Best-Link Matching of Scottish Health Data Sets

Evaluation of a national complex oral health improvement programme: a population data linkage cohort study in Scotland

OBJECTIVES

Child dental caries is a global public health challenge with high prevalence and wide inequalities. A complex public health programme (Childsmile) was established. We aimed to evaluate the reach of the programme and its impact on child oral health.

SETTING

Education, health and community settings, Scotland-wide.

INTERVENTIONS

Childsmile (national oral health improvement programme) interventions: nursery-based fluoride varnish applications (FVAs) and supervised daily toothbrushing, community-based Dental Health Support Worker (DHSW) contacts and primary care dental practice visits-delivered to the population via a proportionate universal approach.

PARTICIPANTS

50 379 children (mean age=5.5 years, SD=0.3) attending local authority schools (2014/2015).

DESIGN

Population-based individual child-level data on four Childsmile interventions linked to dental inspection survey data to form a longitudinal cohort. Logistic regression assessed intervention reach and the independent impact of each intervention on caries experience, adjusting for age, sex and area-based Scottish Index of Multiple Deprivation (SIMD).

OUTCOME MEASURES

Reach of the programme is defined as the percentage of children receiving each intervention at least once by SIMD fifth. Obvious dental caries experience (presence/absence) is defined as the presence of decay (into dentine), missing (extracted) due to decay or filled deciduous teeth.

RESULTS

15 032 (29.8%) children had caries experience. The universal interventions had high population reach: nursery toothbrushing (89.1%), dental practice visits (70.5%). The targeted interventions strongly favoured children from the most deprived areas: DHSW contacts (SIMD 1: 29.5% vs SIMD 5: 7.7%), nursery FVAs (SIMD 1: 75.2% vs SIMD 5: 23.2%). Odds of caries experience were markedly lower among children participating in nursery toothbrushing (>3 years, adjusted OR (aOR)=0.60; 95% CI 0.55 to 0.66) and attending dental practice (≥6 visits, aOR=0.55; 95% CI 0.50 to 0.61). The findings were less clear for DHSW contacts. Nursery FVAs were not independently associated with caries experience.

CONCLUSIONS

The universal interventions, nursery toothbrushing and regular dental practice visits were independently and most strongly associated with reduced odds of caries experience in the cohort, with nursery toothbrushing having the greatest impact among children in areas of high deprivation.

Trends in incidence and case fatality of acute myocardial infarction, angina and coronary revascularisation in people with and without type 2 diabetes in Scotland between 2006 and 2015

AIMS/HYPOTHESIS

The aim of the study was to examine trends in the incidence and case fatality of acute myocardial infarction (AMI) and in hospital admissions for angina and coronary revascularisation procedures in people with type 2 diabetes and in people without diabetes in Scotland between 2006 and 2015.

METHODS

In this retrospective cohort study, AMI, angina and revascularisation event data were obtained for adults from hospital admissions and death records linked to a population-based diabetes register. Incidence by diabetes status was estimated using negative binomial models with adjustment or stratification by age, sex, deprivation and calendar year. Logistic regression was used to estimate AMI case fatality by diabetes status.

RESULTS

There were 129,926 incident AMI events, 41,263 angina admissions and 69,875 coronary revascularisation procedures carried out during 34.9 million person-years of follow-up. The adjusted incidence of AMI, angina and revascularisation procedures declined by 2.0% (95% CI 1.73%, 2.26%), 9.62% (95% CI 9.22%, 10.01%) and 0.35% (95% CI -0.09%, 0.79%) per year, respectively. The rate of decline did not differ materially by diabetes status. RRs of AMI for type 2 diabetes were 1.86 (95% CI 1.74, 1.98) for men and 2.32 (95% CI 2.15, 2.51) for women. Of the 77,211 people admitted to hospital with a first AMI, 7842 (10.2%) died within 30 days of admission. Case fatality was higher in people with type 2 diabetes than in people without diabetes and declined in both groups by 7.93% (95% CI 7.03%, 8.82%) per year.

CONCLUSIONS/INTERPRETATION

The incidence of AMI, angina, revascularisation and AMI case fatality has declined over time, but the increased risk associated with type 2 diabetes has remained approximately constant.

Technical challenges of providing record linkage services for research

Background

Record linkage techniques are widely used to enable health researchers to gain event based longitudinal information for entire populations. The task of record linkage is increasingly being undertaken by specialised linkage units (SLUs). In addition to the complexity of undertaking probabilistic record linkage, these units face additional technical challenges in providing record linkage ‘as a service’ for research. The extent of this functionality, and approaches to solving these issues, has had little focus in the record linkage literature. Few, if any, of the record linkage packages or systems currently used by SLUs include the full range of functions required.

Methods

This paper identifies and discusses some of the functions that are required or undertaken by SLUs in the provision of record linkage services. These include managing routine, on-going linkage; storing and handling changing data; handling different linkage scenarios; accommodating ever increasing datasets. Automated linkage processes are one way of ensuring consistency of results and scalability of service.

Results

Alternative solutions to some of these challenges are presented. By maintaining a full history of links, and storing pairwise information, many of the challenges around handling ‘open’ records, and providing automated managed extractions are solved. A number of these solutions were implemented as part of the development of the National Linkage System (NLS) by the Centre for Data Linkage (part of the Population Health Research Network) in Australia.

Conclusions

The demand for, and complexity of, linkage services is growing. This presents as a challenge to SLUs as they seek to service the varying needs of dozens of research projects annually. Linkage units need to be both flexible and scalable to meet this demand. It is hoped the solutions presented here can help mitigate these difficulties.

Informing the 'early years' agenda in Scotland: understanding infant feeding patterns using linked datasets

BACKGROUND

Providing infants with the 'best possible start in life' is a priority for the Scottish Government. This is reflected in policy and health promotion strategies to increase breast feeding, which gives the best source of nutrients for healthy infant growth and development. However, the rate of breast feeding in Scotland remains one of the lowest in Europe. Information is needed to provide a better understanding of infant feeding and its impact on child health. This paper describes the development of a unique population-wide resource created to explore infant feeding and child health in Scotland.

METHODS

Descriptive and multivariate analyses of linked routine/administrative maternal and infant health records for 731,595 infants born in Scotland between 1997 and 2009.

RESULTS

A linked dataset was created containing a wide range of background, parental, maternal, birth and health service characteristics for a representative sample of infants born in Scotland over the study period. There was high coverage and completeness of infant feeding and other demographic, maternal and infant records. The results confirmed the importance of an enabling environment--cultural, family, health service and other maternal and infant health-related factors--in increasing the likelihood to breast feed.

CONCLUSIONS

Using the linked dataset, it was possible to investigate the determinants of breast feeding for a representative sample of Scottish infants born between 1997 and 2009. The linked dataset is an important resource that has potential uses in research, policy design and targeting intervention programmes.

Record linkage in Scotland and its applications to health research

AIMS AND OBJECTIVES

  This paper will focus on the key concepts behind record linkage and describe how probability matching of Scottish health records can be used for national health research.

BACKGROUND

  Record linkage can bring together two or more records relating to the same individual. This allows information from multiple sources to be joined together to produce richer data sets for research purposes and has wide applicability in public health and epidemiological research. The probability matching techniques underpinning record linkage bring together records on a patient basis using key identifying information on each record. Scotland has a strong track record for performing linkage for research purposes owing to routinely collected and well-maintained national administrative health data sets, the emergence of the Scottish record linkage system and organisations like the Information Services Division of NHS National Services Scotland who centrally hold permanently linked patient-based databases. Design.  A record linkage retrospective population cohort study is described within this paper.

METHODS

  The paper will describe current linkage methodology before discussing typical applications in the setting of Information Services Division and focusing on a particular linkage study investigating rates and risk factors for gastroschisis.

RESULTS

  Conclusions from the gastroschisis study are typical of the types of important findings drawn from analysing linked health data.

CONCLUSIONS

  Scotland's good track record for linking records for health research is evidenced by the high volume of research projects, publications and findings resulting from probability matching of national health data. Relevance to clinical practice.  Record linkage allows information relating to the same person held across different data sources to be brought together. Probabilistic record linkage can overcome data quality issues, producing accurate matches. This allows linked, analysable, patient-based databases, capable of answering complex research questions, to be produced from several data sources with wide applications in the field of health research.

Administrative data linkage as a tool for child maltreatment research

Linking administrative data records for the same individuals across services and over time offers a powerful, population-wide resource for child maltreatment research that can be used to identify risk and protective factors and to examine outcomes. Multistage de-identification processes have been developed to protect privacy and maintain confidentiality of the datasets. Lack of information on those not coming to the attention of child protection agencies, and limited information on certain variables, such as individual-level SES and parenting practices, is outweighed by strengths that include large and unbiased samples, objective measures, comprehensive long-term follow-up, continuous data collection, and relatively low expense. Ever emerging methodologies and expanded holdings ensure that research using linked population-wide databases will make important contributions to the study of child maltreatment.

History of the Rochester Epidemiology Project: half a century of medical records linkage in a US population

The Rochester Epidemiology Project (REP) has maintained a comprehensive medical records linkage system for nearly half a century for almost all persons residing in Olmsted County, Minnesota. Herein, we provide a brief history of the REP before and after 1966, the year in which the REP was officially established. The key protagonists before 1966 were Henry Plummer, Mabel Root, and Joseph Berkson, who developed a medical records linkage system at Mayo Clinic. In 1966, Leonard Kurland established collaborative agreements with other local health care providers (hospitals, physician groups, and clinics [primarily Olmsted Medical Center]) to develop a medical records linkage system that covered the entire population of Olmsted County, and he obtained funding from the National Institutes of Health to support the new system. In 1997, L. Joseph Melton III addressed emerging concerns about the confidentiality of medical record information by introducing a broad patient research authorization as per Minnesota state law. We describe how the key protagonists of the REP have responded to challenges posed by evolving medical knowledge, information technology, and public expectation and policy. In addition, we provide a general description of the system; discuss issues of data quality, reliability, and validity; describe the research team structure; provide information about funding; and compare the REP with other medical information systems. The REP can serve as a model for the development of similar research infrastructures in the United States and worldwide.

A record linkage process of a cervical cancer screening database

This paper aims at to present the integration of the files of the Brazilian Cervical Cancer Information System (SISCOLO) in order to identify all women in the system. SISCOLO has the exam as the unit of observation and the women are not uniquely identified. It has two main tables: histology and cytology, containing the histological and cytological examinations of women, respectively. In this study, data from June 2006 to December 2009 were used. Each table was linked with itself and with the other through record linkage methods. The integration identified 6236 women in the histology table and 1,678,993 in the cytology table. 5324 women from the histology table had records in the cytology table. The sensitivities were above 90% and the specificities and precisions near 100%. This study showed that it is possible to integrate SISCOLO to produce indicators for the evaluation of the cervical cancer screening programme taking the woman as the unit of observation.

Administrative record linkage as a tool for public health research

Linked administrative databases offer a powerful resource for studying important public health issues. Methods developed and implemented in several jurisdictions across the globe have achieved high-quality linkages for conducting health and social research without compromising confidentiality. Key data available for linkage include health services utilization, population registries, place of residence, family ties, educational outcomes, and use of social services. Linking events for large populations of individuals across disparate sources and over time permits a range of research possibilities, including the capacity to study low-prevalence exposure-disease associations, multiple outcome domains within the same cohort of individuals, service utilization and chronic disease patterns, and life course and transgenerational transmission of health. Limited information on variables such as individual-level socioeconomic status (SES) and social supports is outweighed by strengths that include comprehensive follow-up, continuous data collection, objective measures, and relatively low expense. Ever advancing methodologies and data holdings guarantee that research using linked administrative databases will make increasingly important contributions to public health research.

Use of a medical records linkage system to enumerate a dynamic population over time: the Rochester epidemiology project

The Rochester Epidemiology Project (REP) is a unique research infrastructure in which the medical records of virtually all persons residing in Olmsted County, Minnesota, for over 40 years have been linked and archived. In the present article, the authors describe how the REP links medical records from multiple health care institutions to specific individuals and how residency is confirmed over time. Additionally, the authors provide evidence for the validity of the REP Census enumeration. Between 1966 and 2008, 1,145,856 medical records were linked to 486,564 individuals in the REP. The REP Census was found to be valid when compared with a list of residents obtained from random digit dialing, a list of residents of nursing homes and senior citizen complexes, a commercial list of residents, and a manual review of records. In addition, the REP Census counts were comparable to those of 4 decennial US censuses (e.g., it included 104.1% of 1970 and 102.7% of 2000 census counts). The duration for which each person was captured in the system varied greatly by age and calendar year; however, the duration was typically substantial. Comprehensive medical records linkage systems like the REP can be used to maintain a continuously updated census and to provide an optimal sampling framework for epidemiologic studies.

Underestimated and under-recognized: the late consequences of acute coronary syndrome (GRACE UK-Belgian Study)

AIM

To define the long-term outcome of patients presenting with acute coronary syndrome [ST-segment elevation myocardial infarction (STEMI), and non-STEMI and unstable angina acute coronary syndrome (ACS) without biomarker elevation] and to test the hypothesis that the GRACE (Global Registry of Acute Coronary Events) risk score predicts mortality and death/MI at 5 years.

METHODS AND RESULTS

In the GRACE long-term study, UK and Belgian centres prospectively recruited and followed ACS patients for a median of 5 years (1797 days). Primary outcome events: deaths, cardiovascular deaths (CVDs) and MIs. Secondary events: stroke and re-hospitalization for ACS. There were 736 deaths, 19.8% (482 CVDs, 13%) and 347 (9.3%) MIs (>24 h), 261 strokes (7.7%), and 452 (17%) subsequent revascularizations. Rehospitalization was common: average 1.6 per patient; 31.2% had >1 admission, 9.2% had 5+ admissions. These events were despite high rates of guideline indicated therapies. The GRACE score was highly predictive of all-cause death, CVD, and CVD/MI at 5 years (death: χ(2) likelihood ratio 632; Wald 709.9, P< 0.0001, C-statistic 0.77; for CVD C-statistic 0.75, P < 0.0001; CVD/MI C-statistic 0.70, P < 0.0001). Compared with the low-risk GRACE stratum (ESC Guideline criteria), those with intermediate [hazard ratio (HR) 2.14, 95% CI 1.63, 2.81] and those with high-risk (HR 6.36, 95% CI 4.95, 8.16) had two- and six-fold higher risk of later death (Cox proportional hazard). A landmark analysis after 6 months confirmed that the GRACE score predicted long-term death (χ(2) likelihood ratio 265.4; Wald 289.5, P < 0.0001). Although in-hospital rates of death and MI are higher following STEMI, the cumulative rates of death (and CVD) were not different, by class of ACS, over the duration of follow-up (Wilcoxon = 1.5597, df = 1, P = 0.21). At 5 years after STEMI 269/1403 (19%) died; after non-STEMI 262/1170 (22%) after unstable angina (UA) 149/850 (17%). Two-thirds (68%) of STEMI deaths occurred after initial hospital discharge, but this was 86% for non-STEMI and 97% for UA.

CONCLUSION

The GRACE risk score predicts early and 5 year death and CVD/MI. Five year morbidity and mortality are as high in patients following non-ST MI and UA as seen following STEMI. Their morbidity burden is high (MI, stroke, readmissions) and the substantial late mortality in non-STE ACS is under-recognized. The findings highlight the importance of pursuing novel approaches to diminish long-term risk.

Impact of record-linkage methodology on performance indicators and multivariate relationships

Program evaluation often requires the linkage of records from independently maintained data systems (e.g., substance abuse treatment and criminal justice). Data entry errors (e.g., misspelled names, transposed digits) complicate the linkage task. In this investigation, three record-linkage algorithms (match-merge, common patient identifier, and probabilistic) are used to link recipients of publicly funded outpatient substance abuse treatment to statewide arrest and death data. The impact of record-linkage algorithm on performance indicators, prevalence indicators (i.e., arrest rates, and death rates), and hazard ratios derived from a multivariate survival analysis predicting risk of arrest following admission to outpatient substance abuse treatment is evaluated. Choice of algorithm substantially impacted estimates of arrest rates (range: year prior to admission, 39.8%-53.4%; year following admission, 24.7%-33.1%). The hazard ratio associated with "prior arrest" as a predictor of arrest following admission to outpatient substance abuse treatment (hazard ratio range = 0.20-0.37, p < .05) was also influenced by algorithm choice.

Probabilistic record linkage and an automated procedure to minimize the undecided-matched pair problem

Probabilistic record linkage allows the assembling of information from different data sources. We present a procedure when a one-to-one relationship between records in different files is expected but not found. Data were births and infant deaths, 1998-birth cohort, city of São Paulo, Brazil. Pairs for which a one-to-one relationship was obtained and a best-link was found with the highest weight were taken as unequivocally matched pairs and provided information to decide on the remaining pairs. For these, an expected relationship between differences in dates of death and birth registration was found; and places of birth and death registration for neonatal deaths were likely to be the same. Such evidence was used to solve for the remaining pairs. We reduced the number of non-uniquely matched records and of uncertain matches, and increased the number of uniquely matched pairs from 2,249 to 2,827. Future research using record linkage should use strategies from first record linkage runs before a full clerical review (the standard procedure under uncertainty) to efficiently retrieve matches.

Policy analysis in an information-rich environment

Population-based insurance systems using longitudinal administrative data and record linkage techniques have helped create "information-rich" environments in several sites around the world. The output of five research groups using administrative data (Oxford, Western Australia, and three Canadian centres: Manitoba, Ontario and British Columbia) was analysed from contacts with the research groups and through use of the National Library of Medicine's PubMed and Medical Subject Headings (MeSH) categories. MeSH words "utilization", "economics", "physicians", and "physician practice patterns" more frequently characterized the research by the three Canadian centres than that of the other sites. With core funding for deliverables negotiated with the provincial health ministries, Canadian researchers have been more likely to use linked databases for policy analyses. Manitoba examples highlight the capabilities associated with these information-rich environments. They include the ability to analyse interventions longitudinally; to compare regions, areas and hospitals in defined populations; to combine information on patients and physicians; to add up expenditures for different services within the Canadian health-care system; and to examine population health issues in areas such as education and family services. Well-organized data and the capability for rapid response have been critical for timely policy analysis in Manitoba. A number of successes are mentioned; less successful efforts to influence practice patterns and to modify the internal workings of hospitals are noted. Investments in filling gaps in data collection and in enriching existing data would facilitate additional research. Planning and managing health care for an entire population has benefited greatly from the development of an information-rich environment.

Working more productively: tools for administrative data

OBJECTIVE

This paper describes a web-based resource (http://www.umanitoba.ca/centres/mchp/concept/) that contains a series of tools for working with administrative data. This work in knowledge management represents an effort to document, find, and transfer concepts and techniques, both within the local research group and to a more broadly defined user community. Concepts and associated computer programs are made as "modular" as possible to facilitate easy transfer from one project to another.

STUDY SETTING/DATA SOURCES

Tools to work with a registry, longitudinal administrative data, and special files (survey and clinical) from the Province of Manitoba, Canada in the 1990-2003 period.

DATA COLLECTION

Literature review and analyses of web site utilization were used to generate the findings.

PRINCIPAL FINDINGS

The Internet-based Concept Dictionary and SAS macros developed in Manitoba are being used in a growing number of research centers. Nearly 32,000 hits from more than 10,200 hosts in a recent month demonstrate broad interest in the Concept Dictionary.

CONCLUSIONS

The tools, taken together, make up a knowledge repository and research production system that aid local work and have great potential internationally. Modular software provides considerable efficiency. The merging of documentation and researcher-to-researcher dissemination keeps costs manageable.

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.