137 research outputs found
Cost and patency rate targets for the development of endovascular devices to treat femoropopliteal arterial disease
PURPOSE: To determine the criteria that would make use of an endovascular
device cost-effective compared with bypass surgery and percutaneous
transluminal angioplasty in the treatment of femoropopliteal arterial
disease. MATERIALS AND METHODS: A decision model was developed to compare
treatment with the use of a hypothetical endovascular device with
established therapies. Cost-effectiveness from the perspective of the
health care system was considered. Outcome measures were lifetime costs
and quality-adjusted life-years. With the use of net health benefit
calculations and threshold analysis, combinations of costs and patency
rates were determined that would make the device cost-effective compared
with established therapies. In subgroup and sensitivity analyses, the
effect on decision-making of sex, age, indication, lesion type, procedural
risk, and society's willingness to pay for incremental gain in health were
explored. RESULTS: Use of a device that costs $3,000 would be
cost-effective compared with bypass surgery for critical ischemia if the
5-year patency rate is 29%-46%. Use of the same device would be
cost-effective compared with angioplasty for disabling claudication and
stenosis if the 5-year patency rate is 69%-86%. CONCLUSION: The target
combinations of costs and patency rates found in this study are probably
attainable, and further development of such endovascular devices seems
warranted
Study design for concurrent development, assessment, and implementation of new diagnostic imaging technology
With current constraints on health care resources and emphasis on value
for money, new diagnostic imaging technologies must be assessed and their
value demonstrated. The state of the art in the field of diagnostic
imaging technology assessment advocates a hierarchical step-by-step
approach. Although rigorous, such a hierarchical assessment is
time-consuming, and, given the current rapid advances in technology,
results are often too late to influence management and policy decisions.
The purpose of this article is to discuss a study design in which
development, assessment, and implementation of new diagnostic imaging
technology take place concurrently in one integrated process. An
empirically based pragmatic study design is proposed for imaging
technology assessment. To minimize bias and enable comparison with current
technology, a randomized controlled design is used whenever feasible and
ethical. Outcome measures should reflect the clinical decision-making
process based on imaging information and acceptance of the new test.
Outcome measures can include additional imaging studies requested, costs
of diagnostic work-up and treatment, physicians' confidence in therapeutic
decision making, recruitment rate, and patient outcome measures related to
the clinical problem. The key feature of the proposed study design is
analysis of trends in outcome measures over time
Peripheral arterial disease: gadolinium-enhanced MR angiography versus color-guided duplex US--a meta-analysis
PURPOSE: To summarize and compare the published data on
gadolinium-enhanced magnetic resonance (MR) angiography and color-guided
duplex ultrasonography (US) for the work-up for peripheral arterial
disease. MATERIALS AND METHODS: Studies published between January 1984 and
November 1998 were included if (a) gadolinium-enhanced MR angiography
and/or color-guided duplex US were performed for evaluation of arterial
stenoses and occlusions in the work-up for peripheral arterial disease of
the lower extremities, (b) conventional angiography was the reference
standard, and (c) absolute numbers of true-positive, false-negative,
true-negative, and false-positive results were available or derivable.
RESULTS: With a random effects model, pooled sensitivity for MR
angiography (97.5% [95% CI: 95.7%, 99.3%]) was higher than that for duplex
US (87.6% [95% CI: 84.4%, 90.8%]). Pooled specificities were similar:
96.2% (95% CI: 94.4%, 97.9%) for MR angiography and 94.7% (95% CI: 93.2%,
96.2%) for duplex US. Summary receiver operating characteristic analysis
demonstrated better discriminatory power for MR angiography than for
duplex US. Regression coefficients for MR angiography versus US were 1.67
(95% CI: -0.23, 3.56) with adjustment for covariates, 2.11 (95% CI: 0.12,
4.09) without such adjustment, and 1.73 (95% CI: 0.44, 3.02) with a random
effects model. CONCLUSION: Gadolinium-enhanced MR angiography has better
discriminatory power than does color-guided duplex US and is a highly
sensitive and specific method, as compared with conventional angiography,
for the work-up for peripheral arterial disease
Applications of decision analysis in diagnostic radiology
The subjects of this thesis are decision analysis and receiver operating characteristic (ROC)
methodology applied to radiological problems. This thesis is intended for those interested in
applying decision analytical techniques in diagnostic radiology, and in medicine in general.
Chapter II deals with the theory of decision trees and Markov processes. The basic concepts are
briefly explained and a few selected topics are discussed in more detaiL Chapter III describes
a decision model for the diagnostic workup and treatment of renovascular hypertension. Chapter
IV presents a Markov analysis of the decision whether, and when, to intervene in acute urinary
tract obstruction. Chapter V deals with the theory of receiver operating characteristic (ROC)
methodology. Basic concepts are explained and a number of selected issues are discussed in
detaiL Chapter VI presents an ROC analysis of the assessment of tumor extension in neoplastic
disease of the nose, paranasal sinuses, nasopharynx and parapharyngeal space, comparing
computer tomography (CT) and magnetic resonance imaging (MRI). Chapter VII presents the
results of an ROC analysis of orbital space-occupying lesions comparing the diagnosis made
by means of clinical evaluation, computer tomography (CT) and magnetic resonance imaging
(MRI). Chapter VIII presents the results of a study on fetal pulmonary maturity testing, involving
a number of interesting methodological issues of ROC analysis. A general discussion follows in chapter IX
Health-related quality of life after angioplasty and stent placement in patients with iliac artery occlusive disease: results of a randomized controlled clinical trial.
BACKGROUND: To assess the quality of life in patients with iliac artery
occlusive disease, we compared primary stent placement versus primary
angioplasty followed by selective stent placement in a multicenter
randomized controlled trial. METHODS AND RESULTS: Quality-of-life
assessments were completed by 254 patients in a telephone interview.
Assessment measures consisted of the RAND 36-Item Health Survey 1.0, time
tradeoff, standard gamble, rating scale, health utilities index, and
EuroQol-5D. The interviews were performed before treatment and after 1, 3,
12, and 24 months. When the 2 treatments were compared, no significant
difference was observed (P>0.05). All measurements showed a significant
improvement in the quality of life after treatment (P<0.05). The RAND
36-Item Health Survey measures physical functioning, role limitations
caused by physical problems, and bodily pain and the EuroQol-5D were the
most sensitive to the impact of revascularization. CONCLUSIONS:
Health-related quality of life improves equally after primary stent
placement and primary angioplasty with selective stent placement in the
treatment of intermittent claudication caused by iliac artery occlusive
disease
Balloon dilation and stent implantation for treatment of femoropopliteal arterial disease: meta-analysis
PURPOSE: To perform a meta-analysis of long-term results of balloon
dilation and stent implantation in the treatment of femoropopliteal
arterial disease. MATERIALS AND METHODS: The English-language literature
was searched for studies published between 1993 and 2000. Inclusion
criteria for articles were presentation of long-term primary patency
rates, standard errors (explicitly reported or derivable), and baseline
characteristics of the study population. Two reviewers independently
extracted data, and discrepancies were resolved by consensus. Primary
patency rates were combined by using a technique that allows adjustment
for differences across study populations. Analyses were adjusted for
lesion type and clinical indication. RESULTS: Nineteen studies met the
inclusion criteria, representing 923 balloon dilations and 473 stent
implantations. Combined 3-year patency rates after balloon dilation were
61% (standard error, 2.2%) for stenoses and claudication, 48% (standard
error, 3.3%) for occlusions and claudication, 43% (standard error, 4.1%)
for stenoses and critical ischemia, and 30% (standard error, 3.7%) for
occlusions and critical ischemia. The 3-year patency rates after stent
implantation were 63%-66% (standard error, 4.1%) and were independent of
clinical indication and lesion type. Funnel plots demonstrated an
asymmetric distribution of the data points associated with stent studies.
CONCLUSION: Balloon dilation and stent implantation for claudication and
stenosis yield similar long-term patency rates. For more severe
femoropopliteal disease, the results of stent implantation seem more
favorable. Publication bias could not be ruled out
Phase-referenced Interferometry and Narrow-angle Astrometry with SUSI
This thesis describes the development of an astrometric facility at the Sydney University Stellar Interferometer (SUSI) with an aim to measure at high precision the relative astrometry of bright close binary stars and ultimately to detect the presence of exoplanets within those binary star systems through observations of the systems’ perturbed motion. At the core of the facility is a new beam combiner that is phase-referenced to an existing primary beam combiner in the visible wave- length regime. The latter provides post-processed fringe-tracking information to the former for fringe stabilization and coherent integration of pre-recorded stellar fringes using newly developed data reduction software. Interference fringe packets of a binary star are recorded alternately; first the fringe packet of the primary, then the secondary, finally back to the primary again. The measurement of the fringe packet separation is facilitated by an air-filled differential delay line and a network of interferometer-based metrology systems. Characterizations and initial astronomical observations carried out with the dual beam combiner setup demonstrated for the first time the success of the dual-star phase-referencing technique in visible (~1μm) wavelengths. The current astrometric precision is larger than 100μas while the long term astrometric accuracy is yet to be characterized. In a parallel development, a complementary observing method using only the primary beam combiner is also demonstrated in this thesis. Relative astrometry of binary stars up to ~0.8” separation with this technique has been demonstrated to have precision of better than 100μas. A simple detection limit analysis based on a list of target binary stars estimates up to two exoplanet detections can be achieved with SUSI if the new astrometric facility attains precision of 10μas while the primary beam combiner operates at its designed peak performance. Finally, one new stellar companion was resolved and a preliminary astrometry for another suspected companion was estimated from the astronomical observation data collected throughout the course of this thesis
Comparative effectiveness of personalized lifestyle management strategies for cardiovascular disease risk reduction
Background-Evidence shows that healthy diet, exercise, smoking interventions, and stress reduction reduce cardiovascular disease risk. We aimed to compare the effectiveness of these lifestyle interventions for individual risk profiles and determine their rank order in reducing 10-year cardiovascular disease risk. Methods and Results-We computed risks using the American College of Cardiology/American Heart Association Pooled Cohort Equations for a variety of individual profiles. Using published literature on risk factor reductions through diverse lifestyle interventions-group therapy for stopping smoking, Mediterranean diet, aerobic exercise (walking), and yoga-we calculated the risk reduction through each of these interventions to determine the strategy associated with the maximum benefit for each profile. Sensitivity analyses were conducted to test the robustness of the results. In the base-case analysis, yoga was associated with the largest 10-year cardiovascular disease risk reductions (maximum absolute reduction 16.7% for the highest-risk individuals). Walking generally ranked second (max 11.4%), followed by Mediterranean diet (max 9.2%), and group therapy for smoking (max 1.6%). If the individual was a current smoker and successfully quit smoking (ie, achieved complete smoking cessation), then stopping smoking yielded the largest reduction. Probabilistic and 1-way sensitivity analysis confirmed the demonstrated trend. Conclusions-This study reports the comparative effectiveness of several forms of lifestyle modifications and found smoking cessation and yoga to be the most effective forms of cardiovascular disease prevention. Future research should focus on patient adherence to personalized therapies, cost-effectiveness of these strategies, and the potential for enhanced benefit when interventions are performed simultaneously rather than as single measures
Impact of guidelines for the management of minor head injury on the utilization and diagnostic yield of CT over two decades, using natural language processing in a large dataset
Objectives We investigated the impact of clinical guidelines for the management of minor head injury on utilization and
diagnostic yield of head CT over two decades.
Methods Retrospective before-after study using multiple electronic health record data sources. Natural language processing
algorithms were developed to rapidly extract indication, Glasgow Coma Scale, and CT outcome from clinical records, creating
two datasets: one based on all head injury CTs from 1997 to 2009 (n = 9109), for which diagnostic yield of intracranial traumatic
findings was calculated. The second dataset (2009–2014) used both CT reports and clinical notes from the emergency department, enabling selection of minor head injury patients (n = 4554) and calculation of both CT utilization and diagnostic yield.
Additionally, we tested for significant changes in utilization and yield after guideline implementation in 2011, using chi-square
statistics and logistic regression.
Results The yield was initially nearly 60%, but in a decreasing trend dropped below 20% when CT became routinely used for
head trauma. Between 2009 and 2014, of 4554 minor head injury patients overall, 85.4% underwent head CT. After guideline
implementation in 2011, CT utilization significantly increased from 81.6 to 87.6% (p = 7 × 10−7
), while yield significantly
decreased from 12.2 to 9.6% (p = 0.029).
Conclusions The number of CTs performed for head trauma gradually increased over two decades, while the yield decreased. In 2011,
despite implementation of a guideline aiming to improve selective use of CT in minor head injury, utilization significantly increased
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