DXA-Generated Z-Scores and T-Scores May Differ Substantially and Significantly in Young Adults

Central dual-energy X-ray absorptiometry (DXA) is the gold standard for non-invasive measurement of bone mineral density (BMD). Using this value and subject demographics, DXA software calculates T-scores and Z-scores. Professional society guidelines for the management of osteoporosis are based on T-scores and Z-scores, rather than on the actual BMD value. Although one expects T-scores and Z-scores to be very similar in young men and women for any given BMD measurement, little literature exists on this issue. Our clinical experience shows that some younger adult individuals (premenopausal women and men younger than 50 yr) have larger than expected difference between their DXA T-score and Z-score. This cross-sectional study evaluates the extent of this discordance between Z-scores and T-scores in a sample of 4275 men and women aged 20–49 yr. All subjects were scanned by central DXA using equipment manufactured by GE Lunar, GE, Madison, WI, or Hologic, Inc., Bedford, MA. Significant differences between Z-scores and T-scores were seen within individuals at the lumbar spine, total hip, femoral neck, and trochanter (p value < 0.001) for both DXA systems. Although these differences were less than half a standard deviation (SD) in most instances, the magnitude of difference was substantial at times, being 1 or more SD in up to 11% of cases (range: −1.95 to +1.54 SD). The smallest differences were seen at the total hip and the largest differences were seen at the femoral neck for both technologies. This is in part because there is no single standard Z-score definition, resulting in different methods of calculation across, and even within, DXA manufacturers. Standardization of Z-score definition and method of calculation is indicated. DXA Z-scores should be interpreted with caution in men and women aged 20–50 yr.     

正常幼儿语法发育的影响因素研究

【目的】了解影响幼儿语法发育的有关因素．为促进幼儿语言发育提供依据。【方法】采用现况定量研究方法。用多阶段分层不等比例抽样方法在北京4个城区抽取样本。用“中文早期语言与沟通发展量表”及个人背景问卷，对北京城区1056名16～30个月正常幼儿母亲或日间照顾人进行面对面问卷调查。运用Z评分法对幼儿语法粗分进行标准化．再用单因素和多重回归分析方法探讨影响幼儿语法发育的因素。【结果】凋查地区16～30个月龄正常幼儿平均语法表达结构得分由16个月时的6分增加到30个月时的84分，占总分的83％。单因素分析和多重回归分析结果显示，父亲受教育程度、父亲月收入、幼儿性格外向是幼儿语法发育的有利因素；幼儿开始说话月龄与幼儿语法发育得分Z评分呈负相关。【结论】家庭社会经济状况是影响小儿语法发育的重要因素。保健人员应重视幼儿语言发育，教育幼儿父母注意与儿童沟通．加强对儿童的早期教育，为儿童创造良好的早期语言环境。     

胎儿超声心动图检查定量11~17周正常胎儿主动脉和肺动脉内径Z-评分的初步研究

目的探讨早孕期（11^＋0周~13^＋6周）和中孕早期（14^＋0周~17^＋6周）胎儿主动脉内径（AO）与肺动脉内径（PA）与胎儿生物学生长参数的相关性,初步建立早孕期和中孕早期胎儿AO与PA的正常参考值范围及Z-评分方程,并评价方程的有效性。 方法随机选取孕周（GA）为（11^＋0周~17^＋6周）正常单胎胎儿270例,将成功显示左、右心室流出道切面的245例胎儿纳入研究,获得胎儿顶臀径（CRL）、双顶径（BPD）、股骨长径（FL）、孕周（GA）等生物学生长参数。在胎儿左、右心室流出道切面测量收缩末期AO及PA,以GA、BPD和FL作为独立自变量,AO及PA作为因变量,建立AO、PA的正常参考值范围,并对每个参数的绝对残差（SD）进行加权回归,建立Z-评分方程。 结果采用简单的线性回归模型,可以很好地描述AO和PA与非心脏生物特征参数（BPD、FL、GA）的关系。AO、PA与GA、BPD、FL均呈显著线性相关（GA与AO：r=0.9276,GA与PA：r=0.9271,BPD与AO：r=0.9551,BPD与PA：r=0.9558,FL与AO：r=0.9462,FL与PA：r=0.9483,均<0.001）,其中与BPD的相关性最强。 结论正常早孕期及中孕早期胎儿的AO、PA随着孕周的增加而增长,本研究初步建立了正常胎儿早孕期及中孕早期AO、PA的参考范围及其Z-评分方程。为早孕期及中孕早期评估胎儿大血管生长提供精确的参考标准,在早期筛查或诊断胎儿先天性心脏畸形方面具有潜在的应用价值。     

基于超声心动图测量的标准化肺动脉指数对法洛四联症根治术患者预后的预测价值

目的 应用超声心动图测量标准化肺动脉指数,探讨其在预测法洛四联症(TOF)根治术患者预后中的临床价值.方法 回顾性分析在我院行TOF根治术的465例患者资料,术前应用超声心动图测量并计算肺动脉瓣环Z值(PVAZ)、肺动脉主干Z值(MPAZ)及Nakata指数.绘制受试者工作特征(ROC)曲线预测TOF患者术中是否行跨瓣...     

保健食品中钙分析质量控制评价方法的研究

目的：研究保健食品功效成分检测实验室的钙分析质量控制的评价方法。方法：应用基于分析结果正态分布的z-值（z-score)质量控制评价方法对全国25个保健食品功能成分检测实验室的钙分析质量进行评价。结果：结果显示25个实验室中，有23个实验室的结果可以满足要求。结论：利用z-值质量控制评价方法直观、简便的特点，应用于分析质量控制中，可以取得较好的效果。     

The relationship between blood leptin level and bone density is specific to ethnicity and menopausal status

Leptin, the obesity hormone, has been linked to bone mineralization and tumorigenesis. In addition, both bone mineral density (BMD) and postmenopausal breast cancer are associated with obesity, but the interrelationships between obesity, leptin, BMD, and breast cancer are not yet clear. In particular, there is little published research comparing white and black women in terms of these variables. We obtained blood specimens for leptin analysis from a group of 320 breast cancer patients and controls with an ethnic composition of 49% white women and 51% black women. Distal and proximal radial BMD (DBMD and PBMD) were measured by dual-energy X-ray absorptiometry, and age- and ethnicity-specific standardized scores (Z-scores) were calculated for bone density. Blood leptin levels were determined by radioimmunoassay. Blood leptin level was not linked to breast cancer risk. Leptin levels were significantly higher in black women than in white women and were also significantly higher in obese and overweight women than in normal-weight women. Black women weighed more and had a higher body mass index (BMI) than white women. After controlling for BMI, leptin was correlated with DBMD ( r = .17; P < .05) and PBMD ( r = .21; P < .05) in whites, but not in blacks. Leptin was also correlated with both distal and proximal Z-scores in postmenopausal women ( r = .14 and .13; P < .05). Thus leptin may be a predictor for BMD in a population that is prone to have a low BMD, and this relationship is independent of the effect of body weight on leptin levels. Our results suggest that ethnicity and menopausal status should be considered when comparing results from different studies.     

Evaluation of brain perfusion SPECT using an easy Z-score imaging system (eZIS) as an adjunct to early-diagnosis of neurodegenerative diseases

The eZIS allows computer-assisted statistical analysis of brain perfusion SPECT images. We evaluated the diagnostic value of brain perfusion SPECT using eZIS in patients with various neurodegenerative diseases at a very early stage, within one year from onset.

Methods

SPECT using eZIS was performed for patients with Alzheimer disease (AD), dementia with Lewy bodies (DLB), frontotemporal dementia (FTD,), idiopathic Parkinson disease (PD) and vascular Parkinsonism (VP), multiple systemic atrophy of the cerebellar type (MSA-C), cortical cerebellar atrophy (CCA) and amyotrophic lateral sclerosis (ALS).

Results

Decreased rCBF was observed in the posterior cingulate cortex, precuneus and parietal cortex in AD; in the frontal gyrus and insula in FTD; in the occipital lobe, precuneus gyrus and posterior cingulate cortex in DLB; in the striatum and the thalamus in VP; in the cerebellum in CCA; in the cerebellum and pons in MSA-C and in the frontal cortex including the central sulcus in ALS. Increased rCBF in the striatum, thalamus and cerebellar dentate nuclei were observed in PD.

Conclusions

A specific rCBF pattern was observed for each disease using eZIS analysis, consistent with previous reports. Our results showed eZIS can be easily used as an adjunct to early-diagnosis of neurodegenerative diseases in any hospital.     

Z评分评价正常中晚孕期胎儿主动脉和肺动脉内径增长

目的 探讨Z评分对评价正常中晚孕期胎儿主动脉（AO）、肺动脉（PA）内径增长的应用价值。方法 通过前后2次产前超声心动图测量332胎正常胎儿的AO内径及PA内径。以AO内径、PA内径为应变量,胎儿双顶径（BPD）、胎儿股骨长径（FL）、孕周（GA）为自变量,建立回归方程,基于此计算AO、PA的Z评分。比较前后2次超声心动图检查Z评分的差异。结果 首次胎儿超声心动图检查时GA为（25.82±2.27）周（18~35周）,第2次检查时GA为（30.61±2.28）周（23~39周）。前后2次胎儿超声心动图检查所测胎儿AO内径、PA内径差异均有统计学意义（P均<0.05）。2次超声心动图检查的AO内径及PA内径均随GA、BPD及FL的增长而增长。同一孕妇胎儿AO及PA的Z评分随GA、BPD及FL的增长而相对稳定。前后2次产前超声心动图检查胎儿AO、PA的Z评分的差异均无统计学意义（P均>0.05）。结论 正常胎儿AO和PA内径的增长与生物学参数的增长呈正相关,但Z-评分在中晚孕期相对保持恒定。