Graeme L. Hickey

How does EuroSCORE II perform in UK cardiac surgery; an analysis of 23 740 patients from the Society for Cardiothoracic Surgery in Great Britain and Ireland National Database

Objective The original EuroSCORE models are poorly calibrated for predicting mortality in contemporary cardiac surgery. EuroSCORE II has been proposed as a new risk model. The objective of this study was to assess the performance of EuroSCORE II in UK cardiac surgery. Design A cross-sectional analysis of prospectively collected multi-centre clinical audit data, from the Society for Cardiothoracic Surgery in Great Britain and Ireland Database. Setting All NHS hospitals, and some UK private hospitals performing adult cardiac surgery. Patients 23 740 procedures at 41 hospitals between July 2010 and March 2011. Main outcome measures The main outcome measure was in-hospital mortality. Model calibration (Hosmer–Lemeshow test, calibration plot) and discrimination (area under receiver operating characteristic curve) were assessed in the overall cohort and clinically defined sub-groups. Results The mean age at procedure was 67.1 years (SD 11.8) and 27.7% were women. The overall mortality was 3.1% with a EuroSCORE II predicted mortality of 3.4%. Calibration was good overall but the model failed the Hosmer–Lemeshow test (p=0.003) mainly due to over-prediction in the highest and lowest-risk patients. Calibration was poor for isolated coronary artery bypass graft surgery (Hosmer–Lemeshow, p<0.001). The model had good discrimination overall (area under receiver operating characteristic curve 0.808, 95% CI 0.793 to 0.824) and in all clinical sub-groups analysed. Conclusions EuroSCORE II performs well overall in the UK and is an acceptable contemporary generic cardiac surgery risk model. However, the model is poorly calibrated for isolated coronary artery bypass graft surgery and in both the highest and lowest risk patients. Regular revalidation of EuroSCORE II will be needed to identify calibration drift or clinical inconsistencies, which commonly emerge in clinical prediction models.

Global scale variation in the salinity sensitivity of riverine macroinvertebrates: Eastern Australia, France, Israel and South Africa

Salinity is a key abiotic property of inland waters; it has a major influence on biotic communities and is affected by many natural and anthropogenic processes. Salinity of inland waters tends to increase with aridity, and biota of inland waters may have evolved greater salt tolerance in more arid regions. Here we compare the sensitivity of stream macroinvertebrate species to salinity from a relatively wet region in France (Lorraine and Brittany) to that in three relatively arid regions eastern Australia (Victoria, Queensland and Tasmania), South Africa (south-east of the Eastern Cape Province) and Israel using the identical experimental method in all locations. The species whose salinity tolerance was tested, were somewhat more salt tolerant in eastern Australia and South Africa than France, with those in Israel being intermediate. However, by far the greatest source of variation in species sensitivity was between taxonomic groups (Order and Class) and not between the regions. We used a Bayesian statistical model to estimate the species sensitivity distributions (SSDs) for salinity in eastern Australia and France adjusting for the assemblages of species in these regions. The assemblage in France was slightly more salinity sensitive than that in eastern Australia. We therefore suggest that regional salinity sensitivity is therefore likely to depend most on the taxonomic composition of respective macroinvertebrate assemblages. On this basis it would be possible to screen rivers globally for risk from salinisation.

Preoperative cardiopulmonary exercise testing and risk of early mortality following abdominal aortic aneurysm repair.

Cardiopulmonary exercise testing (CPET) provides an objective assessment of functional capacity. The aim of this study was to assess whether preoperative CPET identifies patients at risk of early death following elective open and endovascular abdominal aortic aneurysm (AAA) repair.

Clinical registries: governance, management, analysis and applications.

Clinical registries will have an increasingly important role to play in health-care, with a number already established in cardiac surgery. This review covers the fundamentals of establishing and managing clinical registries, including legal and ethical frameworks along with intellectual property attribution. Also discussed are important issues relating to the processing of data, data extraction and conducting analyses using registry data.

Publishing cardiac surgery mortality rates: lessons for other specialties

The Society for Cardiothoracic Surgeons in Great Britain and Ireland has been reporting outcome data for named surgeons since 2005. Ben Bridgewater and colleagues discuss their experiences and the implications for other specialties

Making species salinity sensitivity distributions reflective of naturally occurring communities: Using rapid testing and Bayesian statistics

Species sensitivity distributions (SSDs) may accurately predict the proportion of species in a community that are at hazard from environmental contaminants only if they contain sensitivity data from a large sample of species representative of the mix of species present in the locality or habitat of interest. With current widely accepted ecotoxicological methods, however, this rarely occurs. Two recent suggestions address this problem. First, use rapid toxicity tests, which are less rigorous than conventional tests, to approximate experimentally the sensitivity of many species quickly and in approximate proportion to naturally occurring communities. Second, use expert judgements regarding the sensitivity of higher taxonomic groups (e.g., orders) and Bayesian statistical methods to construct SSDs that reflect the richness (or perceived importance) of these groups. Here, we describe and analyze several models from a Bayesian perspective to construct SSDs from data derived using rapid toxicity testing, combining both rapid test data and expert opinion. We compare these new models with two frequentist approaches, Kaplan-Meier and a log-normal distribution, using a large data set on the salinity sensitivity of freshwater macroinvertebrates from Victoria (Australia). The frequentist log-normal analysis produced a SSD that overestimated the hazard to species relative to the Kaplan-Meier and Bayesian analyses. Of the Bayesian analyses investigated, the introduction of a weighting factor to account for the richness (or importance) of taxonomic groups influenced the calculated hazard to species. Furthermore, Bayesian methods allowed us to determine credible intervals representing SSD uncertainty. We recommend that rapid tests, expert judgements, and novel Bayesian statistical methods be used so that SSDs reflect communities of organisms found in nature.

Statistical and data reporting guidelines for the European Journal of Cardio-Thoracic Surgery and the Interactive Cardiovascular and Thoracic Surgery

As part of the peer review process for the European Journal of Cardio-Thoracic Surgery (EJCTS) and the Interactive CardioVascular and Thoracic Surgery (ICVTS), a statistician reviews any manuscript that includes a statistical analysis. To facilitate authors considering submitting a manuscript and to make it clearer about the expectations of the statistical reviewers, we present up-to-date guidelines for authors on statistical and data reporting specifically in these journals. The number of statistical methods used in the cardiothoracic literature is vast, as are the ways in which data are presented. Therefore, we narrow the scope of these guidelines to cover the most common applications submitted to the EJCTS and ICVTS, focusing in particular on those that the statistical reviewers most frequently comment on.

National risk prediction model for elective abdominal aortic aneurysm repair.

Mortality results for elective abdominal aortic aneurysm (AAA) repair are published by the Vascular Society of Great Britain and Ireland. These mortality results are not currently risk‐adjusted. The objective of this study was to develop a national risk prediction model for elective AAA repair.

Performance of the EuroSCORE Models in Emergency Cardiac Surgery

Background—Accurate risk-adjustment models are useful for clinical decision making and are important for minimizing any tendency toward risk-averse clinical practice. In cardiac surgery, emergency patients are potentially at greatest risk of inappropriate risk-averse clinical decisions. UK cardiac surgery outcomes are currently risk-adjusted with EuroSCORE models. The objective of this study was to assess the performance of the EuroSCORE models in emergency cardiac surgery. Methods and Results—The National Institute for Cardiovascular Outcomes Research database was used to identify adult cardiac surgery procedures performed in the United Kingdom between April 2008 and March 2011. A subset of procedures (July 2010–March 2011) was used for EuroSCORE II validation. The outcome measure was in-hospital mortality. Model calibration (Hosmer–Lemeshow test, calibration plots, calculation of calibration intercept and slope) and discrimination (area under receiver-operating characteristic curve [area under the curve]) were assessed. In total, 109 988 cardiac procedures at 41 hospitals were included, of which 3342 were defined as emergency procedures. Compared with performance in all cardiac surgery and nonemergency cardiac surgery, the logistic EuroSCORE and EuroSCORE II models had poorer discrimination (area under the curve, 0.703 and 0.690, respectively) and poorer calibration for emergency surgery. The EuroSCORE risk factors of female sex, chronic pulmonary disease, neurological disease, active endocarditis, unstable angina, recent myocardial infarction, and pulmonary hypertension were not identified as important risk factors for emergency cardiac surgery. Conclusions—Both EuroSCORE models demonstrated poor calibration and comparatively poor discrimination for emergency cardiac surgery. This has important implications when these models are used for clinical decision making or to adjust governance analyses.

Joint modelling of time-to-event and multivariate longitudinal outcomes: recent developments and issues

BackgroundAvailable methods for the joint modelling of longitudinal and time-to-event outcomes have typically only allowed for a single longitudinal outcome and a solitary event time. In practice, clinical studies are likely to record multiple longitudinal outcomes. Incorporating all sources of data will improve the predictive capability of any model and lead to more informative inferences for the purpose of medical decision-making.MethodsWe reviewed current methodologies of joint modelling for time-to-event data and multivariate longitudinal data including the distributional and modelling assumptions, the association structures, estimation approaches, software tools for implementation and clinical applications of the methodologies.ResultsWe found that a large number of different models have recently been proposed. Most considered jointly modelling linear mixed models with proportional hazard models, with correlation between multiple longitudinal outcomes accounted for through multivariate normally distributed random effects. So-called current value and random effects parameterisations are commonly used to link the models. Despite developments, software is still lacking, which has translated into limited uptake by medical researchers.ConclusionAlthough, in an era of personalized medicine, the value of multivariate joint modelling has been established, researchers are currently limited in their ability to fit these models routinely. We make a series of recommendations for future research needs.