A research registry: uses, development, and accuracy.

Many studies of population health, clinical epidemiology, and health services can be supported by a population-based research registry. Such a registry accurately defines the health insurance status for each individual over many years, magnifying the effectiveness of a cross-sectional registry (typically relevant for only a short duration) used in the administration of a health insurance plan. A research registry can distinguish between "well" individuals (no contact with the health care system), loss to follow-up (ineligibility associated with leaving the insurance plan), loss of continuity (two or more unlinked registrations over time for the same person), and mortality. The Manitoba research registry was developed to facilitate longitudinal studies; working within strict confidentiality controls, identifiers for each individual known to Manitoba Health since 1970 can be retrieved and a single unique identifier assigned. Careful reporting of changes in family registration numbers has enabled tracing area of residence, marital status, and family characteristics; results are equivalent to a daily census of the province. This article provides details on source materials, design, and quality of the registry, highlighting its value both for the development of integrated population health information systems and for research in general.

Clinical effectiveness of influenza vaccination in Manitoba.

OBJECTIVE: To assess the clinical effectiveness of influenza vaccination in preventing influenza-associated hospitalization and death. DESIGN: Case-control study. SETTING AND PATIENTS: Noninstitutionalized persons aged 45 years or older living in Manitoba, on December 1, 1982, and December 1, 1985. METHODS: Linked records of the Manitoba population registry, hospital-discharge abstracts, physician claims for ambulatory-patient visits and influenza vaccination, and vital statistics were used. A matched-set analysis estimated the clinical effectiveness of influenza vaccination in preventing hospital admissions and deaths from influenza-associated conditions during influenza A (H3N2) outbreak periods in 1982 to 1983 (12 weeks) and 1985 to 1986 (10 weeks). The analysis adjusted for hospital discharge and ambulatory care for high-risk conditions within the previous 15 months and 3 months, respectively. RESULTS: Influenza vaccination prevented 32% to 39% of hospital admissions with pneumonia and influenza and 15% to 34% of admissions with all respiratory conditions. Vaccination was 43% to 65% effective in preventing hospital deaths with these conditions (all listed diagnoses) and 27% to 30% effective in preventing deaths from all causes. CONCLUSION: Influenza vaccination has substantial clinical effectiveness in preventing hospital admission and death from influenza-associated conditions in noninstitutionalized individuals.

Registries and administrative data: organization and accuracy.

In this article the organization and accuracy of the population registry and administrative data base in Manitoba, Canada are discussed. The overall data management strategy and a framework for analyzing the accuracy of such data are presented. The generally high quality of the Manitoba registry file (necessary to track individuals over time) and the hospital claims is supported by comparisons with other data sources. Hospital claims' main quality problems concern the reliability of certain secondary diagnoses and the level of aggregation necessary for reasonable agreement with other data collection methods (such as chart reviews). Finally, some of the research possibilities associated with population registries and administrative data are outlined.

Disparity between influenza vaccination rates and risks for influenza-associated hospital discharge and death in Manitoba in 1982-1983.

OBJECTIVE: To determine, in a defined population, the percentage of persons who were discharged from a hospital or died of influenza-associated respiratory conditions who had a health care contact during the preceding vaccination season and to determine the relation between risk status for influenza-associated hospitalization and death and influenza vaccination rates. DESIGN: An observational study using linked-record analysis of medical claims data. SETTING AND PATIENTS: A probability sample of 100,000 noninstitutionalized adults living in Manitoba in 1982 to 1983. MEASUREMENTS: Analysis of medical claims for influenza vaccination and hospital discharges and deaths for influenza-associated respiratory conditions during the 1982-83 influenza vaccination season and influenza outbreak period. RESULTS: For the population as a whole, 50% to 60% of elderly persons (greater than or equal to 65 years of age) and 30% to 40% of younger persons had one or more health care contacts during the influenza vaccination season but fewer than 10% of all persons had been discharged from a hospital. In contrast, for elderly persons hospitalized with respiratory conditions during the influenza outbreak period, approximately 80% had at least one health care contact during the vaccination season. Among the elderly, 39% to 46% of all those discharged for influenza-associated respiratory conditions and 62% to 67% of those who died had been discharged from hospital during the previous vaccination season. Persons discharged with high-risk conditions during the vaccination season were at greater risk for hospitalization with influenza-associated respiratory conditions but were less likely to be vaccinated than were those at lower risk. CONCLUSIONS: Most persons who were hospitalized with influenza-associated respiratory conditions had contact with health care providers during the preceding influenza vaccination season. Among elderly patients, previous hospital care was common, especially among those who died. The disparity between influenza vaccination rates and risks for influenza-associated hospital discharge and death supports a strategy of hospital-based influenza vaccination.

Activated sludge systems with biomass particle support structures.

A mathematical model was developed to simulate the operation of an activated sludge system with biomass support particles. Based on the results of this simulation study, it would appear that a system with biomass particle supports offers several advantages not offered by conventional systems. These include the ability to resist failure from large hydraulic surges; stable nitrification under transient inhibitory conditions resulting from temperature changes, hydraulic surges, and/or toxic chemicals; and the ability to establish stable operating conditions with respect to both carbon oxidation and nitrification at short hydraulic retention times and low sludge ages.

Software for health care analysts: a modular approach.

The many concerns about the cost and quality of health care suggest the need to facilitate planners' using existing data bases for utilization review, program evaluation, and technology assessment. Despite both the availability of relevant data and widespread improvements in computing power, integrated computer software to permit analyses by nonspecialists has not previously been developed. This paper discusses the features of a health policy information system which aids working with hospital discharge abstracts, medical claims, cancer registries, and vital statistics files. Analyses of small area utilization, length of stay, in-hospital mortality, and readmissions are facilitated by this package. This information system, named the Health Applications System, includes an analysis module, three information management modules, and a set of record linkage modules. The modules were developed using the macroprocessor in the fourth-generation SAS system. Features of the software and their implications for data analysis are discussed.

Using administrative data for longitudinal research: comparisons with primary data collection.

This paper discusses the advantages and disadvantages of using administrative data for longitudinal research, focusing on loss to follow-up. Comparisons between research relying on primary data collection and that using data bases are made. After development of a suitable framework, follow-up in several well-known projects based on primary data collection (the Seven Countries project on coronary heart disease, the Massachusetts research on long-term care and the Pittsburgh clinical trial of tonsillectomy) is compared with follow-up using the Health Services Commission data base in Manitoba, Canada. Overall follow-up in the Manitoba research compares favorably with participation and follow-up rates in other studies based on primary data collection. Initial nonresponse and nonlocation are major problems with studies using primary data; failure to locate earlier respondents in subsequent waves results in a wide range of overall response rates. Data bases do not require researchers to contact individuals and hence follow-up is simplified. Eight year follow-up rates in the Manitoba data base are almost always over 80% and often over 90%. Because records can be flexibly summarized for each individual over time, data bases facilitate certain types of longitudinal studies which would be difficult, if not impossible, to perform using other methodologies. If the desired data are available and recorded with acceptable accuracy, administrative data banks hold considerable promise for the health care researcher.

The art and science of record linkage: methods that work with few identifiers.

Increasing use of administrative records for research purposes has led to the need to develop methods for linking records. Linkage of the data from the Manitoba Health Services Commission (MHSC) with Canadian Vital Statistics records was done to verify Manitoba deaths, to measure degree of agreement between the two data sets, and to link "cause of death" information from Vital Statistics back to medical histories. A multi-stage approach to matching was adopted. Individual records matching perfectly across a number of relevant variables in the two files were selected first, reducing the number of records going through the probability matching to manageable proportions. Overall, almost 96% of the MHSC records were well matched with Vital Statistics records. Both uses of the matched data and various ways to confirm data quality are discussed.

Building individual histories with registries. A case study.

This study concentrates on utilizing registries and assessing their quality for population-based research. A method of successive comparisons is used to develop and update a summary record of coverage (length of time on the registry) and mortality for each individual in the Manitoba Health Services Commission data base. Various ways to ascertain the accuracy of the summary records are discussed. These techniques are validated by efforts to follow over an 8-year period 4,794 individuals interviewed in 1971 as part of ongoing research on the Manitoba elderly. Ninety-seven percent of the total elderly sample (and 99% of those successfully matched with interviewees) were traced over 8 years. Deaths recorded on hospital claims but not on the master registry and possible unrecorded out-of-hospital deaths are outstanding problems with the Manitoba data base. Further checks against 1970-1977 vital statistics information in the Canadian Mortality Data Base will be made.

How good are the data? Reliability of one health care data bank.

This study investigates the reliability of the Manitoba Health Services Commission data bank from a variety of perspectives. Emphasizing diagnostic and surgical procedures, the research focuses on those areas in which problems exist and in which the data can be relied upon. Computerized comparisons are stressed, since they can provide cost-effective checks on data quality. One key to performing reliability studies inexpensively is finding information recorded independently: by separate individuals or organizations, at two different times, or in two or more data files. When a particular event has certain logical implications vis-à-vis another, inconsistencies can be located. Face sheet information and data on the performance of major surgical procedures were found to be reliably recorded in the Manitoba data bank. Collapsing ICD-8 diagnosis from medical claims into several categories proved much better than relying upon individual diagnoses. Problems in working with the data included difficulty in distinguishing between closely related surgical procedures and the underreporting of inhospital consultations and nonsurgical procedures.

Continuity of care: does it contribute to quality of care?

Continuity of care is defined and measured in terms of care received from a single physician, from several physicians practicing as a group and from physicians seen through referrals. All patients receiving tonsillectomy and adenoidectomy (T and As) in Manitoba for one year, as well as a group of similar individuals treated with respiratory illnesses but not having T and As, were studied. Several patient and physician characteristics were examined to determine their relationship to continuity of care. Continuity consistently increased with patient age, but appeared unrelated to several other variables. The links between continuity of care and quality of care were explored using process and outcome measures of quality. A cross-lagged panel analysis suggested no casual relationship between continuity and quality. These results contradict those of several other studies; they are important in that continuity of care is shown not to reduce one type of error of commission made by practitioners.