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Biomedical subjects

A Algra

Publications and source records attributed to A Algra.

At least 109 records · Page 6Linked to original sources
PubMed2000

[Prevalence and treatment of hypercholesterolemia in patients with manifest vascular disease according to practice guidelines of the current cholesterol consensus].

OBJECTIVE: To determine the prevalence of hypercholesterolaemia and the use of lipid-lowering medication in patients with a manifest vascular disease. DESIGN: Prospective, cross-sectional. METHODS: In patients who visited the University Medical Centre Utrecht, the Netherlands, for the first time with a manifestation of atherosclerosis in the period 1 September 1996-15 November 1998, we determined by a single measurement of the cholesterol if they were eligible for lipid-lowering medication according to the cholesterol cut-off value mentioned in the new Dutch cholesterol guidelines (1998) of the Dutch Institute for Health Care Improvement. RESULTS: The study group comprised 737 patients: 539 (73%) males and 198 (27%) females, with a mean age of 62 year. 500 (68%) were eligible for lipid-lowering treatment. 66 patients (9%) were being treated according to the guidelines and in 106 (14%) the aim of a cholesterol lower than 5.0 mmol/1 was not reached despite cholesterol lowering medication. In 328 patients (45%) hyperlipidaemia was not treated pharmacologically. CONCLUSION: Two-thirds of the patients with manifest vascular disease had hypercholesterolaemia. Many of these patients were not yet being treated.

Aged↗
PubMed2000

Long-term survival after valve replacement with Björk-Shiley CC valves. Björk-Shiley Study Group.

Information on the life expectancy of Bjork-Shiley convexo-concave (BScc) valve recipients is necessary when considering prophylactic replacement. However, little is known about the late results after valve replacement with BScc valves. We describe long-term survival and its determinants of the Dutch BScc cohort and compare mortality figures with those of the general population and those used in guidelines for prophylactic replacement. Follow-up was obtained on all Dutch BScc valve recipients (n = 2,264) (end of study 1996). Survival over a 15-year period and its determinants were described using the Kaplan-Meier product-limit method and Cox regression, respectively. Standardized mortality ratios (SMRs) were used to compare mortality rates of BScc valve recipients who survived at least 30 days after surgery with the Dutch population rates. Survival at 15 years for aortic, mitral, and double valve recipients was 55.0% (95% confidence interval [CI] 51.9 to 58.1), 40.8% (95% CI 37.1 to 44.4), and 38.6% (95% CI 33.2 to 43.9), respectively. The determinants of survival were patient, history, and procedure related. The SMR for all BScc valve recipients was 4.2 (95% CI 3.4 to 5.2) in the first year of follow-up, after which it decreased to 2.0 (95% CI 1.8 to 2.3) and remained constant until the 14th year. SMRs depended on time since implantation, age at the time of implantation, and position of the valve replaced. Most of life expectancy estimates in prophylactic replacement guidelines of BScc valves underrate the true survival estimates. Age, valve position, and time- specific risks of death after valvular surgery should be accounted for. Different excess mortality rates should be applied for patients from different age groups: the older the patient the lower the excess.

Aortic Valve↗
PubMed2000

Randomized pilot trial of postoperative aspirin in subarachnoid hemorrhage.

OBJECTIVE: To assess the safety and feasibility of a clinical trial on the effectiveness of acetylsalicylic acid (ASA) in subarachnoid hemorrhage (SAH). BACKGROUND: Several studies have indicated that increased platelet activity might be involved in the pathogenesis of delayed cerebral ischemia (DCI) after SAH. METHOD: Fifty patients who had early surgery (< or =4 days) for a ruptured aneurysm were enrolled in this randomized, double-blind, placebo-controlled trial. Trial medication, consisting of suppositories with 100 mg ASA versus placebo, was started immediately after surgical clipping of the aneurysm and continued for 21 days. End points were functional outcome and quality of life at 4 months, clinical deterioration after operation, development of DCI, hypodense lesion on postoperative CT, and hemorrhagic complications. RESULTS: One-third of all patients with aneurysmal SAH were eligible for the trial. Fifteen of 26 patients receiving placebo deteriorated clinically versus 10 of 24 patients receiving ASA; 4 patients in each group deteriorated from DCI. Postoperative hypodensities on CT were observed in 27 patients, distributed equally in both groups. Functional outcome and quality-of-life scores were slightly in favor of patients who had received ASA, but not to a significant degree (p = 0.22). Two patients in the ASA group had an asymptomatic hemorrhagic complication, and one patient in the placebo group had a fatal and another a symptomatic hemorrhagic complication. CONCLUSION: This pilot study shows that a clinical trial of acetylsalicylic acid (ASA) in subarachnoid hemorrhage (SAH) is feasible and probably safe. The effectiveness of ASA on functional outcome and delayed cerebral ischemia has to be studied in a larger trial.

Aspirin↗
PubMed2000

Calcium antagonists for aneurysmal subarachnoid haemorrhage.

BACKGROUND: Rupture of an intracranial aneurysm causes bleeding into the subarachnoid space, which may lead to spasm of the cerebral arteries and ischaemic damage to the brain. Prophylactic use of calcium antagonists in patients with ruptured intracranial aneurysms might reduce the risk of ischaemic damage. OBJECTIVES: This review aimed to determine whether calcium antagonists improve outcome in patients with aneurysmal subarachnoid haemorrhage (SAH). SEARCH STRATEGY: The Cochrane Stroke Group trials register (last searched: March 1999) plus hand searching and personal contacts with trialists and pharmaceutical companies marketing calcium antagonists. SELECTION CRITERIA: All completed, unconfounded, truly randomised controlled trials comparing any calcium antagonist with control, within ten days of SAH onset. Eleven trials that met the inclusion criteria were included in the overview. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed trial quality. Trialists were contacted to obtain missing information. MAIN RESULTS: We analysed 11 trials totalling 2804 randomized patients with subarachnoid haemorrhage (1376 in the treatment and 1428 in the control group). The drugs analyzed were: nimodipine (eight trials, 1574 patients), nicardipine (two trials, 954 patients), and AT877 (one trial, 276 patients). In 92% of the patients aneurysms were confirmed by angiography or autopsy. Overall, calcium antagonists significantly reduce the risk of poor outcome after subarachnoid haemorrhage: relative risk (RR) 0.82 (95% CI 0. 72-0.93); the absolute risk reduction was 5.1%, the corresponding number of patients needed to treat to prevent a single poor outcome event is 20. For oral nimodipine alone the RR was 0.69 (0.58-0.84). The RR of death on treatment with calcium antagonists was 0.94 (95% CI 0.80-1.10), that of ischaemic neurological deficits 0.67 (95% CI 0.59-0.76), and that of CT-scan documented cerebral infarction 0.80 (95% CI 0.71-0.89). REVIEWER'S CONCLUSIONS: Calcium antagonists reduce the proportion of patients with poor outcome and ischemic neurological deficits after aneurysmal SAH; the risk reduction for case fatality alone is not statistically significant. The results for 'poor outcome' are statistically robust, but depend mainly on trials with oral nimodipine; the evidence for nicardipine and AT877 is inconclusive. The intermediate factors through which nimodipine exerts its beneficial effect after aneurysmal SAH remain uncertain.

Calcium Channel Blockers↗
PubMed2000

Circulatory volume expansion for aneurysmal subarachnoid hemorrhage.

BACKGROUND: Patients with subarachnoid haemorrhage who develop spasm of the cerebral arteries may suffer from delayed cerebral ischaemia. This may be exacerbated by reduced circulatory volume. Intravenous fluid therapy to expand the circulating volume might reduce the risk of delayed cerebral ischaemia and so reduce the risk of neurological disability. OBJECTIVES: The object of this review was to determine whether there is evidence that volume expansion therapy improves outcome in patients with aneurysmal subarachnoid haemorrhage. SEARCH STRATEGY: The Cochrane Stroke Group's Specialised Register was searched for trials relevant to this review (last searched: March 1999). Trialists were also contacted. SELECTION CRITERIA: All randomized controlled trials of volume expansion therapy in patients with aneurysmal subarachnoid haemorrhage. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted the data and assessed trial quality. Trialists were contacted to obtain missing information. MAIN RESULTS: Two trials were identified. For one trial the decision about inclusion is pending because clinical data on follow up have not been provided yet. In the other trial, outcome assessment was done at the day of operation (7 to 10 days after subarachnoid haemorrhage); data on longer follow up have not been collected. REVIEWER'S CONCLUSIONS: The effects of volume expansion therapy have not been studied properly in patients with aneurysmal subarachnoid haemorrhage. At present, there is no sound evidence for or against the use of volume expansion therapy in patients with aneurysmal subarachnoid haemorrhage.

Humans↗
PubMed2000

Antifibrinolytic therapy for aneurysmal subarachnoid haemorrhage.

BACKGROUND: Re-bleeding is an important cause of death and disability in people with aneurysmal subarachnoid haemorrhage. This is probably due to dissolution of the clot by natural fibrinolytic activity. OBJECTIVES: The objective of this review was to assess the effect of antifibrinolytic treatment in patients with aneurysmal subarachnoid haemorrhage. SEARCH STRATEGY: We searched the Cochrane Stroke Group trials register and reference lists of articles. We also contacted drug companies. SELECTION CRITERIA: Randomised trials comparing oral or intravenous antifibrinolytic drugs (tranexamic acid, epsilon amino-caproic acid or an equivalent) with control in people with confirmed subarachnoid haemorrhage. DATA COLLECTION AND ANALYSIS: Two reviewers independently selected trials for inclusion and extracted the data. All five reviewers assessed trial quality. MAIN RESULTS: Eight trials involving 937 patients were included. Based on 579 patients in two trials, antifibrinolytic treatment did not show any benefit for poor outcome (death, vegetative state or severe disability) with an odds ratio of 1.05, 95% confidence interval 0.76 to 1.46. Death from all causes was not significantly influenced by treatment across all eight trials (odds ratio 0.96, 95% confidence interval 0.72 to 1.26). Antifibrinolytic treatment reduced the risk of re-bleeding reported at the end of follow-up, with some heterogeneity between the trials (odds ratio 0.59, 95% confidence interval 0.42 to 0.81). Treatment increased the risk of cerebral ischaemia in four trials (odds ratio 2.03, 95% confidence interval 1.40 to 2.94). Antifibrinolytic treatment showed no effect on the reported rate of hydrocephalus in four trials (odds ratio 1. 05, 95% confidence interval 0.71 to 1.56). REVIEWER'S CONCLUSIONS: Antifibrinolytic treatment does not appear to benefit people with aneurysmal subarachnoid haemorrhage. However, the trials were all done more than 10 years ago. New strategies may counteract the ischaemia-inducing potential of antifibrinolytic treatment and lead to improved outcome. A trial of combined antifibrinolytic and anti-ischaemia treatment is underway.

Antifibrinolytic Agents↗
PubMed2000

Treatment and outcome of severe intraventricular extension in patients with subarachnoid or intracerebral hemorrhage: a systematic review of the literature.

Severe intraventricular hemorrhage caused by extension from subarachnoid hemorrhage or intracerebral hemorrhage leads to hydrocephalus and often to poor outcome. We conducted a systematic review to compare conservative treatment, extraventricular drainage, and extraventricular drainage combined with fibrinolysis. We carried out a search in Medline of the literature between January 1966 and December 1998 and an additional hand-search from January 1990 to December 1998. Pharmaceutical companies were contacted to gather unpublished data. We reviewed the reference lists of all relevant articles. Two authors independently assessed eligibility of the studies and extracted data on characteristics of study design, patients, and treatment. Patients with primary intraventricular hemorrhage were excluded. Main outcome measures were death and poor outcome (defined as death or dependency) at the end of follow-up. No randomized clinical trial has yet been conducted so far, and we therefore reviewed only observational studies. The case fatality rate for conservative treatment (ten studies) was 78%. For extraventricular drainage (seven studies) it was 58% [relative risk versus conservative treatment (RR) 0.74; 95% confidence interval (CI) 0.55-0.99]. For extraventricular drainage with fibrinolytic agents (five studies) the case fatality rate was 6% (RR 0.08; 95% CI 0.02-0.24). The poor outcome rate for conservative treatment was 90%, that for extraventricular drainage 89% (RR 0.98; 95% CI 0.75-1.30) and that for extraventricular drainage with fibrinolytic agents 34% (RR 0.38; 95% CI 0.21-0.68). All RR values remained essentially the same after adjusting for age, sex, World Federation of Neurological Surgeons scale, study design, and year of publication for the studies that provided these data. Outcome is thus poor in patients with intraventricular extension of subarachnoid or intracerebral hemorrhage. This meta-analysis suggests that treatment with ventricular drainage combined with fibrinolytics may improve outcome for such patients, although this impression is derived only from an indirect comparison between observational studies. A randomized clinical trial is warranted.

Cerebral Hemorrhage↗
PubMed2000

Relapse prevention in major depressive disorder after successful ECT: a literature review and a naturalistic case series.

OBJECTIVE: Medication-resistance in major depressive disorder (MDD) may be related to high relapse rates after successful ECT when continued medication (C-MED) is used to prevent relapse. An alternative could be to continue ECT (C-ECT). METHOD: Patients with medication-resistant MDD responding to ECT were offered C-ECT without medication. Follow-up was 6 months. Publications from a literature search were screened against prespecified criteria. RESULTS: With C-ECT the 6-month relapse-rate was 50% (6/12, 95% CI:21-79) in our medication-resistant group. In the review we found with C-ECT 29% (7/24,CI:13-51) in 'unknown' medication resistance and no data about medication-resistant depression. With C-MED at 6 months: no data were found concerning medication-resistant depression, 28% (35/124,CI:20-36) in 'unknown' resistance and 13% (2/15,CI:2-41) in non-resistance. With C-MED at 12 months, 73% (16/22,CI:50-90), 50% (16/32,CI:32-68) and 27% (8/30,CI:12-46) were found, respectively. CONCLUSION: The efficacy of C-MED is related negatively to medication resistance before ECT. This may also be the case for C-ECT. Further studies with C-ECT are urgently needed.

Adult↗
PubMed2000

Risk factors for occlusion of infrainguinal bypass grafts.

OBJECTIVES: to identify risk factors for infrainguinal bypass occlusion and quantify the predictive value of data available before and after surgery. DESIGN: prospective study of 2650 patients who participated in a randomised trial of oral anticoagulants or aspirin after infrainguinal bypass surgery. MATERIALS AND METHODS: risk factors were determined by univariate Cox regression analysis, and entered in multivariate analyses which distinguished two models: analysis of factors available from history and clinical examination, completed by radiological and surgical data in the second model. To compare the information content of the two models, receiver-operator characteristic (ROC) curves were computed. RESULTS: in all patients female gender, critical ischaemia, femorocrural bypass grafting and non-venous graft material were independent risk factors. In patients with femoropopliteal bypasses female gender, critical ischaemia, poor run-off and non-venous graft material, the latter even in patients with supragenicular bypasses, were independent risk factors. The only significant risk factor in patients with femorocrural bypass grafts was use of a non-venous graft. The information contained in the first model was poor, whereas the second model had a higher predictive value. CONCLUSIONS: the major risk factor, even in above-knee bypasses, is non-venous graft material. The venous bypass graft should be offered to patients whenever possible.

Aged↗
PubMed2000

Outcome in patients with symptomatic occlusion of the internal carotid artery.

OBJECTIVES: to assess whether the risk of recurrent ischaemic stroke in patients with symptomatic internal carotid artery (ICA) occlusion has changed over the past decades, to determine risk factors for the occurrence of ischaemic stroke and to assess the risk of endarterectomy (CEA) of a severe contralateral ICA stenosis. DESIGN: retrospective cohort study. PATIENTS AND METHODS: patients with symptomatic ICA occlusion were identified from duplex registry files between 1991 and 1995. Information was obtained on vascular risk factors, performance of CEA for a contralateral ICA stenosis and on recurrence of ischaemic stroke. The rate of complications occurring within 30 days after CEA of the contralateral ICA in patients with symptomatic ICA occlusion was compared with the risk of CEA in patients with asymptomatic ICA occlusion and severe contralateral ICA stenosis (symptomatic or asymptomatic). RESULTS: ninety-seven patients were identified. Mean follow-up time was 26 months. The annual risk of (non-)fatal stroke was 5.3% for all strokes (95% CI 2. 9%-9.6%) and 3.8% for ipsilateral stroke (95% CI 1.9%-7.7%). Hyperlipidaemia and severe stenosis of the contralateral ICA were independent risk factors. Twenty-two of 32 patients with a severe stenosis of the contralateral ICA underwent CEA, of which one patient died and three suffered a minor ischaemic stroke. The perioperative risk of CEA in the control group of 20 patients with asymptomatic contralateral ICA occlusion was 0% (0 of 20). CONCLUSIONS: outcome in patients with symptomatic ICA occlusion has not substantially improved over the years. CEA for severe stenosis of the contralateral ICA carried a relatively high risk in our series, but deserves to be studied in a controlled design.

Adult↗
PubMed2000

The notion of "warning leaks" in subarachnoid haemorrhage: are such patients in fact admitted with a rebleed?

OBJECTIVE: Often patients with subarachnoid haemorrhage (SAH) recall a recent episode of acute severe headache, usually interpreted as a "warning headache" or first SAH. An alternative explanation is recall bias. The clinical and radiological features of patients with SAH were studied in relation to previous headaches or later rebleeding. METHODS: Patients with either a previous headache episode or a subsequent rebleed were selected from the SAH database in Utrecht within 1 month of the index SAH. The clinical condition was graded on the World Federation of Neurological Surgeons (WFNS) scale. The CT was reviewed and the amounts of subarachnoid blood, hydrocephalus, and intraventricular, intracerebral, and subdural blood were rated. Proportions were compared by unpaired or paired t test. RESULTS: Forty four of 390 patients (11%) had had a severe headache before their index SAH (11 of these had a subsequent rebleed); 31 other patients had a rebleed in hospital but no preceding headache. Patients with and without preceding headache did not differ in level of consciousness (14 of 44 v 11 of 31 were comatose), nor in any of the radiological features. After rebleeding (42 patients), 37 of 42 patients were comatose (v 11 of 42 before), and CT showed higher proportions of intracerebral haemorrhage (17%), intraventricular haemorrhage, (27%), and hydrocephalus (12%) than baseline scans. Intraventricular haemorrhage was twice as frequent after rebleeding than at baseline. CONCLUSIONS: The clinical and radiological features of patients admitted with SAH after a preceding bout of headache did not differ from those without such an episode, and are clearly dissimilar from those after documented rebleeds. The findings challenge the existence of minor "warning headaches".

Adult↗
PubMed2000

Magnetic resonance techniques for the identification of patients with symptomatic carotid artery occlusion at high risk of cerebral ischemic events.

BACKGROUND AND PURPOSE: We sought to assess whether MRI, MR angiography, or (1)H MR spectroscopy can be used to identify patients with symptomatic carotid artery occlusion (CAO) who are at high risk of recurrent ipsilateral cerebral ischemic events. METHODS: In 115 consecutive patients with transient or moderately disabling symptoms of cerebral or retinal ischemia and ipsilateral CAO, we studied the prognostic value of (1) presence of a border-zone infarct; (2) quantitative flow in the middle cerebral artery (MCA) ipsilateral to the CAO; and (3) metabolic ratios in the centrum semiovale ipsilateral to the CAO. RESULTS: Presence of a border-zone infarct and the rate of flow in the MCA did not have a significant relationship with recurrence of cerebral ischemic events. Patients with a low N:-acetyl aspartate (NAA)/choline ratio had an annual risk of recurrent, ipsilateral, cerebral ischemic events of 16.0% (95% CI, 9.5 to 27.0), whereas this risk was 4.2% (95% CI, 2.2 to 8.0) in those with a normal NAA/choline ratio (hazard ratio, 0. 43; 95% CI, 0.19 to 1.00). Patients who on entry had had only retinal symptoms had on average a higher NAA/choline ratio (mean difference, 0.25; 95% CI, 0.13 to 0.37) and a lower risk of recurrent cerebral ischemic events (odds ratio, 0.0; 95% CI, 0.0 to 0.6) than those with cerebral ischemic symptoms. CONCLUSIONS: NAA/choline ratio measured by (1)H MRS, but not the presence of a border-zone infarct or the amount of flow in the MCA, can identify patients with symptomatic CAO who are at risk of future ipsilateral cerebral ischemic events.

Adult↗
PubMed2000

Association of intraoperative transcranial doppler monitoring variables with stroke from carotid endarterectomy.

BACKGROUND AND PURPOSE: The outcomes of carotid endarterectomy (CEA) are, in addition to patient baseline characteristics, highly dependent on the safety of the surgical procedure. During the successive stages of the operation, transcranial Doppler (TCD) monitoring of the middle cerebral artery (MCA) was used to assess the association of cerebral microembolism and hemodynamic changes with stroke and stroke-related death. METHODS: By use of data pooled from 2 hospitals in the United States and the Netherlands, including 1058 patients who underwent CEA, the association of various TCD emboli and velocity variables with operative stroke and stroke-related death was evaluated by univariable and multivariable logistic regression analyses in combination with receiver operating characteristic (ROC) curve analyses. The impact of basic patient characteristics, such as age, sex, preoperative cerebral symptoms, and ipsilateral and contralateral internal carotid artery stenosis, on the prediction of operative stroke was also evaluated. RESULTS: We observed 31 patients with ischemic and 8 patients with hemorrhagic operative strokes. Four of these patients died. Emboli during dissection (odds ratio [OR] 1.5, 95% CI 0.8 to 2.9) and wound closure (OR 2.3, 95% CI 1.2 to 4.4) as well as > or =90% decrease of MCA peak systolic velocity at cross-clamping (OR 3.3, 95% CI 1.3 to 8.5) and > or =100% increase of the pulsatility index of the Doppler signal at clamp release (OR 7.1, 95% CI 1.4 to 35.7) were independently associated with stroke. The ROC area of this model was 0.69. Of the patient characteristics, only preoperative cerebral ischemia (OR 1.9, 95% CI 1.0 to 3.7) and > or =70% ipsilateral internal carotid artery stenosis (OR 0.5, 95% CI 0.2 to 0.9) were associated with stroke. Adding these patient characteristics to the model, the area under the ROC curve increased to 0.73. CONCLUSIONS: In CEA, TCD-detected microemboli during dissection and wound closure, > or =90% MCA velocity decrease at cross-clamping, and > or =100% pulsatility index increase at clamp release are associated with operative stroke. In combination with the presence of preoperative cerebral symptoms and > or =70% ipsilateral internal carotid artery stenosis, these 4 TCD monitoring variables reasonably discriminate between patients with and without operative stroke. This supports the use of TCD as a potential intraoperative monitoring modality to alter the surgical technique by enhancing a decrease of the risk of stroke during or immediately after the operation.

Aged↗
PubMed1999

[Creative mathematics with clopidogrel; exaggeration of the preventive effect by manufacturer].

A number of Dutch medical journals recently carried an advertisement stating that clopidogrel treatment reduced the number of ischaemic complications with 26%, compared with aspirin treatment. This is a miscalculation: the actual reduction is 0.51% in absolute rates, and 8.7% in relative terms. The error by Sanofi-Synthelabo arose by comparison of the event rates for clopidogrel (5.32%) as well as for aspirin (5.83%) with that in an imaginary placebo group (7.77%), yielding a reduction of ischaemic complications of 2.45% and 1.94% respectively; erroneous comparison of these two numbers leads to a difference of 26%.

Advertising↗
PubMed1999

Common carotid intima-media thickness and arterial stiffness: indicators of cardiovascular risk in high-risk patients. The SMART Study (Second Manifestations of ARTerial disease).

BACKGROUND: Common carotid intima-media thickness (IMT) and distensibility are markers of structural and functional vessel wall properties. Both parameters have been found in population-based studies to be associated with cardiovascular risk factors and prevalent cardiovascular disease. We investigated cross-sectionally whether IMT and distensibility are associated with cardiovascular risk in patients who already have vascular disease or atherosclerotic risk factors and evaluated the diagnostic ability of IMT and distensibility to discriminate between low- and high-risk patients. METHODS AND RESULTS: IMT and distensibility (change of diameter) of the left and right common carotid arteries were measured in the first 570 patients (537 for distensibility) enrolled in the Second Manifestations of ARTerial disease (SMART) study, a cohort study among patients with a manifestation of vascular disease or cardiovascular risk factors. Three risk scores were used to classify each patient's vascular risk. Areas under the curve (AUCs) of receiver-operating characteristic curves were calculated for IMT and distensibility after the patients were dichotomized on the median of the risk scores as the outcome. Risk scores increased nearly linearly with increasing IMT and decreasing distensibility. The AUCs for IMT predicting high-risk patients were 0.77, 0.73, and 0.77 based on the 3 risk scores. The AUCs for distensibility were 0. 65, 0.62, and 0.66. CONCLUSIONS: Common carotid IMT and distensibility are clear markers of cardiovascular risk in patients who already have vascular disease or atherosclerotic risk factors. IMT appears to discriminate between low- and high-risk patients better than distensibility.

Adult↗
PubMed1999

[Roaming through methodology. XV. Smoking grandfathers and other selection biases].

That some cigarette smokers live until 90 years of age does not allow conclusions about the life expectancy of smokers in general as, after all, the dead are invisible. In the same way, a case-control study of factor F (e.g. smoking) as a determinant of disease D (e.g. Alzheimer's disease) may be biased by excess mortality in subjects with the combination of disease D and factor F. The result is an underestimation of the combination F-D in survivors (survival bias). A different form of bias may occur in hospital-based observational studies, e.g. of patients with disease Y (brain infarction), with or without previous treatment with drug A (aspirin). If previous treatment is associated with relatively mild deficits, while only patients with severe deficits are admitted, the difference in stroke severity cannot be observed in hospital (referral bias). In comparison with a population-based follow-up study important groups of patients may, in either example, have been lost in the study.

Case-Control Studies↗