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Biomedical subjects

M McDowall

Publications and source records attributed to M McDowall.

17 recordsLinked to original sources
PubMed2004

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 < or =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.

Activities of Daily Living↗
PubMed2003

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 kappa 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 kappa 0.84; pre-stroke functional independence kappa 0.67; normal verbal Glasgow Coma Scale score kappa 0.79; ability to lift both arms against gravity kappa 0.97; ability to walk unaided kappa 0.91) while retrospective agreement (age: md 0 years; kappa 0.55-0.92) and agreement between prospective and retrospective observers (age: md 0 years; kappa 0.49-0.78) was acceptable but less good. Prospective agreement was excellent for urinary incontinence (kappa 0.87) and variable for the other models (kappa 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.

Aged↗
PubMed2002

Fractures after stroke: frequency, types, and associations.

BACKGROUND AND PURPOSE: Stroke patients may have an increased risk of fractures because of weak bones or an increased risk of falling. Our goal was to estimate the frequency of fracture after stroke and to identify those at greatest risk. METHODS: This study incorporated 2 complementary strategies: a prospective, single-center, cohort study and an analysis of Scottish routine hospital discharge data. RESULTS: Eighty-eight fractures (30% hip) occurred in 2696 hospital-referred stroke patients. The proportions sustaining any fracture or hip fracture within 2 years were 4% and 1.1%, respectively, 1.4 (95% CI, 0.92 to 2.07) times the rate of hip fracture in the general population (ie, observed number divided by expected number or standardized morbidity ratio). Female sex, older age, low abbreviated mental test score, and prestroke dependence were associated with an increased hip fracture rate. Routine data identified 129 935 acute stroke patients admitted to Scottish hospitals. During 363 447 patient-years, 4528 patients had hip fractures, 2.0% had fractures by 1 year, and 10.6% had fractures by 10 years. This is 1.7 times the rate of hip fracture in the general population and 2.3 times that in patients with myocardial infarction. Older patients predictably had the highest rate of poststroke hip fractures but a lower standardized morbidity ratio than younger patients. CONCLUSIONS: Fractures after stroke are probably frequent and serious enough to justify the development of preventive strategies, but the modest event rate would mean that randomized, controlled trials to test these strategies specifically in stroke patients would need to enroll thousands of patients.

Age Factors↗
PubMed1999

The influence of randomized trials on the use of anticoagulants for atrial fibrillation.

INTRODUCTION: Anticoagulants and anti-platelet drugs have been shown in randomized trials to reduce the risk of stroke in patients with atrial fibrillation (AF). We therefore investigated their use in patients known to be in AF before a stroke, transient ischaemic attack (either cerebral or ocular) or retinal artery occlusion to assess the influence of trials on clinical practice. METHODS: Inpatients and outpatients with acute stroke, transient ischaemic attack or retinal artery occlusion were prospectively identified by a stroke physician from 1990 to 1997. The presence or absence of AF before the vascular event, and prior use of anticoagulant and anti-platelet drugs were recorded at the time of the assessment and verified using information from general practitioner and hospital case notes. RESULTS: Of 1934 patients with stroke or retinal artery occlusion, 191 (10%) were in AF before their ischaemic event. Anticoagulants had been used in 40 (21%) of these, but only in 32 (2%) of the 1743 patients in sinus rhythm [odds ratio (OR) 14.2, 95% confidence interval (CI) 8.6-23.2]. Anti-platelet drugs had been used in 62 (32%) of those with AF compared with 500 (30%) of those in sinus rhythm (OR 1.2, 95% CI 0.9-1.64). Of the 161 patients in AF without contraindications to anticoagulants, only 36 (22%) were taking them. Although there was a statistically significant increase in anticoagulant use from 8% in 1990 to 23% in 1996, this could be explained solely by a fall in the age of the patients referred to our hospital. CONCLUSION: Anticoagulation is probably under-used in AF. We found no conclusive evidence that anticoagulation trials have influenced clinical practice. This raises issues about the dissemination and implementation of trial results.

Aged↗
PubMed1999

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.

Aged↗
PubMed1998

Is visible infarction on computed tomography associated with an adverse prognosis in acute ischemic stroke?

BACKGROUND AND PURPOSE: It is unclear whether visible infarction on a CT scan at any time after the stroke is an adverse prognostic factor once other factors such as stroke severity are taken into consideration. We examined whether visible infarction was associated with a poor outcome after stroke using univariate and multivariate analyses, including easily identifiable clinical baseline variables, and adjusting for time from stroke onset to CT. METHODS: All inpatients and outpatients with an acute ischemic stroke attending our hospital stroke service were examined by a stroke physician and entered into a register prospectively. The CT scan was coded prospectively for the site and size of any relevant recent visible infarct. The patients were followed up at 6 months to ascertain their functional status with the use of the modified Rankin Scale. Analyses of the effect of visible infarction on the outcomes "dead or dependent" or "dead" at 6 months were performed with adjustment for time from stroke to CT, clinical stroke type (lacunar, hemispheric, or posterior circulation), and in a multiple logistic regression model to adjust for confounding baseline variables such as stroke severity. RESULTS: In 993 patients in the stroke registry, visible infarction increased the risk of being dead or dependent at 6 months (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.9 to 3.3) or dead (OR, 4.5; 95% CI, 2.7 to 7.5), both on its own and after adjustment for time from stroke to CT, stroke symptoms, and other important clinical prognostic variables (OR for death or dependence in the predictive model, 1.5; 95% CI, 1.0 to 2.0; OR for death, 2.4; 95% CI, 1.4 to 4.1). CONCLUSIONS: Visible infarction on CT is an adverse prognostic indicator (albeit of borderline significance) even after adjustment for stroke severity and time lapse between the stroke and the CT scan.

Acute Disease↗
PubMed1988

Highly sensitive determination and characterization of intact cellular ester-linked phospholipids using liquid chromatography-plasma spray mass spectrometry.

Liquid chromatographic class separations of common cellular phospholipids combined with plasma spray ionization of the effluents were investigated. Comparison with true thermospray ionization involving ammonium acetate buffering revealed a gain in total ionization in the plasma spray of a factor of approximately 10 using a cation-exchange column and a solvent mixture consisting of acetonitrile-methanol-water (400:100:15, v/v). Plasma spray ionization studies of bovine brain polyphosphoinositides interrelated by the phosphate content in the inositol moiety showed almost identical monoglyceride and diglyceride ion clusters, indicating possibilities of studying the biochemical turnover of such phospholipids. Plasma spray ionization liquid chromatography-mass spectrometry of bacterial membrane phospholipids (Pseudomonas fluorescens) revealed possibilities of obtaining indications of individual fatty acid compositions from the spectra of the phosphatidylinositol and phosphatidylethanolamine fractions present. Conventional gas chromatographic fatty acid analysis agreed with the direct mass spectrometric structure elucidations. Interestingly, the two phospholipid classes had different relative fatty acid compositions with a significantly higher degree of cyclic fatty acids in the phosphatidyl ethanolamines. Plasma spray ionization yielded linear dose-response curves for both the monoglyceride and diglyceride fragment signals in the selected-ion monitoring mode. The detection limit for the monoglyceride and diglyceride species of phosphatidylcholine under the chromatographic and mass spectrometric conditions used was found to be in the picogram range.

Cell Membrane↗
PubMed1988

Maternal drug histories and congenital malformations: limb reduction defects and oral clefts.

In a case control study, prescription data were examined for the three months before the last menstrual period and for the first trimester of pregnancy in (a) 115 mothers of children with limb reduction defects, (b) 676 mothers of children with oral cleft, and (c) an equal number of control mothers of normal babies from the same doctor's practice for each case. In the limb reduction study, the study mothers were prescribed more drugs generally although this did not reach statistical significance, nor were there significant differences between study and control mothers for individual groups of drugs. In the oral cleft study, significantly more drugs were prescribed to study mothers in the three months before the last menstrual period, and a similar trend, which did not reach statistical significance, was observed in the first trimester. Anticonvulsant drugs were prescribed significantly more frequently to study mothers during the whole period of the study. A significant association was also demonstrated between oral contraceptives taken in the three months before the last menstrual period and oral cleft, but doubt must remain concerning this relationship; the risk is not well understood and is likely to be nonspecific. A number of other significant associations were identified, although their importance in practice is uncertain in view of the confounding factors that may affect a study of this kind.

Abnormalities, Drug-Induced↗
PubMed1985

Mortality from congenital malformations by mother's country of birth.

Mortality from congenital malformations by mother's country of birth was examined in England and Wales between the years 1976 and 1980, based on stillbirths and infant deaths. There were 18 870 stillbirths and infant deaths attributed to congenital malformations in this period, of which 2 375 (13%) were to mothers born outside the United Kingdom. There were excess deaths from malformations among Pakistani, Indian/Bangladeshi, African, and Irish mothers. In contrast, West Indian mothers had a consistent deficit in deaths from malformations over the study period. The significance of these findings is discussed.

Congenital Abnormalities↗
PubMed1982

Mortality of Shipham residents: 40-year follow-up.

The 1939 populations of Shipham, a village in Somerset with high soil-cadmium levels, and a nearby control village have been followed for 40 years. Death certificates were obtained for those who had died, and the mortality rates were compared with those for England and Wales. Small excesses of hypertensive, cerebrovascular, and genitourinary disease were noted in Shipman but not in the control village. These conditions have been associated wih cadmium toxicity, and so it is possible that cadmium had some influence on the disease pattern in Shipham; but if so, the effect was slight. By contrast, fewer deaths than expected from respiratory disease and cancers were observed in both villages. This gave rise to all-cause mortality rates in Shipham and the control village which were similar and well below the national average.

Cadmium Poisoning↗
PubMedDate not supplied

Adjusting proportional mortality ratios for the influence of extraneous causes of death.

Proportional mortality ratios (PMRs) are frequently used where denominators of the population at risk are not available or are known to be seriously biased. The interpretation of proportional measures requires care and can be complicated by the fact that a PMR of a cause of interest may be affected by disproportionate mortality from one or more other causes of death. This problem is examined using occupational mortality data for England and Wales. A method of allowing for the influence of other causes of death on a PMR of interest is proposed and it is argued that this approach is a useful aid to the general interpretation of PMRs.

Adolescent↗
PubMedDate not supplied

A comparison of standardized and proportional mortality ratios.

Proportional mortality analyses are traditionally considered to be unreliable because they lack information on persons at risk. Standardized mortality ratios (SMRs) are often used in preference to proportional mortality ratios ( PMRs ) even when the denominator or numerator of rates is known to be biased. Examination of data from 30 randomly selected occupational units described by the U.K. Office of Population Censuses and Surveys ( OPCS ) revealed, however, that age-standardized cause-specific SMRs and PMRs have an almost constant relationship: the ratio of the cause-specific PMR closely approximating the all-cause SMR of the group under consideration. Hence, a PMR above 100 almost always indicates that the corresponding cause-specific SMR is greater than the all-cause SMR (and vice versa). Furthermore, approximately 70 per cent of conditions with significantly high PMRs above 200 have corresponding SMRs which are also significantly high. When cautiously interpreted, the PRM may, therefore, be a useful indicator of an increased frequency of disease in a particular occupational or other group.

England↗