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Biomedical subjects

S C Lewis

Publications and source records attributed to S C Lewis.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1999

Can stroke physicians and neuroradiologists identify signs of early cerebral infarction on CT?

Doctors managing acute stroke are expected to recognise signs of early infarction on CT before choosing thrombolytic treatment, according to recent trials and guidelines. The ability of 13 physicians and two neuroradiologists to recognise early infarct signs and decide whether patients should be randomised in a hypothetical stroke treatment trial was tested. Only 65% of the CT scans from 14 stroke patients were correctly identified as normal or abnormal (95% CI 60-69%). Neither observer experience nor knowledge of symptoms significantly improved recognition of abnormality, although experience did significantly improve the observers' ability to reproduce their results. Parenchymal hypodensity was the least well recognised sign. Only 45% (95% CI 40%-50%) of patients were identified correctly for the hypothetical acute stroke treatment trial. Early infarction on CT is not well recognised even by experienced doctors. Part of the problem may be in understanding the definitions of the extent of infarction. These difficulties should be considered in the design of acute stroke treatment trials and in the introduction of any new acute stroke treatments.

Cerebral Infarction↗
PubMed1999

Should computed tomography appearance of lacunar stroke influence patient management?

Patients with a lacunar stroke syndrome may have cortical infarcts on brain imaging rather than lacunar infarcts, and patients with the clinical features of a small cortical stroke (partial anterior circulation syndrome, PACS) may have lacunar infarcts on imaging. The aim was to compare risk factors and outcome in lacunar syndrome (LACS) with cortical infarct, LACS with lacunar infarct, PACS with cortical infarct, and PACS with lacunar infarct to determine whether the clinical syndrome should be modified according to brain imaging. As part of a hospital stroke registry, patients with first ever stroke from 1990 to 1998 were assessed by a stroke physician who assigned a clinical classification using clinical features only. A neuroradiologist classified recent clinically relevant infarcts on brain imaging as cortical, posterior cerebral artery territory or lacunar. Of 1772 first ever strokes, there were 637 patients with PACS and 377 patients with LACS who had CT or MRI. Recent infarcts were seen in 395 PACS and 180 LACS. Atrial fibrillation was more common in PACS with cortical than lacunar infarcts (OR 2.3, 95% confidence interval (95% CI) 0.9-5.5), and in LACS with cortical than lacunar infarcts (OR 3.9, 1.2-12). Severe ipsilateral carotid stenosis or occlusion was more common in PACS with cortical than lacunar infarcts (OR 3.5, 1.3-9.5); and in LACS with cortical than lacunar infarcts (OR 3.7, 1.1-12). In conclusion, patients with cortical infarcts are more likely to have severe ipsilateral carotid stenosis or atrial fibrillation than those with lacunar infarcts irrespective of the presenting clinical syndrome. Brain imaging should modify the clinical classification and influence patient investigation.

Brain↗
PubMed1999

Why do Italian stroke patients receive CT scans earlier than UK patients? International Stroke Trial Collaborators in Italy and the UK.

Computed tomography (CT) scanning is important prior to acute stroke treatment. We wished to identify factors associated with being able to obtain a CT scan quickly, from a recent large stroke treatment trial. A questionnaire survey on the organisation of CT scanning services for stroke was sent to 179 UK and Italian hospitals who had randomised patients into the International Stroke Trial and performed at least one pre-randomisation CT scan. Data from the questionnaire were analysed in conjunction with other patient data. Italian doctors expected the CT scans to be done more quickly than UK doctors, their hospitals were more likely to have a CT scanner operating all the time, and a porter was used less frequently to take the patient to the CT scanner. A few simple changes in the way CT scanning is organised for stroke patients in the UK could speed access to CT considerably.

Cerebrovascular Disorders↗
PubMed1998

Pilot study to estimate survivors to 1995 of 1983-1984 prevalent hepatitis C infections in Lothian patients who tested positive or negative for hepatitis B surface antigen in 1983-1984.

OBJECTIVE: To estimate Hepatitis C prevalence in 1983-1984, and survivorship to 1 January 1995, of patients who tested were for Hepatitis B surface antigen in 1983-1984; and to do so according to risk of blood-borne virus transmission, including injector status. SETTING: Regional Virus Laboratory in Edinburgh. SAMPLES: Sera from 1983-1984 which were originally received for hepatitis B surface antigen testing and were classified as being at high, medium, or low risk for blood-borne virus transmission. RESULTS: Available 1983-1984 sera were tested from: (i) all 246 patients aged 15-55 years who were Hepatitis B surface antigen positive in 1983-1984; and (ii) a 10% systematic sample of 355 patients aged 15-55 years who had tested Hepatitis B surface antigen negative in 1983-1984. Patients' survival status at 1 January 1995 was established via the records of the Registrar General for Scotland. A Hepatitis C prevalent case cohort of 500 survivors to 1 January 1995- who were already infected with Hepatitis C in 1983-1984--could be established from group (i) and high or medium risk group (ii) patients with, as controls, 1460 individuals of similar age and risk group whose 1983-1984 sample was negative when tested retrospectively for Hepatitis C antibodies. Two hundred out of these 500 cases are not known to be injecting drug users, and the total would rise to 300 out of 600 if the case cohort were expanded to include low risk group (ii) surviving patients who were Hepatitis C antibody positive in 1983-1984. Between 82% (40/49) and 97% of injectors (57/59 if also HIV-infected) who were Hepatitis B surface antigen positive in 1983-1984 were already Hepatitis C antibody positive; and 72% (95% confidence interval (CI) 51%-93%) of injectors who were Hepatitis B surface antigen negative in 1983-1984 were nonetheless infected with Hepatitis C. Known drug user/contacts (excluding the major group of 59 identified HIV-infecteds) had Hepatitis C prevalence in 1983-1984 of 79% (53/67, with 95% CI 69%-89%), substantially higher than our prior assumption, which was 50%. Hepatitis C prevalence in 1983-1984 for patients who were not known to be injectors, were Hepatitis B surface antigen negative and were rated as moderate risk for blood-borne virus transmission was 13% (95% CI 4%-23%) and 8% (95% CI 3%-14%) even for low risk patients. Deaths by end December 1994 in 1983-1984 prevalent Hepatitis C infections were low: 2/35 (6%) for patients who were Hepatitis B surface antigen negative in 1983-1984 and 2/40 (5%) for Hepatitis B surface antigen positive injectors who were not HIV-infected. The latter rate with upper 95% confidence limit of 12% is modest when compared to the 10% mortality that would be expected of injectors over 11 years. CONCLUSION: Retrospective Hepatitis C testing of 1700 stored sera from high or medium risk group (ii) patients who were not known to be injectors will identify an estimated 200 (11.7%) who were already Hepatitis C infected in 1983-1984 and still alive on 1 January 1995. Retrospective Hepatitis C testing of 1300 low risk samples is expected to yield 100 (7.6%) apparently non-injector patients who were already Hepatitis C infected in 1983-1984 and still alive on 1 January 1995.

Adolescent↗
PubMed1998

Early mortality of undiagnosed but prevalent (in 1983-1984) HIV infection in Lothian injectors who tested hepatitis B surface antigen positive (group A) or negative but were high risk for blood-borne virus transmission (group B) in 1983-1984.

OBJECTIVE: To estimate the early death-rate in HIV infected injectors whose HIV infection was during the injection-related HIV outbreak in Lothian region in Scotland in 1983-1984, which was coincident with Hepatitis B transmissions. SETTING: Regional Virus Laboratory in Edinburgh. SAMPLES: Sera from 1983-1984, originally received for Hepatitis B surface antigen testing, from individuals aged 15-55 years who were positive for Hepatitis B surface antigen in 1983-1984 (group A: census) or tested negative but were at high risk for blood-borne virus transmission according to their reason for testing (group B: 50% sample). METHODS: Survival status of individuals in groups A and B who had not been diagnosed with HIV disease by the end of December 1995 was checked against the deaths' records of the Registrar General for Scotland. Stored sera from 1983-1984 for patients who had died early (that is: in 1983-1984) were tested anonymously for HIV and Hepatitis C antibodies; and prior to testing, causes of death were scored by RPB according to the likelihood of their being HIV or drugs related. RESULTS: Three early deaths were found in group A patients who were not known to be HIV infected. None of the deaths was likely to be HIV-related; the sera were not tested in order not to risk deductive disclosure. Twenty-four early deaths were found in group B patients who were not known to be HIV-infected, five of whom were both HIV and Hepatitis C antibody positive, and one other was HIV antibody negative but Hepatitis C positive. Reclassification after unlinked anonymous testing and multiplying up of the group B results (to account for 50% sample) gave the early death rate (that is: in 1983-1986) as 15/155 (10%) for HIV-infected drug users (95% CI: 6%-13%). CONCLUSION: Injection-related outbreaks of HIV infection in Lothian in 1983-1984 and at Glenochil Prison in 1993 were each associated with substantial--estimated 10%--early death-rate in HIV-infected injectors. Both HIV outbreaks were coincident with Hepatitis B transmissions, which may be relevant. Further investigations of the death-rate within 2 years of HIV infection are warranted in other exposure categories than injection-related and for injectors who have been immunized against Hepatitis B.

Adolescent↗
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↗
PubMed1998

Studies of acute ischemic stroke with proton magnetic resonance spectroscopy: relation between time from onset, neurological deficit, metabolite abnormalities in the infarct, blood flow, and clinical outcome.

BACKGROUND AND PURPOSE: Proton magnetic resonance spectroscopy (MRS) can be used to study metabolite abnormalities in the brains of stroke patients. We have used it to examine the relations between the metabolites in the infarct (N-acetylaspartate [NAA] and lactate) and the time lapse from stroke to MRS, the presenting neurological deficit, infarct size and swelling (on MRI), blood flow to the infarct (estimated by transcranial Doppler ultrasound), and clinical outcome. METHODS: Patients with symptoms of a moderate to large cortical infarct underwent serial proton MRS (Siemens 1.5 Magnetom) within 4 days, from 5 to 10, and from 11 to 35 days after the stroke. A long echo time PRESS single voxel or chemical shift imaging acquisition was used. Transcranial Doppler ultrasound was performed daily in the first week and twice per week thereafter until the final MRS. Clinical features and baseline demographic data were collected independently by a stroke physician and 6-month outcome by postal questionnaire. RESULTS: Fifty patients underwent at least 1 MRS examination. Reduced NAA in the infarct within the first 4 days was related to the clinical stroke syndrome, more extensive infarction, more severely reduced blood supply to the infarct, and the presence of lactate. The presence of lactate was related to large infarcts and reduced NAA. Swelling in the infarct was most closely associated with large infarcts and reduced blood supply but not reduced NAA or the presence of lactate. Clinical outcome was most closely related to the extent of the infarct (more than to the clinical syndrome)--the larger the infarct the worse the outcome--but not to the metabolite concentrations alone. CONCLUSIONS: The reduction in NAA (but not the presence of lactate) in a visible infarct was related to the reduction in blood flow to the infarct, which in turn was related to infarct extent and clinical outcome.

Acute Disease↗
PubMed1997

Harm reduction measures and injecting inside prison versus mandatory drugs testing: results of a cross sectional anonymous questionnaire survey. The European Commission Network on HIV Infection and Hepatitis in Prison.

OBJECTIVES: (a) To determine both the frequency of injecting inside prison and use of sterilising tablets to clean needles in the previous four weeks; (b) to assess the efficiency of random mandatory drugs testing at detecting prisoners who inject heroin inside prison; (c) to determine the percentage of prisoners who had been offered vaccination against hepatitis B. DESIGN: Cross sectional willing anonymous salivary HIV surveillance linked to a self completion risk factor questionnaire. SETTING: Lowmoss prison, Glasgow, and Aberdeen prison on 11 and 30 October 1996. SUBJECTS: 293 (94%) of all 312 inmates at Lowmoss and 146 (93%) of all 157 at Aberdeen, resulting in 286 and 143 valid questionnaires. MAIN OUTCOME MEASURES: Frequency of injecting inside prison in the previous four weeks by injector inmates who had been in prison for at least four weeks. RESULTS: 116 (41%) Lowmoss and 53 (37%) Aberdeen prisoners had a history of injecting drug use but only 4% of inmates (17/395; 95% confidence interval 2% to 6%) had ever been offered vaccination against hepatitis B. 42 Lowmoss prisoners (estimated 207 injections and 258 uses of sterilising tablets) and 31 Aberdeen prisoners (229 injections, 221 uses) had injected inside prison in the previous four weeks. The prisons together held 112 injector inmates who had been in prison for more than four weeks, of whom 57 (51%; 42% to 60%) had injected in prison in the past four weeks; their estimated mean number of injections was 6.0 (SD 5.7). Prisoners injecting heroin six times in four weeks will test positive in random mandatory drugs testing on at most 18 days out of 28. CONCLUSIONS: Sterilising tablets and hepatitis B vaccination should be offered to all prisoners. Random mandatory drugs testing seriously underestimates injector inmates' harm reduction needs.

Cross-Sectional Studies↗
PubMed1995

Attitudinal survey of adverse drug reaction reporting by medical practitioners in the United Kingdom.

1. Attitudes of doctors to the Committee on Safety of Medicines' (CSM) adverse drug reaction (ADR) reporting scheme were investigated in order to assess their understanding of the purposes of the scheme and to identify reasons for failing to report suspected adverse drug reactions. 2. A postal questionnaire and letter of invitation were sent to 500 doctors who were randomly selected from the 1992 Medical Directory. A reminder letter and a second copy of the questionnaire were sent to non-responders after 4 weeks. 3. 284 (57%) responded to the questionnaire. Of these, 179 (63%) stated that they had previously reported an ADR to the CSM or a pharmaceutical manufacturer. 77% of general practitioners stated that they had reported one or more ADRs compared with 55% of hospital doctors. 4. Reasons for under-reporting included lack of time, lack of report forms and the misconception that absolute confidence in the diagnosis of an adverse reaction was important in the decision to send in a report. 5. An investigation of seven commonly proposed reasons for under-reporting showed that on the whole they did not apply. 6. Most doctors knew the types of reactions that the Committee on Safety of Medicines seeks reports for but only 38% knew the precise meaning of the Committee on Safety of Medicines' black triangle symbol. There also seemed to be confusion about some of the purposes of the adverse drug reaction reporting scheme. 7. The number of reporting doctors is much higher than has previously been estimated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adverse Drug Reaction Reporting Systems↗
PubMed1995

Subchronic feeding study of four white mineral oils in dogs and rats.

Subchronic 90-day feeding studies were conducted on four highly refined white mineral oils to determine any potential for toxicity in Long-Evans rats (20 per sex per dose level) and beagle dogs (4 per sex per dose level). Each oil was fed at dietary dose levels of 300 ppm and 1500 ppm (w/w). No treatment-related effects of toxicological importance were detected in daily observations of general health or in periodic assessments of food consumption and body weight, hematology, serum clinical chemistry, and urinalysis. Observations in dogs suggested that the white oils produced mild laxative effects. Gross and histopathologic examinations, as well as measurements of organ weights, did not reveal any macroscopic or microscopic changes which could be due to treatment. In addition, special staining by Oil Red O of liver, mesenteric lymph nodes, spleen, gastrointestinal tract, stomach, and kidneys indicated no evidence of oil or lipid deposition. A special re-examination of tissues from female and male rats, in response to more recent conflicting data from the Fischer 344 strain, found no histopathologic signs of macrophage accumulation and/or microgranuloma formation in liver, spleen, or mesenteric lymph nodes. These data indicate that repeated exposure to relatively high levels of white mineral oils in the diets does not produce significant subchronic toxicity in Long-Evans rats or beagle dogs.

Animals↗
PubMed1993

Meconium testing for cocaine metabolite: prevalence, perceptions, and pitfalls.

OBJECTIVES: We determined the prevalence of prenatal cocaine use in a racially mixed sample of urban and suburban mothers and correlated its use with maternal demographics and newborn measurements. STUDY DESIGN: Meconium from 621 consecutive newborns delivered at two university-affiliated urban hospitals were assayed for benzoylecgonine. Maternal and infant characteristics were linked anonymously with the results. Statistical analysis included t test, Fisher's exact test, Duncan's multiple range analysis, and analysis of covariance, with a value of p < 0.05 considered significant. RESULTS: We found that 3.4% of meconium samples had benzoylecgonine levels exceeding 0.1 micrograms/ml. Its presence was statistically correlated with maternal and neonatal characteristics. A nurse's opinion of cocaine use was correct 22% of the time. CONCLUSIONS: Prenatal cocaine use was statistically associated with multiparity, multigravidity, late-onset and clinic-based prenatal care, public assistance, nonwhite race, and low academic achievement. A nurse's opinion was a poor predictor of maternal cocaine use. Cocaine-exposed infants were significantly smaller, and this correlated best with nonwhite background.

Birth Weight↗
PubMed1992

Developmental toxicity of dimethylformamide in the rat following inhalation exposure.

Dimethylformamide (DMF) is a widely used industrial solvent. DMF has been reported to be a developmental toxin when given to rodents by injection or following dermal administration. In this study, groups of pregnant rats were exposed by inhalation to either 0 (control), 30, or 300 ppm DMF from gestation day 6 through 15. In the 300 ppm rats, both maternal weight gain during gestation and fetal weights were lower than those of the controls. Fetal resorptions were not increased in this group. No significant differences among either maternal or fetal rats were seen in the 30 ppm group compared to controls. Both fetal and maternal toxicity were noted at 300 ppm and the no observed effect level under these experimental conditions was 30 ppm for both the dams and the conceptuses. DMF did not produce malformations in the rat fetus even at a level that was toxic to the dam.

Abnormalities, Drug-Induced↗
PubMed1990

Estimation of epidermal carcinogenic potency.

This report compared two statistical methods of estimating tumor latency, the Weibull distribution model and the Kaplan-Meier method. Parallelism of dose-response curves of different materials and quantitative reproducibility of dermal carcinogenesis data were also examined. The Weibull method has the advantage of producing parameter estimates, even when tumor yield is low. The Kaplan-Meier method, on the other hand, is free of distribution assumptions. Overall, since the comparisons of potency are made on the basis of parameters from the same assumed distribution on the same strain of animal, the Weibull estimates are favored. A comparison of dose-response data for benzo[a]pyrene and catalytically cracked clarified oil indicated that the slopes of the two dose-response curves were significantly different. Thus the relative carcinogenic potencies of different materials vary with dose, and potency comparisons must necessarily be dose-specific. The quantitative reproducibility of dermal carcinogenesis bioassays was also assessed. The dose-response curves from the three studies of one material had significantly different slopes. Thus the results suggested that there were sources of biological variability which could contribute to experimental error.

Animals↗
PubMed1990

A scheme for classifying carcinogens.

We present a scheme for classifying chemical carcinogens according to the weight of the evidence that each substance poses a human cancer hazard. The approach represents a logical extension of and builds upon those previously developed by the International Agency for Research on Cancer, the U.S. Environmental Protection Agency, and the so-called Tripartite Group of industrial scientists. It takes into account new scientific knowledge about chemical carcinogenesis and animal models. Eight categories are presented: known human carcinogen (Category 1), carcinogenic activity in animals, probable human carcinogen (Category 2), possible human carcinogen (Category 3), equivocal evidence for carcinogenic activity (Category 4), evidence inadequate for classification (Category 5), carcinogenic activity in animals; probably not a human cancer hazard (Category 6), carcinogenic activity in animals; considered not a human cancer hazard (Category 7), evidence of noncarcinogenicity (Category 8). Evidence useful for categorization includes human studies, animal bioassays, corroborative evidence from bioassays, and mechanistic studies relevant to determining the predictivity of animal responses for human hazard. Weighing this evidence to derive a conclusion about classification is a process that requires expert judgment; it cannot now be reduced to a simple set of decision rules. However, we identify the kinds of information that can be useful in this process, and indicate how each might most appropriately be used.

Animals↗