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Masaaki Uematsu - One of the best experts on this subject based on the ideXlab platform.
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long term results of direct and indirect endovascular revascularization based on the angiosome concept in patients with critical limb ischemia presenting with isolated below the knee lesions
Journal of Vascular Surgery, 2012Co-Authors: Osamu Iida, Yoshimitsu Soga, Keisuke Hirano, Daizo Kawasaki, Kenji Suzuki, Yusuke Miyashita, Hiroto Terashi, Masaaki UematsuAbstract:Objective We compared clinical outcomes between limbs with and without achievement of feeding artery flow by endovascular therapy (EVT) based on the angiosome concept in critical limb ischemia (CLI) patients with isolated below-the-knee (BTK) lesions and assessed factors influencing major amputation (MA). Method We analyzed 369 limbs from 329 consecutive patients (224 men; age, 70 ± 11 years) with ischemic ulceration or gangrene, or both, presenting with isolated BTK lesions (Rutherford class 5, 270 limbs; class 6, 99 limbs) with a pretreatment ankle-brachial index of 0.79 ± 0.26. Patients underwent successful EVT, without bypass surgery. Limbs were classified into direct (n = 200) and indirect (n = 169) groups by whether feeding artery flow to the site of ulceration or gangrene was successfully achieved, based on the angiosome concept. Unadjusted and adjusted (by propensity score matching) between-group rates of amputation-free survival (AFS) and freedom from major amputation (MA) and major adverse limb event (MALE) were compared by Kaplan-Meier analysis and the log-rank test. The independent determinants of MA in the direct and indirect groups were explored by multivariable analysis. Results During follow-up (mean, 18 ± 16 months), the overall limb salvage rate was 81% (300 of 369), death occurred in 36% (119 of 329), and the reintervention rate was 31% (114 of 369). After propensity score adjustment, the Estimated (± Standard Error) rates for AFS (49% ± 8% vs 29% ± 6%; P = .0002), freedom from MALE (51% ± 8% vs 28% ± 8%, P = .008), and major amputation (82% ± 5% vs 68% ± 5%, P = .01) were significantly higher in the direct group than in the indirect group for up to 4 years after the index procedure. After multivariable Cox proportional analysis, the independent factors associated with major amputation were hemoglobin A 1c level (hazard ratio [HR], 1.4; 95% confidential interval [CI], 1.1-1.9; P = .006) and cilostazol administration (HR, 0.28; 95% CI, 0.11-0.70; P = .006) in the direct group, and C-reactive protein level (HR, 1.2; 95% CI, 1.1-1.4; P = .002) in the indirect group. Conclusion Achieving direct flow by angioplasty based on the angiosome concept in CLI patients with isolated BTK lesions is clinically important for AFS and freedom from MA and MALE. Limb salvage factors appear to differ between patients with and without direct flow from the feeding artery after EVT.
Haruhiko Ogasawara - One of the best experts on this subject based on the ideXlab platform.
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Asymptotic Standard Errors of Estimated Standard Errors in structural equation modelling.
British Journal of Mathematical and Statistical Psychology, 2002Co-Authors: Haruhiko OgasawaraAbstract:Asymptotic Standard Errors of the Estimated asymptotic Standard Errors for parameter estimates in structural equation modelling are derived using the delta method with the assumption of multivariate normality for observed variables. The derivation covers the cases with and without restrictions on parameters. The result can be used to derive the asymptotic Standard Error of the z score (a parameter estimate divided by its Estimated Standard Error), which is frequently substantially different from one. The case of Standardized observed variables is dealt with as a typical example with restrictions on parameters. For actual covariance (correlation) structure models, the exploratory factor analysis model with factor rotation and the confirmatory factor analysis model are presented with numerical examples. Simulations are performed to assess the accuracy of our method for normally and non-normally distributed variables.
Anne Thiébaut - One of the best experts on this subject based on the ideXlab platform.
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Comparison of methods for estimating the attributable risk in the context of survival analysis
BMC Medical Research Methodology, 2016Co-Authors: Malamine Gassama, Jacques Bénichou, Laureen Dartois, Anne ThiébautAbstract:AbstractBackgroundThe attributable risk (AR) measures the proportion of disease cases that can be attributed to an exposure in the population. Several definitions and estimation methods have been proposed for survival data.MethodsUsing simulations, we compared four methods for estimating AR defined in terms of survival functions: two nonparametric methods based on Kaplan-Meier’s estimator, one semiparametric based on Cox’s model, and one parametric based on the piecewise constant hazards model, as well as one simpler method based on Estimated exposure prevalence at baseline and Cox’s model hazard ratio. We considered a fixed binary exposure with varying exposure probabilities and strengths of association, and generated event times from a proportional hazards model with constant or monotonic (decreasing or increasing) Weibull baseline hazard, as well as from a nonproportional hazards model. We simulated 1,000 independent samples of size 1,000 or 10,000. The methods were compared in terms of mean bias, mean Estimated Standard Error, empirical Standard deviation and 95% confidence interval coverage probability at four equally spaced time points.ResultsUnder proportional hazards, all five methods yielded unbiased results regardless of sample size. Nonparametric methods displayed greater variability than other approaches. All methods showed satisfactory coverage except for nonparametric methods at the end of follow-up for a sample size of 1,000 especially. With nonproportional hazards, nonparametric methods yielded similar results to those under proportional hazards, whereas semiparametric and parametric approaches that both relied on the proportional hazards assumption performed poorly. These methods were applied to estimate the AR of breast cancer due to menopausal hormone therapy in 38,359 women of the E3N cohort.ConclusionIn practice, our study suggests to use the semiparametric or parametric approaches to estimate AR as a function of time in cohort studies if the proportional hazards assumption appears appropriate.
Matthew Borgia - One of the best experts on this subject based on the ideXlab platform.
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reliability of outcome measures for people with lower limb amputations distinguishing true change from statistical Error
Physical Therapy, 2011Co-Authors: Linda Resnik, Matthew BorgiaAbstract:Background Use of outcome measures to examine outcomes of amputation is complicated by a number of factors, including ease of administration and lack of scientific evidence to guide selection and interpretation. Objective The purposes of this study were: (1) to estimate test-retest reliability of a modified version of the Prosthetic Evaluation Questionnaire (PEQ), scales of a version of the 36-Item Short-Form Health Survey questionnaire adapted for the veteran population (SF-36V), the Orthotics and Prosthetics Users' Survey (OPUS), the Patient-Specific Functional Scale (PSFS), the Two-Minute Walk Test, the Six-Minute Walk Test, the Timed “Up & Go” Test, and the Amputee Mobility Predictor; (2) to calculate minimal detectable change (MDC) of each measure; and (3) to conduct item analysis of the modified PEQ. Design This was a multi-site study with repeated measurements. Methods Forty-four patients with unilateral lower-limb amputation participated. Participants were tested twice within 1 week. We calculated test-retest reliability of each measure using intraclass correlation coefficient (ICC [2,1]), Estimated Standard Error of the measurement and MDC, and assessed scale score distribution. Results The study demonstrated strong test-retest reliability scores of performance measures (ICC=.83–.97) suggesting that these measures are good choices for evaluation of people with lower-limb amputation. Reliability of PEQ subscales (ICC=.41–.93) was comparable to that reported in the literature (ICC=.56–.90). Limitations This study examined only statistically measurable differences and did not evaluate whether changes in scores were clinically important. Conclusions Minimal detectable change scores can be used to determine whether change in test scores exceeds measurement Error associated with day-to-day variation. This is the first study to present test-retest reliability data on the self-reported OPUS scales, the PSFS in people with lower-limb amputations, and a new, easier-to-use scoring mechanism for the PEQ.
Osamu Iida - One of the best experts on this subject based on the ideXlab platform.
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long term results of direct and indirect endovascular revascularization based on the angiosome concept in patients with critical limb ischemia presenting with isolated below the knee lesions
Journal of Vascular Surgery, 2012Co-Authors: Osamu Iida, Yoshimitsu Soga, Keisuke Hirano, Daizo Kawasaki, Kenji Suzuki, Yusuke Miyashita, Hiroto Terashi, Masaaki UematsuAbstract:Objective We compared clinical outcomes between limbs with and without achievement of feeding artery flow by endovascular therapy (EVT) based on the angiosome concept in critical limb ischemia (CLI) patients with isolated below-the-knee (BTK) lesions and assessed factors influencing major amputation (MA). Method We analyzed 369 limbs from 329 consecutive patients (224 men; age, 70 ± 11 years) with ischemic ulceration or gangrene, or both, presenting with isolated BTK lesions (Rutherford class 5, 270 limbs; class 6, 99 limbs) with a pretreatment ankle-brachial index of 0.79 ± 0.26. Patients underwent successful EVT, without bypass surgery. Limbs were classified into direct (n = 200) and indirect (n = 169) groups by whether feeding artery flow to the site of ulceration or gangrene was successfully achieved, based on the angiosome concept. Unadjusted and adjusted (by propensity score matching) between-group rates of amputation-free survival (AFS) and freedom from major amputation (MA) and major adverse limb event (MALE) were compared by Kaplan-Meier analysis and the log-rank test. The independent determinants of MA in the direct and indirect groups were explored by multivariable analysis. Results During follow-up (mean, 18 ± 16 months), the overall limb salvage rate was 81% (300 of 369), death occurred in 36% (119 of 329), and the reintervention rate was 31% (114 of 369). After propensity score adjustment, the Estimated (± Standard Error) rates for AFS (49% ± 8% vs 29% ± 6%; P = .0002), freedom from MALE (51% ± 8% vs 28% ± 8%, P = .008), and major amputation (82% ± 5% vs 68% ± 5%, P = .01) were significantly higher in the direct group than in the indirect group for up to 4 years after the index procedure. After multivariable Cox proportional analysis, the independent factors associated with major amputation were hemoglobin A 1c level (hazard ratio [HR], 1.4; 95% confidential interval [CI], 1.1-1.9; P = .006) and cilostazol administration (HR, 0.28; 95% CI, 0.11-0.70; P = .006) in the direct group, and C-reactive protein level (HR, 1.2; 95% CI, 1.1-1.4; P = .002) in the indirect group. Conclusion Achieving direct flow by angioplasty based on the angiosome concept in CLI patients with isolated BTK lesions is clinically important for AFS and freedom from MA and MALE. Limb salvage factors appear to differ between patients with and without direct flow from the feeding artery after EVT.