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Biomedical subjects

Uwe Siebert

Publications and source records attributed to Uwe Siebert.

49 records · Page 3Linked to original sources
PubMed2003

Cabergoline versus levodopa monotherapy: a decision analysis.

We evaluated the incremental cost-effectiveness of cabergoline compared with levodopa monotherapy in patients with early Parkinson's disease (PD) in the German healthcare system. The study design was based on cost-effectiveness analysis using a Markov model with a 10-year time horizon. Model input data was based on a clinical trial "Early Treatment of PD with Cabergoline" as well as on cost data of a German hospital/office-based PD network. Direct and indirect medical and nonmedical costs were included. Outcomes were costs, disease stage, cumulative complication incidence, and mortality. An annual discount rate of 5% was applied and the societal perspective was chosen. The target population included patients in Hoehn and Yahr Stages I to III. It was found that the occurrence of motor complications was significantly lower in patients on cabergoline monotherapy. For patients aged >/=60 years of age, cabergoline monotherapy was cost effective when considering costs per decreased UPDRS score. Each point decrease in the UPDRS (I-IV) resulted in costs of euro;1,031. Incremental costs per additional motor complication-free patient were euro;104,400 for patients <60 years of age and euro;57,900 for patients >/=60 years of age. In conclusion, this decision-analytic model calculation for PD was based almost entirely on clinical and observed data with a limited number of assumptions. Although costs were higher in patients on cabergoline, the corresponding cost-effectiveness ratio for cabergoline was at least as favourable as the ratios for many commonly accepted therapies.

Antiparkinson Agents↗
PubMed2003

Dopamine transporter imaging and SPECT in diagnostic work-up of Parkinson's disease: a decision-analytic approach.

As a diagnostic test for patients with suspected Parkinson's disease (PD), single photon emission computed tomography (SPECT) using [(123)I]FP-CIT tracer has better sensitivity but is more expensive than regular clinical examination (CE). Our objective was to evaluate the clinical and economic impacts of different diagnostic strategies involving [(123)I]FP-CIT SPECT. We developed a decision tree model to predict adequate treatment-month equivalents (ATME), costs, and incremental cost-effectiveness ratio (ICER) during a 12-month time horizon in patients with suspected PD referred to a specialized movement disorder outpatient clinic. In our cost- effectiveness analysis, we adopted the perspective of the German health care system and used data from a German prospective health care utilization study (n = 142) and published diagnostic studies. Compared strategies were CE only (EXAM+), SPECT only (SPECT+), SPECT following negative CE (SINGLE+), and SPECT following positive CE (DOUBLE+). Costs of SPECT amounted to euro;789 per investigation. Based on our model, expected costs (and ATME) were euro;946 (52.85 ATME) for EXAM+, euro;1352 (53.40 ATME) for DOUBLE+, euro;1731 (32.82 ATME) for SINGLE+, and euro;2003 (32.96 ATME) for SPECT+; performance of SPECT was induced in 0%, 54%, 56%, and 100% of the patients, respectively. DOUBLE+ was more effective and less expensive than SINGLE+ or SPECT+; thus these two do not offer reasonable choices. The ICER of DOUBLE+ compared to EXAM+ was euro;733 per ATME gained. In sensitivity analyses, the ICER of DOUBLE+ versus EXAM+ ranged from euro;63 to euro;2411 per ATME gained. Whether the diagnostic work-up of patients referred to a specialized movement disorder clinic with a high prevalence of PD should include [(123)I]FP-CIT SPECT depends on patient preferences and the decision maker's willingness to pay for adequate early treatment. SPECT should be used as a confirmatory test before treatment initiation and limited to patients with a positive test result in the clinical examination. These results should be adjusted to the specific setting and individual patient preferences.

Ambulatory Care Facilities↗
PubMed2003

High-resolution MR imaging of human atherosclerotic femoral arteries in vivo: validation with intravascular ultrasound.

PURPOSE: To establish a magnetic resonance (MR) imaging protocol for noninvasive in-vivo analysis of atherosclerotic femoral artery segments in humans and to compare the results to those of intravascular ultrasonography (IVUS). MATERIALS AND METHODS: In seven patients with peripheral arterial occlusive disease, 20 femoral arterial segments per person were examined by high-resolution (HR) MR imaging and IVUS. Comparison was possible in 123 of 140 segments. MR imaging was performed at 1.5 T with use of a three-dimensional (3D) time-of-flight sequence with an in-plane resolution of 0.78 x 0.49 mm(2). 3D contrast-enhanced MR angiography was used for exact positioning of the HR MR imaging slices. IVUS (3.5 F, 40 MHz) was performed with use of a motorized pullback system. Parameters analyzed included cross-sectional lumen area (LA), vessel area (VA), and extent of vessel wall calcification. RESULTS: Agreement between IVUS and HR MR imaging was analyzed with use of the Bland-Altman method. The paired LA measurements were in close agreement: the Bland-Altman mean bias in LA was -0.4 mm with a precision of +/-5.1 mm (P =.062). As a result of dorsal echo extinction in IVUS, VA measurements were feasible in only 74 of 140 segments. VA measurements were moderately correlated (r = 0.74; P <.0001), and a 25% overestimation by HR MR imaging compared to IVUS was observed. Intra- and interobserver comparisons for LA and VA measured with HR MR imaging did not show significant differences. Vessel wall calcifications were classified with a sensitivity of 91%, a specificity of 93%, and an accuracy of 93%. CONCLUSIONS: The MR imaging protocol introduced in the present study permits precise assessment of LA and extent of calcification in peripheral arterial occlusive disease in vivo. HR MR imaging shows high concordance with IVUS and may have the potential for noninvasive therapy monitoring.

Angiography, Digital Subtraction↗
PubMed2002

Coronary pressure measurement after stenting predicts adverse events at follow-up: a multicenter registry.

BACKGROUND: Coronary stenting is associated with a restenosis rate of 15% to 20% at 6-month follow-up, despite optimum angiographic stent implantation. In this multicenter registry, we investigated the relation between optimum physiological stent implantation as assessed by poststent fractional flow reserve (FFR) and outcome at 6 months. METHODS AND RESULTS: In 750 patients, coronary pressure measurement at maximum hyperemia was performed after angiographically apparently satisfactory stent implantation. Poststenting FFR was calculated and related to major adverse events (including need for repeat target vessel revascularization) at 6 months. In 76 patients (10.2%), at least 1 adverse event occurred. Five patients died, 19 experienced myocardial infarction, and 52 underwent at least 1 repeat target vessel revascularization. By multivariate analysis, FFR immediately after stenting was the most significant independent variable related to all types of events. In 36% of the patients, FFR normalized (>0.95), and event rate was 4.9% in that group. In 32% of the patients, poststent FFR was between 0.90 and 0.95, and event rate was 6.2%. In 32% of patients, poststent FFR was <0.90, and event rate was 20.3%. In 6% of the patients, FFR was <0.80, and event rate was 29.5% (P<0.001). CONCLUSIONS: FFR after stenting is a strong independent predictor of outcome at 6 months.

Blood Pressure↗
PubMed2002

The role of tacrolimus (FK506)-based immunosuppression on bone mineral density and bone turnover after cardiac transplantation: a prospective, longitudinal, randomized, double-blind trial with calcitriol.

BACKGROUND: Tacrolimus (FK506) is a new immunosuppressive drug in organ transplantation that has demonstrated experimentally to be more deleterious on bone mineral metabolism than cyclosporine. The purpose of this clinical study was to evaluate the effects of a tacrolimus-based immunosuppression on the skeleton and to investigate in a prospective, longitudinal, randomized, double-blind, study the effect of 0.25 microg calcitriol (1,25-dihydroxyvitamin D3) versus placebo in the prevention of bone loss and fracture rate after heart transplantion (HTx). METHODS: A total of 53 patients (5 female, 48 male, mean age: 53+/-11 years) were randomized to the study medication. Basic therapy included calcium and sex hormone replacement in hypogonadism. Bone mineral density of the lumbar spine (LS) and femoral neck (FN) were performed at baseline, after 12 and 24 months. Biochemical indexes of mineral metabolism were measured every 3 months. RESULTS: Overall bone mineral density (BMD) was significantly decreased after HTx (T-score-LS: 89+/-13%; FN: 88+/-14%). LS-BMD (% change in g/cm2) increased significantly within the study period in the calcitriol group (12 months: 7.1+/-8.1%, P<0.01; 24 months: 14.0+/-10.1%, P<0.01) and showed a positive trend in the placebo group (12 months: 4.5+/-9.3%, NS; 24 months: 6.2+/-8.0%, NS). FN-BMD in the calcitriol group was stable (12 months: -2.1+/-4.2%; NS; 24 months: -0.9+/-3.2%, NS). FN-BMD in the placebo group decreased significantly within the first 12 month follow-up period (-7.3+/-5.4; P<0.05) and stabilized within 2 years (-8.0+/-4.1%; P < 0.05). Fracture incidence was low during the study interval (first year: 5.0%, second year: 0%). Bone resorption markers decreased significantly during calcitriol therapy. CONCLUSIONS: High dose tacrolimus-based immunosuppressive regimen is associated with a rapid bone loss early after cardiac transplantation. Beyond the first 6 months after HTx, calcium, vitamin D, and hormone supplementation in hypogonadism lead sufficiently to bone mineral recovery. Besides immunosuppression, both concomitant hypogonadism and secondary hyperparathyroidism play a major role for the bone loss and should be therefore monitored and treated adequately. Low dose calcitriol should be substituted for at least 2 years as additional antiresorptive therapy.

Adult↗
PubMed2002

Safety of FFR-based treatment strategies: the Munich experience.

Fractional flow reserve (FFR) as a new technique for physiological assessment of coronary stenoses could identify patients with CAD in whom the deferral of an intended PCI was more beneficial than performing the planned procedure. It is up to now unknown whether a FFR-based therapy stratification is also safe in patients with multivessel disease and complex coronary lesions. This study demonstrates in 71 symptomatic patients with predominantly multivessel disease and angiographically intermediate coronary lesions that patients do not benefit from PCI procedures in terms of overall survival, target vessel patency or clinical symptoms during 12 month follow-up if FFR is above 0.75.

Aged↗
PubMed2002

Fractional flow reserve predicts major adverse cardiac events after coronary stent implantation.

OBJECTIVES: Determination of fractional flow reserve (FFR) allows the functional assessment of coronary stenoses before and after an intervention. Preliminary data suggest that a FFR > or = 0.94 is associated with an excellent clinical outcome after stent implantation. However, these results were limited both by the number of patients included and the use of non-contemporary stent designs. We sought to determine the prognostic value of FFR measurements in a large patient cohort undergoing coronary stent implantation. METHODS: Eighty-nine consecutive patients were enrolled in whom a stent implantation was performed and a pressure wire was used as a guide wire. Patients were followed for at least 6 months. Death, myocardial infarction (MI) and target vessel revascularization (TVR) were considered cardiac events. A FFR > or = 0.94 was regarded as an optimal functional result. RESULTS: A complete follow-up was available in all patents. Pre-interventional FFR increased from 0.66 +/- 0.16 to 0.95 +/- 0.05 (p < 0.0001) after stent implantation. Sixteen (18%) events occurred during follow-up including 10 (11.2%) TVR. Final FFR was significantly higher in patients without compared to patients with an event (0.92 +/- 0.06 vs. 0.96 +/- 0.05, p < 0.003). By univariate analysis, the presence of diabetes mellitus, left ventricular function, residual diameter stenosis and final FFR were associated with a worse clinical outcome. In the multivariate analysis, only the final FFR and left ventricular function remained as significant predictors for cardiac events (relative risk, 3.50; 95% CI: 1.29-9.52, P < 0.014, and 0.97; 95% CI: 0.93-1.00, p = 0.047). CONCLUSION: These results demonstrate in a nonselected patient cohort a strong correlation between FFR values after coronary stenting and subsequent cardiac events. Further studies have to investigate whether outcome after stenting might be improved by guiding the procedure with a pressure guide wire.

Aged↗
PubMed2002

The role of decision-analytic models in the prevention, diagnosis and treatment of coronary heart disease.

BACKGROUND: The rapidly expanding number and scope of health technologies used in the prevention, diagnosis, and treatment of coronary heart disease present physicians and policy makers with complex decisions that must be made even under uncertainty about the risks and benefits of these procedures. A physician must determine which procedures offer the best trade-off between potential harm and benefit, and yield the maximum expected health benefit for the patient. In addition, the cost-effectiveness of alternative choices must be considered to optimize resource allocations from a societal perspective, further complicating the decision making process. METHODS: Decision analysis is the application of explicit and quantitative methods to analyze decisions under conditions of uncertainty. Briefly, the basic concepts of decision analysis and cost-effectiveness analysis are described. Three examples of decision-analytic models for the prevention, diagnosis, and treatment of coronary heart disease are discussed to demonstrate situations in which decision analysis may be helpful, and to introduce different methodological approaches. CONCLUSION: Decision analysis may aid clinical decisions affecting individual patients as well as inform clinical policy decisions and decisions regarding national health policy. However, this method is not a complete procedure for determining resource allocation decisions in health care, because it cannot incorporate all the values relevant to such decisions.

Adult↗
PubMedDate not supplied

Resource utilization and costs of stroke unit care in Germany.

OBJECTIVES: Stroke imposes a considerable economic burden on the individual and society. Recently, the concept of an integrated stroke unit has been established in several countries to improve the outcome of patients. This study evaluates the costs of acute care of the different cerebrovascular insults in a stroke unit. METHODS: The study population included 340 patients who were consecutively admitted to the Department of Neurology, Philipps University Marburg, with the diagnosis of stroke or transient ischemic attack (TIA) between January 1 and June 30, 2000. Clinical status and course were evaluated by using the Barthel index and the modified Rankin scale. Employing a "bottom-up" approach, we calculated the costs from the perspective of the hospital and the third-party payer using data from provider departments and other published sources. RESULTS: Inpatient costs were 3020 euros (3290 US dollars) for TIA, 3480 euros (3790 US dollars) for ischemic stroke (IS), and 5080 euros (5540 US dollars) for intracerebral hemorrhage (ICH) and differed significantly among these subgroups (P < .05). Patient subgroups ranked in the same order for average length of stay at 9.4 days for TIA, 10.2 days for IS, and 11.9 days for ICH (P > .05). Approximately 30% of the hospital costs are due to physician charges and care. Imaging amounted to 10% and lab investigations to 14% of total costs, independent of the diagnosis. Postacute treatment, including inpatient rehabilitation, cost 9880 euros per patient. Across all diagnostic groups, a mean clinical improvement was observed at time of discharge. CONCLUSIONS: Care of patients with cerebrovascular events in a stroke unit causes a high demand of resources and has a considerable impact on health-care expenditure. Therefore, investigations comparing the stroke unit concept with other strategies in stroke care are necessary to evaluate the stroke unit concept for a rational use of available resources in patients with cerebrovascular events.

Aged↗
PubMedDate not supplied

Systematic assessment of decision models in Parkinson's disease.

OBJECTIVE: To give an insight into the structural and methodological approaches used in published decision-analytic models evaluating interventions in Parkinson's disease (PD) and to derive recommendations for future comprehensive PD decision models. METHODS: A systematic literature review was performed to identify studies that evaluated PD interventions using mathematical decision models. Using a standardized assessment form, information on the study design, methodological framework, and data sources was extracted from each publication and systematically reported. Strengths and limitations were assessed. RESULTS: We identified eight studies that used mathematical models to evaluate different pharmaceutical (n=7) and surgical (n=1) treatment options in PD. All models included economic evaluations. Modeling approaches comprised mathematical equations, decision trees, and Markov models with a time horizon ranging from 5 years to lifetime. All based progression on the evolution of clinical surrogate endpoints. Treatment effects were either modeled via reduction of symptomatic progression and/or initial symptomatic improvement or via reduction of adverse effect rates. No model is currently available that encompasses both the underlying biologic disease progression and the spectrum of all relevant complications and also links them to patient preferences and economic outcomes. CONCLUSIONS: Models have been successfully applied to evaluate PD treatments. However, currently available models have substantial limitations. We recommend that a comprehensive, generic, and flexible decision model for PD that can be applied to different treatment strategies should consider a large spectrum of clinically relevant outcomes and complications of the disease during a sufficiently long time horizon, include PD-specific mortality, systematically evaluate uncertainty including heterogeneity effects, and should be validated by independent data or other models. Approaches to model treatment effects included reduction of symptomatic progression, initial symptomatic improvement, or reduction of adverse effects. We believe that structural bias could be avoided if underlying disease progression and treatment effects on symptoms are modeled separately.

Cost-Benefit Analysis↗
PubMedDate not supplied

Cardiac CT in emergency department patients with acute chest pain.

Current strategies for the triage of patients who have chest pain but normal initial cardiac enzyme levels and nondiagnostic electrocardiograms do not permit efficient risk stratification. The potentially fatal consequences and high malpractice costs of missed acute coronary syndromes lead every year to the unnecessary hospital admission of about 2.8 million patients who present with acute chest pain in emergency departments in the United States. Most of these patients are at very low risk for an acute coronary syndrome. However, the standard clinical work-up does not provide information about the presence and extent of coronary artery disease. In most patients (80%-94%) with an acute coronary syndrome, a significant coronary artery stenosis can be detected with selective coronary angiography. High levels of diagnostic accuracy also have been established for the detection of significant coronary artery stenosis with the use of 16- and 64-section multidetector computed tomography (CT) in patients with stable angina. Preliminary data indicate that multidetector CT also can help quantify and characterize coronary atherosclerotic plaque and that the CT findings are in good agreement with those at intravascular ultrasonography. Although multidetector CT provides accurate information about the presence of coronary artery disease, large blinded observational studies are warranted to identify CT characteristics with high accuracy for diagnosis of acute coronary syndromes. Such information would enable the conduct of randomized controlled trials to determine whether the detection of coronary stenosis and plaque with multidetector CT improves triage and reduces the costs or increases the cost-effectiveness of management of acute chest pain.

Acute Disease↗