Recurrent events counted in evaluations of predictive accuracy

Objectives: To describe an alternate approach for the calculation of sensitivity and specificity when analyzing the accuracy of screening tools, which can be used when standard calculations may be inappropriate. Sensitivity^ER (ER denoting event rate) is the number of events correctly predicted, divided by the total number of events. Specificity^ER is the amount of time that study participants are predicted to be event negative, divided by the total amount of participant observed time. Variance estimates for these statistics are constructed by bootstrap resampling, taking into account event dependence.

Methods: Standard and alternate approaches for calculating sensitivity and specificity were applied to hospital falls risk screening tool data. In this application, the outcome of interest was a recurrent event, there were multiple applications of the screening tool, delays in screening tool  completion, and patients' follow-up durations were unequal.

Results: Application of sensitivity^ER and specificity^ER to this data not only provided a clearer description of the screening tool's overall accuracy, but also allowed examination of accuracy over time, accuracy in predicting specific event numbers, and evaluation of the added value that screening tool reapplications may have.

Conclusion: Sensitivity^ER and specificity^ER provide a valuable approach to screening tool evaluation in the clinical setting.

Design-related bias in hospital fall risk screening tool predictive accuracy evaluations: systematic review and meta-analysis.

Introduction: Fall risk screening tools are frequently used as a part of falls prevention programs in hospitals. Design-related bias in evaluations of tool predictive accuracy could lead to overoptimistic results, which would then contribute to program failure in practice.

Methods: A systematic review was undertaken. Two blind reviewers assessed the methodology of relevant publications into a four-point classification system adapted from multiple sources. The association between study design classification and reported results was examined using linear regression with clustering based on screening tool and robust variance estimates with point estimates of Youden Index (= sensitivity + specificity - 1) as the dependent variable. Meta-analysis was then performed pooling data from prospective studies.

Results: Thirty-five publications met inclusion criteria, containing 51 evaluations of fall risk screening tools. Twenty evaluations were classified as retrospective validation evaluations, 11 as prospective (temporal) validation evaluations, and 20 as prospective (external) validation evaluations. Retrospective evaluations had significantly higher Youden Indices (point estimate [95% confidence interval]: 0.22 [0.11, 0.33]). Pooled Youden Indices from prospective evaluations demonstrated the STRATIFY, Morse Falls Scale, and nursing staff clinical judgment to have comparable accuracy.

Discussion: Practitioners should exercise caution in comparing validity of fall risk assessment tools where the evaluation has been limited to retrospective classifications of methodology. Heterogeneity between studies indicates that the Morse Falls Scale and STRATIFY may still be useful in particular settings, but that widespread adoption of either is unlikely to generate benefits significantly greater than that of nursing staff clinical judgment.

Food patterns associated with blood lipids are predictive of coronary heart disease : the Whitehall II study

Analysis of the epidemiological effects of overall dietary patterns offers an alternative approach to the investigation of the role of diet in CHD. We analysed the role of blood lipid-related dietary patterns using a two-step method to confirm the prospective association of dietary pattern with incident CHD. Analysis is based on 7314 participants of the Whitehall II study. Dietary intake was measured using a 127-item FFQ. Reduced rank regression (RRR) was used to derive dietary pattern scores using baseline serum total and HDL-cholesterol, and TAG levels as dependent variables. Cox proportional hazard regression was used to confirm the association between dietary patterns and incident CHD (n 243) over 15 years of follow-up. Increased CHD risk (hazard ratio (HR) for top quartile: 2·01 (95 % CI 1·41, 2·85) adjusted for age, sex, ethnicity and energy misreporting) was observed with a diet characterised by high consumption of white bread, fried potatoes, sugar in tea and coffee, burgers and sausages, soft drinks, and low consumption of French dressing and vegetables. The diet-CHD relationship was attenuated after adjustment for employment grade and health behaviours (HR for top quartile: 1·81; 95 % CI 1·26, 2·62), and further adjustment for blood pressure and BMI (HR for top quartile: 1·57; 95 % CI 1·08, 2·27). Dietary patterns are associated with serum lipids and predict CHD risk after adjustment for confounders. RRR identifies dietary patterns using prior knowledge and focuses on the pathways through which diet may influence disease. The present study adds to the evidence that diet is an important risk factor for CHD.

Examination of EMG normalisation methods for the study of the posterior and posterolateral neck muscles in healthy controls

The purpose of this study was to examine the reliability of normalisation methods used in the study of the posterior and posterolateral neck muscles in a group of healthy controls. Six asymptomatic male subjects performed a total of 12 maximum voluntary isometric contractions (MVIC) and 60%-submaximal isometric contractions (60%-MVIC) against the torque arm of an isokinetic dynamometer whilst surface and intramuscular electromyography (EMG) was recorded unilaterally from representative posterior and posterolateral locations. Reliability was calculated using intra-class correlation coefficient (ICC), relative standard error of measurement (%SEM) and relative coefficient of variation (%CV). Maximal torque output was found to be highly reliable in the directions of extension and right lateral bending when the first of three MVIC contractions was excluded. When averaged across contraction direction, high reliability was found for both surface (MVIC: ICC = 0.986, %SEM = 7.5, %CV = 9.2; 60%-MVIC: ICC = 0.975, %SEM = 10, %CV = 13.7) and intramuscular (MVIC: ICC = 0.910, %SEM = 20, %CV = 19.1; 60%-MVIC: ICC = 0.952, %SEM = 16.5, %CV = 13.5) electrodes. Intramuscular electrodes displayed the least reliability in right lateral bending. The use of visual feedback markedly increased the reliability of 60%-MVIC contractions.

Predictive modeling of student competency

Explores how machine learning techniques can be used to build effective student modeling systems with constrained development and operational overheads, by integrating top-down and bottom-up initiatives. Emphasizes feature-based modelling.

The accounting professional of the future : never mind the quality check the look!

Using legitimacy theory this paper contrasts the values portrayed by public accounting firms via their recruitment practices and society's expectations of the responsibilities of a professional accountant. Society confers on organisations legitimacy when the value system of the organisation is congruent with the value system of the larger social system (Deegan, 2006). It is argued that there is increasing incongruence between the value system of public accounting firms (that employ accounting graduates) and society's value system that includes an expectation of accountants to act in the public interest. This study draws on evidence from recent corporate collapses, to question whether the attributes/skills displayed by accountants have reduced their capacity to act in the public interest. Interviews with employers show that preferences for employment are given to graduates who 'fit the culture' of the organisation and have the ability to 'market' the firm to clients. Attributes that define the professional accountant appear to be less highly valued. It is concluded that the attributes valued in the workplace today have the potential to increase the risk of 'severing the social contract' between the accounting profession and society.

Relative deprivation between neighbouring wards is predictive of coronary heart disease mortality after adjustment for absolute deprivation of wards

Background The aims of this study were to assess whether deprivation inequality at small area level in England is associated with coronary heart disease (CHD) mortality rates and to assess whether this provides evidence of an association between area-level and individual-level risk.

Methods Mortality rates for all wards in England were calculated using all CHD deaths between 2001 and 2006. Ward-level deprivation was measured using the Carstairs Index. Deprivation inequality within local authorities (LAs) was measured by the IQR of deprivation for wards within the LA. Relative deprivation for wards was measured as the modulus of the difference between deprivation for the ward and average deprivation for all neighbouring wards.

Results Deprivation inequality within LAs was positively associated with CHD mortality rates per 100 000 (eg, all men β; 95% CI=2.7; 1.1 to 4.3) after adjustment for absolute deprivation (p<0.001 for all models). Relative deprivation for wards was positively associated with CHD mortality rates per 100 000 (eg, all men 1.4; 0.7 to 2.1) after adjustment for absolute deprivation (p<0.001 for all models). Subgroup analyses showed that relative deprivation was independently associated with CHD mortality rates in both affluent and deprived wards.

Conclusions Rich wards surrounded by poor areas have higher CHD mortality rates than rich wards surrounded by rich areas, and poor wards surrounded by rich areas have worse CHD mortality rates than poor wards surrounded by poor areas. Local deprivation inequality has a similar adverse impact on both rich and poor areas, supporting the hypothesis that income inequality of an area has an impact on individual-level health outcomes.