Receiver operating characteristic plot and area under the curve with binary classifiers: pragmatic analysis of cognitive screening instruments

Case-control study developing Scottish Epilepsy Deaths Study Score to predict epilepsy-related death

This study aimed to develop a risk prediction model for epilepsy-related death in adults. In this age- and sex-matched case-control study, we compared adults (aged ≥16 years) who had epilepsy-related death between 2009 and 2016 to living adults with epilepsy in Scotland. Cases were identified from validated administrative national datasets linked to mortality records. ICD-10 cause-of-death coding was used to define epilepsy-related death. Controls were recruited from a research database and epilepsy clinics. Clinical data from medical records were abstracted and used to undertake univariable and multivariable conditional logistic regression to develop a risk prediction model consisting of four variables chosen a priori. A weighted sum of the factors present was taken to create a risk index-the Scottish Epilepsy Deaths Study Score. Odds ratios were estimated with 95% confidence intervals (CIs). Here, 224 deceased cases (mean age 48 years, 114 male) and 224 matched living controls were compared. In univariable analysis, predictors of epilepsy-related death were recent epilepsy-related accident and emergency attendance (odds ratio 5.1, 95% CI 3.2-8.3), living in deprived areas (odds ratio 2.5, 95% CI 1.6-4.0), developmental epilepsy (odds ratio 3.1, 95% CI 1.7-5.7), raised Charlson Comorbidity Index score (odds ratio 2.5, 95% CI 1.2-5.2), alcohol abuse (odds ratio 4.4, 95% CI 2.2-9.2), absent recent neurology review (odds ratio 3.8, 95% CI 2.4-6.1) and generalized epilepsy (odds ratio 1.9, 95% CI 1.2-3.0). Scottish Epilepsy Deaths Study Score model variables were derived from the first four listed before, with Charlson Comorbidity Index ≥2 given 1 point, living in the two most deprived areas given 2 points, having an inherited or congenital aetiology or risk factor for developing epilepsy given 2 points and recent epilepsy-related accident and emergency attendance given 3 points. Compared to having a Scottish Epilepsy Deaths Study Score of 0, those with a Scottish Epilepsy Deaths Study Score of 1 remained low risk, with odds ratio 1.6 (95% CI 0.5-4.8). Those with a Scottish Epilepsy Deaths Study Score of 2-3 had moderate risk, with odds ratio 2.8 (95% CI 1.3-6.2). Those with a Scottish Epilepsy Deaths Study Score of 4-5 and 6-8 were high risk, with odds ratio 14.4 (95% CI 5.9-35.2) and 24.0 (95% CI 8.1-71.2), respectively. The Scottish Epilepsy Deaths Study Score may be a helpful tool for identifying adults at high risk of epilepsy-related death and requires external validation.

Accuracy of cognitive screening instruments reconsidered: overall, balanced or unbiased accuracy?

Aim: To examine three different accuracy metrics for evaluation of cognitive screening instruments: overall correct classification accuracy (Acc), the sum of true positives and negatives divided by the total number tested; balanced accuracy (balanced Acc), half of the sum of sensitivity and specificity; and unbiased accuracy (unbiased Acc), removing biasing effects of random associations between test results and disease prevalence. Materials & methods: Data from a prospective test accuracy study of Mini-Addenbrooke's Cognitive Examination were used to calculate and plot the Acc measures. Results: Each Acc metric resulted in a similar pattern of results across the range of Mini-Addenbrooke's Cognitive Examination cut-offs for diagnosis of both dementia and mild cognitive impairment. Acc and balanced Acc gave more optimistic outcomes (closer to possible maximum value of 1) than unbiased Acc. Conclusion: Unbiased Acc may have advantages over Acc and balanced Acc by removing biasing effects of random associations between test result and disease prevalence.

Intracranial bruit: Charles Warlow's challenge revisited

Over 20 years ago, Charles Warlow, the founding editor of Practical Neurology, offered a copy of his stroke textbook to anyone diagnosing an intracranial arteriovenous malformation by auscultation of the skull alone. This article examines the possible diagnostic value of intracranial bruit in terms of the 2×2 contingency table for diagnostic tests and recounts an historical case.