The increase in bone mineral density by bisphosphonate with active vitamin D analog is associated with the serum calcium level within the reference interval in postmenopausal osteoporosis

Objectives: To examine the factors associated with increase in lumbar spine bone mineral density (LS-BMD) by bisphosphonates (BPs) with active vitamin D analog (aVD).

Methods: Two independent postmenopausal osteoporotic patients treated by BPs with aVD for 24 months (Study 1: n?=?93, Study 2: n?=?99) were retrospectively analyzed.

Results: In Study 1, LS-BMD of the patients significantly increased for 24 m (5.4%, p?r²: 0.088, p?=?.02). While average sCa of the patients was 9.2?mg/dL before treatment, it increased time-dependently to 9.6?mg/dL for 24 m by treatment. As each patient had their LS-BMD five times during the study, there were four instances of %LS-BMD in each patient, resulting in 372 instances of %LS-BMD in Study 1. The smallest Akaike’s information criterion value for the most appropriate cut-off levels of sCa for %LS-BMD by treatment every 6 m was 9.3?mg/dL. The %LS-BMD by treatment for 6 m during 24 m period in patients with sCa ≥9.3?mg/dL (1.5%) was significantly higher than that in patients with sCa <9.3?mg/dL (0.8%, p?=?.038). The results of Study 2 were similar to those of Study 1, confirming the phenomena observed.

Conclusion: sCa was associated with an increased LS-BMD by BPs with aVD.     

Research methods in performance validity testing studies: Criterion grouping approach impacts study outcomes

Objective: Performance validity test (PVT) research studies commonly utilize a known-groups design, but the criterion grouping approaches within the design vary greatly from one study to another. At the present time, it is unclear as to what degree different criterion grouping approaches might impact PVT classification accuracy statistics. Method: To analyze this, the authors used three different criterion grouping approaches to examine how classification accuracy statistics of a PVT (Word Choice Test; WCT) would differ. The three criterion grouping approaches included: (1) failure of 2+ PVTs versus failure of 0 PVTs, (2) failure of 2+ PVTs versus failure of 0–1 PVT, and (3) failure of a stand-alone PVT versus passing of a stand-alone PVT (Test of Memory Malingering). Results: When setting specificity at ≥.90, WCT cutoff scores ranged from 41 to 44 and associated sensitivity values ranged from .64 to .88, depending on the criterion grouping approach that was utilized. Conclusions: When using a stand-alone PVT to define criterion group status, classification accuracy rates of the WCT were higher than expected, likely due to strong correlations between the reference PVT and the WCT. This held true even when considering evidence that this grouping approach results in higher rates of criterion group misclassification. Conversely, when using criterion grouping approaches that utilized failure of 2+ PVTs, accuracy rates were more consistent with expectations. These findings demonstrate that criterion grouping approaches can impact PVT classification accuracy rates and resultant cutoff scores. Strengths, weaknesses, and practical implications of each of the criterion grouping approaches are discussed.     

Prediction of structural failure of tibial bone models under physiological loads: Effect of CT density–modulus relationships

Although finite element (FE) models can provide distinct benefits in understanding knee biomechanics, in particular the response of the knee to implants, their usefulness is limited by the modelling assumptions and input parameters. This study highlights the uncertainty of material input parameters derived from the literature and its limitation on the accuracy and usefulness of FE models of the tibia. An FE model of the intact human knee and a database of knee forces (muscles, ligaments and medial and lateral tibio-femoral contacts) were developed for walking and stair-descent activities. Ten models were constructed from ten different combinations of apparent bone density to elastic modulus material property relationships, published in the literature. Some of the published material property relationships led to predictions of bone strains in the proximal tibia which exceeded published failure criteria under loads imposed by normal activities. These relationships appear not to be applicable for the human tibia. There is a large discrepancy in proposed relationships that cover the cancellous bone density range. For FE models of the human tibia, the material relationship proposed by Morgan et al., which assumed species and anatomic site dependence, produced the most believable results for cancellous bone. In addition to casting doubt on the use of some of the published density–modulus relationships for analysis of the human proximal tibia, this study highlights the need for further experimental work to characterise the behaviour of bone with intermediate densities.     

高海拔地区急性呼吸窘迫综合征和多器官功能障碍综合征诊断标准的研究--附高海拔地区急性呼吸窘迫综合征诊断标准重修意见稿

目的：判别高海拔地区急性呼吸窘迫综合征（H－ARDS）和多脏器功能障碍综合征（H－MODS）诊断指标参数和平原的差异，重估原H－ARDS诊断标准（1999年兰州会议）的实用性和可操作性。方法：将资料齐全且符合庐山、Marshall ARDS/MODS诊断标准的360例患者，根据所在海拔高度分为平原对照组（CG，n=93),≥1517m高度组（H1G，n=223),2261-2400m高度组（H2G，n=44)。3组均按庐山、Marshall和自拟ARDS／MODS的标准（简称兰州标准）建成3个标准数据模型，绘制ROC曲线。根据曲线下面积、最佳截断点对比3个标准在不同海拔梯度上预测ARDS／MODS结局的准确性。结果：用庐山标准验证CG组ROC下面积、敏感度、特异度优于Marshall标准，两者相比ROC下面积、敏感度、特异度依次为0．823、0．833、0．731比0．815、0．767、0．763；但用于验证高海拔区如H2G则庐山标准明显低于兰州标准，两标准的ROC下面积、敏感度、特异度依次为0．855、0．583、0．969比0．914、1．000、0．657；氧合指数（PaO2/FiO2)的最佳界值在CG、H1G和H2G依次为198．32mmHg、131.50mmHg、97.58mmHg；3组ARDS／MODS按平原标准评分分级，CG比较均匀分布在1－3级，而H1G和H2G的病例多集中在3级，多构成比χ^2检验，P＜0．000。结论：（1）高海拔地区ARDS诊断标准与平原地区有明显差异，海拔高度≥1517m的兰州地区可能在区分平原与高原ARDS诊断标准是上一个有意义的分界线。已建立的H－ARDS诊断标准参数符合本地区实际，基本可行，参数范围仍宽，建议适度修改。MODS各项指标虽与平原有不同的变化趋向，但样本量较少，标准有待进一步完善。     

移植肾肾动脉狭窄的彩色多普勒超声诊断

目的 探讨运用多项彩色多普勒超声（CDUS）指标综合诊断移植肾肾动脉狭窄（TRAS）的的新标准。方法 回顾性分析20例经数字减影血管造影（DSA）证实的TRAS的CDUS指标：移植肾肾动脉收缩期峰值血流速度（PSV）、肾动脉与髂外动脉PSV比值（RIR）、肾动脉与叶间动脉PSV比值（峰值流速后比）和叶间动脉阻力指数（RI）；并与对照组相应指标对比。结果 TRAS组与对照组的上述4项指标之间均存在显著统计学差异（P〈0．001）。新标准具有良好的敏感性（100％）和较高的特异性。结论 新标准能够提高CDUS对TRAS的诊断率。     

Food or nutrient pattern assessment using the principal component analysis applied to food questionnaires. Pitfalls,tips and tricks

We considered the Blom’s transformation, a statistical method aimed to normalise and standardise food intakes before principal component analysis. A simulation study was performed to evaluate the eigenvalue distribution of a correlation matrix under common conditions in food questionnaire analysis. The scree plot visual inspection and the Guttman–Kaiser (GK) criterion were compared to Horn’s parallel analysis to evaluate their efficacy in food pattern identification. The scree plot results as a monotone continuous series when no food patterns are present. In this situation, about 50% of the eigenvalues assume a value higher than one, showing a first fallacy of the GK. When three food patterns are simulated a clear discontinuity appears after the third eigenvalue, showing that the scree-plot visual inspection is a suitable method to identify food patterns. Finally, according to the present work it appears that the GK generates a number of false-positive food patterns.     

State selection in Markov models for panel data with application to psoriatic arthritis

Markov multistate models in continuous‐time are commonly used to understand the progression over time of disease or the effect of treatments and covariates on patient outcomes. The states in multistate models are related to categorisations of the disease status, but there is often uncertainty about the number of categories to use and how to define them. Many categorisations, and therefore multistate models with different states, may be possible. Different multistate models can show differences in the effects of covariates or in the time to events, such as death, hospitalisation, or disease progression. Furthermore, different categorisations contain different quantities of information, so that the corresponding likelihoods are on different scales, and standard, likelihood‐based model comparison is not applicable. We adapt a recently developed modification of Akaike's criterion, and a cross‐validatory criterion, to compare the predictive ability of multistate models on the information which they share. All the models we consider are fitted to data consisting of observations of the process at arbitrary times, often called ‘panel’ data. We develop an implementation of these criteria through Hidden Markov models and apply them to the comparison of multistate models for the Health Assessment Questionnaire score in psoriatic arthritis. This procedure is straightforward to implement in the R package ‘msm’. Copyright © 2015 John Wiley & Sons, Ltd.