Influence Of Measurement Site Research Articles

Age and Sex Differences in Estimated Tibia Strength: Influence of Measurement Site

Variability in peripheral quantitative computed tomography (pQCT) measurement sites and outcome variables limit direct comparisons of results between studies. Furthermore, it is unclear what estimates of bone strength are most indicative of changes due to aging, disease, or interventions. The purpose of this study was to examine age and sex differences in estimates of tibia strength. An additional purpose of this study was to determine which tibia site or sites are most sensitive for detecting age and sex differences in tibia strength. Self-identifying Caucasian men (n=55) and women (n=59) aged 20–59yr had their tibias measured with pQCT from 5% to 85% of limb length in 10% increments distal to proximal. Bone strength index, strength strain index (SSI), moments of inertia (Ip, Imax, and Imin), and strength-to-mass ratios (polar moment of inertia to total bone mineral content [BMC] ratio [Ip:Tot.BMC] and strength strain index to total BMC ratio [SSI:Tot.BMC]) were quantified. There were significant (p<0.01) site effects for all strength variables and strength-to-mass ratios. Site×sex interaction effects were significant (p<0.05) for all strength variables. Men had greater (p<0.01) values than women for all strength variables. Sex differences in Ip, Imax, Ip:Tot.BMC, SSI, and SSI:Tot.BMC ratios were the smallest at the 15% site and peaked at various sites, depending on variable. Site×age interactions existed for Imax, Ip:Tot.BMC, and SSI:Tot.BMC. There were significant age effects, Imax, Ip:Tot.BMC, and SSI:Tot.BMC, as values were the lowest in the 20–29 age group. Age and sex differences varied by measurement site and variable, and larger sex differences existed for moments of inertia than SSI. Strength-to-mass ratios may reflect efficiency of the whole bone architecture.

Influence of Measurement Site on the Association between Visceral Adipose Tissue with Metabolic Risk

Influence of Measurement Site on the Association between Visceral Adipose Tissue with Metabolic Risk

Visceral and Subcutaneous Adiposity Measurements in Adults: Influence of Measurement Site

Excess abdominal adiposity is a known risk factor for cardiovascular diseases. Computed tomography can be used to examine the visceral (VAT) and subcutaneous (SAT) components of abdominal adiposity, but it is unresolved whether single-slice or multi-slice protocols are needed. Nine computed tomography scans were obtained in the lumbar spine region of 24 adults. The nine slices were obtained at three intervertebral positions (L2-L3, L3-L4, and L4-L5) and at 7 mm above and below these locations. Intra-site and inter-site differences in SAT, VAT, total adipose tissue, and the VAT/SAT ratio were examined using ANOVA and confidence intervals for pairwise differences between means. Intervertebral SAT values increased from 103.1 +/- 50.9 (standard deviation) cm(2) at L2-L3 to 153.3 +/- 68.8 cm(2) at L4-L5, whereas the corresponding VAT values decreased from 164.3 +/- 125.4 to 126.0 +/- 82.7 cm(2). The VAT/SAT ratio was not constant, decreasing from 1.8 +/- 1.4 to 0.9 +/- 0.7. Repeated-measures ANOVA indicated significant inter- and intra-site differences (p </= 0.02) for SAT, VAT, and the VAT/SAT ratio at L3-L4 and L4-L5 (p < 0.001). These differences show the limitation of using a single-slice assessment of abdominal fat distribution, both for a subject and between subjects. Furthermore, the sizeable differences in the intra-site scans indicate that precise repositioning is needed for longitudinal studies. In summary, our findings suggest that a multi-site imaging protocol may provide a more complete assessment of abdominal fat stores and distribution than use of a single site.

Evaluation of short-term precision for tibial ultrasonometry.

Tibial quantitative ultrasonometry is a relatively novel technique in the field of bone sonometry, an emerging alternative to bone densitometry. The implementation of this technique in a pediatric population could prove valuable from a clinical as well as a research viewpoint. In clinical practice it is necessary to know the precision of this technique and the possible influence on measurements before implementation. This study presents the precision in a Caucasian pediatric population and the influence of measurement site, dexterity, brand of coupling gel, and temperature of coupling gel. To assess intra- and interobserver variance duplicate measurements, with repositioning, ultrasonometry was performed in 10 children over a short period of time. The observers were blinded for the results of the other observer and after each measurement the skin markings were removed. Intraobserver variance for operator one (MHL) and for observer two (SFGR) was CV 0.43%. The interobserver variance was CV 0.61%. Left midtibial and right midtibial speed of sound (SOS) measurements showed no significant differences. There were, however, significant differences in both boys and girls between right proximal versus right midtibial, right midtibial versus right distal, and right proximal versus right distal (for all P < 0.001). One-way analysis of variance (ANOVA) showed that neither the use of different coupling gels nor an increase in gel temperature had a significant influence on measurements. The results of our study show that tibial quantitative ultrasonography (QUS) is a highly reproducible technique in a Caucasian pediatric population.