Short term in vivo precision of whole body composition measurements on the Horizon A densitometer.

INTRODUCTION: Dual-energy X-ray absorptiometry (DXA) is increasingly being used to assess abnormalities in body composition associated with a wide variety of conditions including obesity, sarcopenia, diabetes, anorexia, human immunodeficiency virus lipodystrophy, malabsorption and neuromuscular disorders. The objective of this study was to determine the short-term in vivo precision and least significant change in serial body composition measurements provided by the Hologic Horizon A densitometer as there is no published, peer reviewed body composition precision data on Horizon scanners in the medical literature. METHODS: After acquiring two new Hologic Horizon A densitometers, short term precision scanning was performed on the two scanners using different groups of 30 volunteers, who had duplicate scans with all scans performed by the same operator. Using the International Society of Clinical Densitometry's advanced precision tool, the scan data were recorded and the coefficient of variation (CV) and least significant change (LSC) determined for total fat, lean and bone mineral content (BMC) and bone mineral density (BMD). RESULTS: Coefficients of variation of 0.78% and 0.77% were achieved for total fat (LSC at 95% confidence 2.15%) and 0.52% and 0.40% for total lean (LSC at 95% confidence 1.45% and 1.11%). CONCLUSIONS: These results indicate that the two Horizon A scanners in this study exceeded the minimum acceptable precision values by roughly a factor of four and are therefore capable of detecting small differences in lean and fat mass of 1-2% between two measurements at 95% confidence.

Impact of androgen suppression and zoledronic acid on bone mineral density and fractures in the Trans-Tasman Radiation Oncology Group (TROG) 03.04 Randomised Androgen Deprivation and Radiotherapy (RADAR) randomized controlled trial for locally advanced prostate cancer.

OBJECTIVE: To study the influence of adjuvant androgen suppression and bisphosphonates on incident vertebral and non-spinal fracture rates and bone mineral density (BMD) in men with locally advanced prostate cancer. PATIENTS AND METHODS: Between 2003 and 2007, 1071 men with locally advanced prostate cancer were randomly allocated, using a 2 × 2 trial design, to 6 months i.m. leuprorelin (androgen suppression [AS]) before radiotherapy alone ± 12 months additional leuprorelin ± 18 months zoledronic acid (ZdA), commencing at randomization. The main endpoint was incident thoraco-lumbar vertebral fractures, which were assessed radiographically at randomization and at 3 years, then reassessed by centralized review. Subsidiary endpoints included incident non-spinal fractures, which were documented throughout follow-up, and BMD, which was measured in 222 subjects at baseline, 2 years and 4 years. RESULTS: Incident vertebral fractures at 3 years were observed in 132 subjects. Their occurrence was not increased by 18 months' AS, nor reduced by ZdA. Incident non-spinal fractures occurred in 72 subjects and were significantly related to AS duration but not to ZdA. Osteopenia and osteoporosis prevalence rates at baseline were 23.4 and 1.4%, respectively, at the hip. Treatment for 6 and 18 months with AS caused significant reductions in hip BMD at 2 and 4 years (P < 0.01) and ZdA prevented these losses at both time points. CONCLUSION: In an AS-naïve population, 18 months of ZdA treatment prevented the sustained BMD losses caused by 18 months of AS treatment; however, the study power was insufficient to show that AS duration or ZdA influenced vertebral fracture rates.

Utility of lung density measurements in the diagnosis of emphysema.

BACKGROUND: The role of computerised tomography (CT) lung density measurements in objective quantification of emphysema is uncertain. The aim of this study was to determine normal reference values for CT lung density measurements and investigate their utility in identifying subjects with clinical emphysema. METHODS: Normal subjects (non-smokers, no respiratory disease, n=185) and subjects with clinical emphysema (post-bronchodilator FEV(1)/FVC <70%, > or =10 pack years tobacco smoking, no childhood asthma and, either D(LCO)/VA <80% predicted and/or macroscopic emphysema on CT, n=22) were identified from a random population survey. Subjects underwent CT scanning, with measurement of areas of low attenuation as a percentage of total area (RA%) for three standardised slices and two reconstruction algorithms with a density threshold of -950 HU. Reference values in normal subjects, and ability of the measurements to discriminate between the two groups were determined. RESULTS: Reference values for individual subjects showed wide confidence intervals (standard resolution scans, RA% females 0.2-3.9%, males 0.4-8.7%.) Subjects with emphysema had greater RA% values compared with normal subjects, the difference being most marked in apical slices (standard resolution algorithm, apical slice, median RA% 2.9% (95% CI 0.4-11.1%) vs. 0.1% (95% CI 0.0-0.5%), emphysema vs. normal subjects, respectively). Logistic regression analysis showed poor discriminant ability to distinguish between the groups, the most favourable cut-off yielding a sensitivity and specificity of 83.3% and 62.8%, respectively. CONCLUSIONS: CT lung density measurements cannot reliably detect the presence of emphysema in an individual. We recommend further investigation into lung density measurements before their widespread use in clinical practice.

The use of antithrombotics in patients presenting with stroke and atrial fibrillation.

Antithrombotics have been shown to decrease the risk of stroke in patients with atrial fibrillation (AF). However they are associated with an increased risk of bleeding. We assessed the frequency and appropriateness of antithrombotic therapy in patients admitted to our service with stroke and AF. A retrospective case study of 219 patients (mean age 77.2 years) admitted between January 1999 and 31 December 2001 with a diagnosis of stroke and AF was done. Patient characteristics, presence of comorbid conditions, knowledge of preadmission AF, medication history and appropriateness of antithrombotic treatment were recorded. One hundred and fifty patients were known to have had AF prior to admission. Forty-one presented with an intracranial hemorrhage (19 on warfarin, 10 on aspirin). Of those patients with known AF only 43 were on treatment consistent with the guidelines. Warfarin was recommended in 144 of the whole cohort, but only 39 were taking it. Fifty-three patients were receiving aspirin although warfarin was the recommended treatment. Fifty-four with known AF were not on any antithrombotic treatment. Factors significantly associated with the use of antithrombotic treatment were history of AF (p = 0.0004), valvular heart disease (p = 0.02), venous thromboembolism (p = 0.04), risk of thromboembolism (p = 0.003) and presentation with a nonischemic infarct (p = 0.008). Antithrombotic therapy use in our patients differs significantly from guideline recommendations.

Physiological associations of computerized tomography lung density: a factor analysis.

BACKGROUND: Objective quantification of emphysema using computerized tomography (CT) density measurements is rapidly gaining wide acceptance as an in vivo measurement tool. However, some studies have suggested that abnormal lung function in the absence of emphysema can affect lung density, and the role of such measurements in identifying and monitoring the progression of emphysema is not clear. OBJECTIVE: To clarify the relationship between lung density measurements and pulmonary function. METHODS: CT measurements of the proportion of lung occupied by low density tissue (as percentage of lung area below predetermined Hounsfield unit [HU] thresholds) were obtained in a large random population (n = 739) and the association with detailed pulmonary function tests studied using factor analysis. RESULTS: Density measurements showed a greater association with measures of hyperinflation and airflow obstruction than measures of gas transfer (correlation coefficient, high resolution scan, -950HU threshold vs FEV1/FVC, RV, and DLCO/VA of -0.39, 0.22, and -0.15 respectively). The strongest lung density factor coefficients of 0.51 (standard resolution scan, - 950 HU threshold) and 0.46 (high resolution scan, - 910 HU threshold) were seen with factors predominantly consisting of measures of airflow obstruction and hyperinflation. Most variation in lung density was not accounted for by lung function measurements (communality 0.21-0.34). CONCLUSION: Lung density measurements associate most strongly with measures of airway disease that are not specific to emphysema.

A magnetic resonance imaging analysis of the infraclavicular region: can brachial plexus depth be estimated before needle insertion?

In this study we examined the anatomy of the infraclavicular region to assess the possibility of estimating brachial plexus depth before performing an infraclavicular block, by using readily identifiable landmarks such as the coracoid process (CP) and the clavicle (CL). Four parasagittal planes across the infraclavicular region were analyzed in 21 individual series of magnetic resonance imaging studies. Measurements included distance to the plexus from the skin of the anterior chest wall, position of the plexus relative to the CL, and clavicular width. The brachial plexus is located directly below the CL in the parasagittal plane 1 cm medial to the CP. If one inserts a needle in this same plane at a point in line with the inferomedial edge of the CP, then plexus depth can be estimated as follows. If the needle is raised, as a whole, straight up from the planned point of insertion to be level with the top of the CL, then the distance from the tip of the needle to a point midway across the width of the CL is equivalent to the distance from the insertion point to the plexus. Furthermore, not only is it uncommon to find the lung in this same parasagittal plane, but when it does appear, it is well behind the plexus. Estimating plexus depth, or "depth gauging," in the infraclavicular region is achievable and is a potentially useful strategy. Further study is required to confirm this finding in the clinical environment.