M McDowall

Predicting functional outcome in acute stroke: comparison of a simple six variable model with other predictive systems and informal clinical prediction

Background: Statistical models that predict functional outcome after stroke using six simple variables (SSV) have recently been developed and validated. Objective: To compare the accuracy of these models with other simple ways of predicting outcome soon after stroke. Methods: The SSV model for being alive and independent (modified Rankin score ⩽2) six months or one year after stroke was compared with predictions based on a model that included only age and Oxford community stroke project classification, with predictions based on conscious level and urinary continence, and with informal clinical predictions made by clinicians interested in stroke. Predictions were compared in an independent hospital based cohort of stroke patients using receiver operator characteristic (ROC) curves. Results: The SSV model at six months had a significantly greater area under the curve (0.84) than the model with only age and stroke classification (0.75). Predictions based on conscious level and urinary continence were no better than those of the SSV model and were unable to predict subjects with a high probability of good outcome. The sensitivity and specificity for informal clinical predictions at one year lay on or below the SSV model curve, implying that the SSV model was at least as good as clinical predictions. Conclusions: The SSV models performed as well as or better than other simple predictive systems. These models will be useful in epidemiological studies but should not be used to guide clinical management until their impact on patient care and outcome has been evaluated.

Study of the Relationship Between Social Deprivation and Outcome After Stroke

Background and Purpose— Although the incidence and mortality of stroke are known to be inversely related to socioeconomic status (SES), the relationship between SES and recovery after stroke has been little-studied. This study has investigated the relationship between SES and case fatality, “death or dependency,” and “death or institutional care” at 6 months after stroke. Methods— Patients with acute stroke (n=2709) were identified using routine hospital discharge data and SES was measured using Carstairs scores (an ecological index of social deprivation). Case mix and treatment data were collected by medical chart review, case fatality by record linkage, and functional status and place of residence by questionnaire. Logistic regression was used to adjust the association of social deprivation and outcome for case mix and selected treatment variables. Results— With increasing social deprivation, patients were younger, more likely to live alone, and, on admission, more likely to need help to walk. Social deprivation was not associated with case fatality or with “death or institutional care” in any analysis. However, patients residing in the most deprived areas (deprivation categories 6 and 7) were significantly more likely to be dead or dependent than patients from more affluent areas. This association was weakened but remained after adjusting for case mix and treatment variables. Conclusions— These findings contribute to growing evidence of an inverse social gradient in disability after stroke. Institutionalization, as a proxy for functional outcome, may not reflect this fact. A marked social gradient in case fatality after stroke seems unlikely.

Can simple clinical features be used to identify patients with severe carotid stenosis on Doppler ultrasound

OBJECTIVES Carotid endarterectomy reduces the risk of stroke in symptomatic patients with severe ipsilateral carotid stenosis. Symptomatic patients should therefore undergo carotid Doppler imaging, but in some centres access to imaging is limited. It was therefore investigated whether simple clinical features alone or in combination could be used to identify patients with severe carotid stenosis, so that they could be referred preferentially for carotid imaging. METHODS 1041 patients with acute stroke, cerebral or retinal transient ischaemic attacks, and retinal strokes admitted to Western General Hospital or seen in neurovascular clinics were assessed by a stroke physician. Their carotid arteries were investigated using colour Doppler imaging by a consultant neuroradiologist. Patients with primary intracerebral haemorrhage, total anterior circulation strokes, posterior circulation strokes, or posterior circulation transient ischaemic attacks were excluded because carotid surgery would be inappropriate. RESULTS 726 patients were used in the analysis. Stepwise logistic regression showed that there were significant positive associations between severe carotid stenosis and an ipsilateral bruit, diabetes mellitus, and previous transient ischaemic attacks; and a negative association with lacunar events. The strategy with the highest specificity (97%) was “any three of these four features” but sensitivity was only 17%. The strategy with the highest sensitivity (99%) was to use one or more of the four features, but specificity was only 22%. CONCLUSION None of the strategies identified all patients with severe carotid stenosis with a reasonable specificity. When access to carotid imaging is severely limited, simple clinical features are of some use in prioritising patients for imaging, but access to carotid imaging should be improved.

Reliability of the variables in a new set of models that predict outcome after stroke

Objectives: To provide valid predictions of outcome, the variables included in a prognostic model must be capable of reliable collection. The authors have recently reported a set of simple but rigorously developed models that predict outcome after stroke. The aim of this study was to establish the inter-rater reliability of the variables included in the models. Methods: Inter-rater agreement was measured prospectively (between two clinicians; 92 patients) and retrospectively (between two auditors; 200 patients) and the validity of the data collected retrospectively was estimated by comparing them with data collected prospectively (195 patients). In the prospective study inter-rater agreement for urinary incontinence and for the variables of three other previously published models was also measured. The median difference (md) between ages and κ statistics for other variables was calculated. Results: For the model variables, prospective agreement ranged from good to excellent (age: md 0 years; living alone before the stroke κ 0.84; pre-stroke functional independence κ 0.67; normal verbal Glasgow Coma Scale score κ 0.79; ability to lift both arms against gravity κ 0.97; ability to walk unaided κ 0.91) while retrospective agreement (age: md 0 years; κ 0.55–0.92) and agreement between prospective and retrospective observers (age: md 0 years; κ 0.49–0.78) was acceptable but less good. Prospective agreement was excellent for urinary incontinence (κ 0.87) and variable for the other models (κ 0.23–0.81) Conclusion: The variables included in these new simple models of outcome after stroke are capable of reliable collection, comparable to or better than that of the other predictive variables considered. When collected retrospectively, the model variables are likely to remain reliable and reasonably valid.

Use of statistical process control charts in stroke medicine to determine if clinical evidence and changes in service delivery were associated with improvements in the quality of care

Background and objective: Monitoring the effect of service changes on quality of care is essential. By using statistical process control (SPC) charts, this study aimed to explore the relationship between changes in the structure of stroke services and the process of care. Methods: Prospectively acquired data on the process of acute stroke care from three hospitals admitting 2962 patients (July 2001 to June 2004) were charted retrospectively on SPC charts for individual values (I charts) to determine whether or not “special cause variation” followed known changes in stroke service structure and publication of the Medical Research Council (MRC) Heart Protection Study. Unexpected signals of special cause variation were identified and reasons for observed patterns were sought by discussion with clinical teams. Results: Improved brain imaging provision was followed by a reduction in time to imaging and earlier prescription of aspirin for ischaemic stroke. The MRC Heart Protection Study was followed by increased statin prescription. However, increasing beds allocated to stroke had no influence on the proportion of patients receiving stroke unit care. Some unexpected signals of special cause variation could be plausibly explained (eg, breakdown of brain scanner), but others could not. Anecdotal evidence from healthcare professionals suggests that charts may be acceptable in clinical practice. Conclusion: SPC charts have the potential to provide valuable insights into the impact of changes in structure of services and of clinical evidence on the process of stroke care. In the present study, the charts were generally well received by healthcare professionals.

Prevention by toxic gases

In their article on the Spanish flu pandemic seen through the BMJ ’s eyes, Jefferson and Ferroni describe several hypotheses on causality and prevention during the …