Linkage of Australian national registry data using a statistical linkage key.

BACKGROUND: Data from clinical registries may be linked to gain additional insights into disease processes, risk factors and outcomes. Identifying information varies from full names, addresses and unique identification codes to statistical linkage keys to no direct identifying information at all. A number of databases in Australia contain the statistical linkage key 581 (SLK-581). Our aim was to investigate the ability to link data using SLK-581 between two national databases, and to compare this linkage to that achieved with direct identifiers or other non-identifying variables. METHODS: The Australian and New Zealand Society of Cardiothoracic Surgeons database (ANZSCTS-CSD) contains fully identified data. The Australian and New Zealand Intensive Care Society database (ANZICS-APD) contains non-identified data together with SLK-581. Identifying data is removed at participating hospitals prior to central collation and storage. We used the local hospital ANZICS-APD data at a large single tertiary centre prior to deidentification and linked this to ANZSCTS-CSD data. We compared linkage using SLK-581 to linkage using non-identifying variables (dates of admission and discharge, age and sex) and linkage using a complete set of unique identifiers. We compared the rate of match, rate of mismatch and clinical characteristics between unmatched patients using the different methods. RESULTS: There were 1283 patients eligible for matching in the ANZSCTS-CSD. 1242 were matched using unique identifiers. Using non-identifying variables 1151/1242 (92.6%) patients were matched. Using SLK-581, 1202/1242 (96.7%) patients were matched. The addition of non-identifying data to SLK-581 provided few additional patients (1211/1242, 97.5%). Patients who did not match were younger, had a higher mortality risk and more non-standard procedures vs matched patients. The differences between unmatched patients using different matching strategies were small. CONCLUSION: All strategies provided an acceptable linkage. SLK-581 improved the linkage compared to non-identifying variables, but was not as successful as direct identifiers. SLK-581 may be used to improve linkage between national registries where identifying information is not available or cannot be released.

Clinical characteristics and early mortality of patients undergoing coronary artery bypass grafting compared to percutaneous coronary intervention: insights from the Australasian Society of Cardiac and Thoracic Surgeons (ASCTS) and the Melbourne Interventional Group (MIG) Registries.

OBJECTIVES: Controversy continues over the optimal revascularisation strategy for patients with multi-vessel coronary artery disease. Clinical characteristics, risk profile, and mortality of patients undergoing coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) are thought to differ but there are limited contemporary comparative data. METHODS: We compared clinical characteristics, in-hospital and 30-day mortality of 3841 consecutive patients undergoing isolated CABG and 4417 undergoing PCI. Independent predictors of 30-day mortality were determined by multiple logistic regression analysis. RESULTS: CABG patients were older (p<0.01). The CABG group had a higher incidence of diabetes, heart failure, left ventricular ejection fraction <45%, multi-vessel coronary artery, peripheral vascular and cerebro-vascular disease (all p<0.01). Patients undergoing PCI had a higher incidence of recent myocardial infarction (MI) as the indication for revascularisation (p<0.01). In-hospital and 30-day mortality was 1.8% and 1.7% in the CABG group, and 1.4% and 1.8% in the PCI group, respectively. Independent predictors of 30-day mortality after CABG were age (odds ratio 1.1 per year, 95% confidence interval 1.0-1.1), cardiogenic shock (4.10, 1.7-10.5) and previous CABG (6.6, 2.4-17.7). Predictors after PCI were diabetes (2.7, 1.4-5.1), female gender (3.0, 1.6-5.5), renal failure (3.2, 1.2-8.0), MI<24h (4.0, 2.2-7.6), left main intervention (5.4, 1.0-27.7), heart failure (6.0, 2.6-14.0) and cardiogenic shock (11.7, 5.4-25.2). CONCLUSIONS: In contemporary clinical practice, CABG is preferred in patients with multi-vessel coronary and associated non-coronary vascular disease, while PCI is the dominant strategy for acute MI. Despite this, in-hospital and 30-day mortality rates were similar. Predictors of early mortality after CABG differ to those of PCI.

An Australian risk prediction model for 30-day mortality after isolated coronary artery bypass: the AusSCORE.

OBJECTIVE: Our objective was to identify risk factors associated with 30-day mortality after isolated coronary artery bypass grafting in the Australian context and to develop a preoperative model for 30-day mortality risk prediction. SUMMARY BACKGROUND DATA: Preoperative risk associated with cardiac surgery can be ascertained through a variety of risk prediction models, none of which is specific to the Australian population. Recently, it was shown that the widely used EuroSCORE model validated poorly for an Australian cohort. Hence, a valid model is required to appropriately guide surgeons and patients in assessing preoperative risk. METHODS: Data from the Australasian Society of Cardiac and Thoracic Surgeons database project was used. All patients undergoing isolated coronary artery bypass grafting between July 2001 and June 2005 were included for analysis. The data were divided into creation and validation sets. The data in the creation set was used to develop the model and then the model was validated in the validation set. Preoperative variables with a P value of less than .25 in chi(2) analysis were entered into multiple logistic regression analysis to develop a preoperative predictive model. Bootstrap and backward elimination methods were used to identify variables that are truly independent predictors of mortality, and 6 candidate models were identified. The Akaike Information Criteria (AIC) and prediction mean square error were used to select the final model (AusSCORE) from this group of candidate models. The AusSCORE model was then validated by average receiver operating characteristic, the P value for the Hosmer-Lemeshow goodness-of-fit test, and prediction mean square error obtained from n-fold validation. RESULTS: Over the 4-year period, 11,823 patients underwent cardiac surgery, of whom 65.9% (7709) had isolated coronary bypass procedures. The 30-day mortality rate for this group was 1.74% (134/7709). Factors selected as independent predictors in the preoperative isolated coronary bypass AusSCORE model were as follows: age, New York Heart Association class, ejection fraction estimate, urgency of procedure, previous cardiac surgery, hypercholesterolemia (lipid-lowering treatment), peripheral vascular disease, and cardiogenic shock. The average area under the receiver operating characteristic was 0.834, the P value for the Hosmer-Lemeshow chi(2) test statistic was 0.2415, and the prediction mean square error was 0.01869. CONCLUSION: We have developed a preoperative 30-day mortality risk prediction model for isolated coronary artery bypass grafting for the Australian cohort.

Initial twelve months experience and analysis for 2001-2002 from the Australasian Society of Cardiac and Thoracic Surgeons--Victorian database project.

UNLABELLED: The Australasian Society of Cardiac and Thoracic Surgeons (ASCTS) have established a database for the collection and analysis of the results of cardiac surgery in Australia and New Zealand. Initially data has been collected only in Victoria public hospitals. This report covers the first 12 months of data collection from 1st August 2001 to 1st July 2002. BACKGROUND: Whilst cardiac surgical performance in Australia is considered to be of a high standard equivalent to other developed countries, there is currently no systematic approach to data collection in order to provide performance indicators and benchmarks. The development of an Australasian cardiac surgical database and performance indicators will enable benchmarking and comparison with international standards which should lead to performance improvements. METHODS: A database definition set and standardised data collection form was developed by the ASCTS for all participating cardiac surgery units in public hospitals in Victoria. Opt-off consent for subject inclusion in the database was approved by each participating institutional ethics review committee. An electronic database and reporting application was developed. Data included in this analysis is from the initial 12 months collection from all hospitals participating in the project from 1st August 2001 to 31st July 2002. RESULTS: Overall, there were 2982 procedures performed in this period of which 2969 had sufficient data to be included in this analysis (99.5%). The majority of procedures 2017 (68%) being undertaken were isolated coronary artery bypass surgery (CABG). The mean age of all subjects undergoing procedures was 65 years (range: 18-91 years) and 70% were male. 64% of all procedures were elective and 6.1% emergency or salvage. Median post-procedure length of hospital stay for all procedures was 6.0 days and intensive care unit (ICU) stay was 23.0h. Re-operation for haemorrhage occurred in 2.1% of all cases and deep sternal infection in 0.4% of all cases. Crude 30-day operative mortality was 3.6% for all procedures; 2.1% for isolated CABG, 3.6% for valve procedures, 5.2% for valve and CABG and 11.4% for other cardiac surgical procedures. Mortality rates increased from 1.8% for elective procedures to 4.1% for urgent and 24.6% for emergency or salvage operations. In comparison to international figures from the USA and UK, mortality rates following isolated CABG were lower whilst average length of hospital stay post-procedure was higher. CONCLUSION: The ASCTS database project is now well established and the electronic database and reporting module is in operation in all participating sites. The risk-adjusted isolated operative mortality suggests cardiac surgical performance in Victoria compares well with international standards. As the database develops, local risk-adjustment models for mortality and morbidity for each procedure will be developed to enable appropriate between hospital comparisons.