple matched persons were few (0.5% or less), and identification rates were 90% or more, despite the fact that basic linking variables were used. 2. Continuing rates were about 40% and decreased with new cohorts, while those of a fixed cohort were increased as length of stay increased. These reveal that recent admissions who stay continuously at a GICF were decreasing, but the longer the period for which the elderly stays at a GICF, the less possibility that he will be discharged. 3. Between record agreement rates for individuals over two years for unchangeable characteristics such as a place before admission which are expected to be 100% were about 80%. 4. A record linkage method appears to be useful for calculating continuing rates classified by any attribute.

Aged↗

PubMed2004

Practical introduction to record linkage for injury research.

The frequency of early fatality and the transient nature of emergency medical care mean that a single database will rarely suffice for population based injury research. Linking records from multiple data sources is therefore a promising method for injury surveillance or trauma system evaluation. The purpose of this article is to review the historical development of record linkage, provide a basic mathematical foundation, discuss some practical issues, and consider some ethical concerns. Clerical or computer assisted deterministic record linkage methods may suffice for some applications, but probabilistic methods are particularly useful for larger studies. The probabilistic method attempts to simulate human reasoning by comparing each of several elements from the two records. The basic mathematical specifications are derived algebraically from fundamental concepts of probability, although the theory can be extended to include more advanced mathematics. Probabilistic, deterministic, and clerical techniques may be combined in different ways depending upon the goal of the record linkage project. If a population parameter is being estimated for a purely statistical study, a completely probabilistic approach may be most efficient; for other applications, where the purpose is to make inferences about specific individuals based upon their data contained in two or more files, the need for a high positive predictive value would favor a deterministic method or a probabilistic method with careful clerical review. Whatever techniques are used, researchers must realize that the combination of data sources entails additional ethical obligations beyond the use of each source alone.

Databases, Factual↗

PubMed1994

Application of capture-recapture methods for disease monitoring: potential effects of imperfect record linkage.

Capture-recapture methods are increasingly employed to correct for underascertainment of cases in disease monitoring. Routine systems of disease monitoring, such as morbidity registries, are often prone to specific threats of validity, such as in imperfect diagnoses or imperfect record linkage. A quantitative assessment is given of the performance of the two-source capture-recapture method for disease monitoring in the presence of imperfect record linkage. The capture-recapture approach can eliminate underestimation of the number of eligible cases, which is typical for most disease monitoring systems, under certain conditions, including independence of sources of case ascertainment and perfect record linkage. Correction for underestimation remains less than perfect, however, in the case of false-positive matches, whereas application of capture-recapture methods leads to overestimation of case numbers in the presence of false-negative matches. A simple correction procedure to overcome potential overestimation by false-negative matches is outlined.

Data Collection↗

PubMed1987

Simplifying record linkage: software and strategy.

Although the methodology of record linkage is fairly well developed, there is a need for less expensive methods and simpler software to facilitate trying out different tactics to generate good linkages. The present work has built on a fourth generation language SAS (Statistical Analysis System) with accompanying macroprocessor, to develop a user-friendly and flexible system for both exact and probabilistic matching. The major features of the LINKS system are presented and illustrated using 1979-1984 information from the Manitoba Health Services Commission (MHSC) registry file with the Canadian Mortality Data Base. Initial runs with exact, then probabilistic, matching linked approximately 91% of the Vital Statistics records to corresponding MHSC records. Subsequent modification of parameters improved the linkage to 95%.

Database Management Systems↗