Does a Novice Technician Produce Results Similar to That of an Experienced DXA Technician When Assessing Body Composition and Bone Mineral Density?

Dual energy X-ray absorptiometry is a commonly used clinical assessment tool for body composition and bone mineral density, which is gaining popularity in athletic cohorts. Results from body composition scans are useful for athletic populations to track training and nutritional interventions, whilst bone mineral density scans are valuable for athletes at risk of developing stress fractures due to low bone mineral density. However, no research has ascertained if a novice technician (accredited but not experienced) could produce similar results to an experienced technician. Two groups of recreational athletes were scanned, one by an experienced technician, one by a novice technician. All participants were scanned twice with repositioning between scans. The experienced technician\u27s reliability (ICC 0.989 - 0.998, percentage change in mean -0.01 - 0.10), precision (typical error as CV% 0.01 to 0.47. standard error of measurement percentage 0.61% - 1.39%) and sensitivity to change (smallest real difference percentage 1.70% - 3.85%) were similar, however superior, to those of the novice technician. The novice technician results were: reliability (ICC 0.985 - 0.997, percentage change in mean -0.03 - 0.23), precision (typical error as CV% 0.03 - 0.75%, standard error of measurement percentage 1.06% - 2.12%) and sensitivity to change (smallest real difference percentage 2.73% - 5.86%). Extensive experience whilst valuable is not a necessary requirement to produce quality results when undertaking whole body dual energy X-ray absorptiometry scanning

Combination of acoustic trapping and impedance spectroscopy for platelet analysis

A combination of acoustic trapping and impedance spectroscopy for micrometer-sized objects is here presented for the first time. Acoustic trapping has proven to be a well-functioning method for non-contact immobilization and positioning of particles or cells in microfluidic channels. The combination with impedance spectroscopy allows for simultaneous electrical measurements on the trapped objects. Silica (8 μm) and polystyrene particles (3, 7, 10, and 12 μm) in saline solution, as well as human platelets in TAB buffer, have been trapped and measured. Both the saline and buffer solution had a base impedance magnitude of ̴ 500 Ω at the utilized frequency range (100 kHz–5 MHz). The impedance magnitude for the trapped particles was ̴ 30 Ω higher than the base impedance magnitude for the saline solution at 100 kHz–15 MHz. For the platelets, the impedance magnitude was ̴ 60 Ω higher compared to the buffer at 100 kHz. Furthermore, the setup can be used for studies on the reaction of a trapped cluster of objects, for example cells, when the environment is changed. One way of changing the environment would be to introduce drugs in different concentrations into the channel. However, the electrical characteristics of the fluid cannot be changed. An application is presented where the system is used for measurements on platelet activation. Platelets were activated by 20 μM TRAP while trapped, which yielded a reversible impedance magnitude decrease of ̴̴ 15 Ω at 100 kHz. 40 μM TRAP resulted in an initial decrease of ̴ 24 Ω and a sustained decrease of ̴ 15 Ω at 100 kHz. The setup presented shows great potential for being developed to an analysis system for micrometer-sized objects, for example for characterization of platelet activation

Reliability and Precision of the Nana Protocol to Assess Body Composition Using Dual Energy X-ray Absorptiometry

The Nana positioning protocol is widely used to position participants to minimize technical error when undertaking body composition scanning and analysis with a Dual energy X-Ray absorptiometry (DXA) machine. Once biological and technical errors are accounted for, the only variation in test–retest results is from statistical fluctuation or machine error. Therefore, the aim of this study is to assess the test–retest reliability of the Nana positioning protocol and establish the smallest real difference percentage (SRD%). A gender-balanced group of 30 participants (15 males, 15 females) underwent two scans in succession using the Nana positioning protocol, with repositioning between scans. Percentage change in mean with typical error, Intraclass Correlation Coefficients (ICC), and standard error measurement percentage (SEM%) were used to identify the test–retest reliability and error rate of these protocols. Additionally, SRD% was calculated to assess the point at which clinically important changes occurred in a participant. The reliabilities of the whole body and regional scans were excellent. Percentage change in mean ranged between 0.00% and 0.23%. High reproducibility of the Nana positioning protocol was evident through an ICC ranging between 0.966–1.000. Additionally, typical error, SEM%, and SRD% were all low. Interestingly, fat mass was associated with the largest fluctuations observed to be associated with any of the parameters assessed. When all sources of biological and technical errors have been accounted for, the Nana positioning protocol has excellent test–retest reliability and produces low SEM% and SRD%

Dual energy X-ray absorptiometry positioning protocols in assessing body composition: A systematic review of the literature:A systematic review of the literature

OBJECTIVES: To systematically identify and assess methods and protocols used to reduce technical and biological errors in published studies that have investigated reliability of dual energy X-ray absorptiometry (DXA) for assessing body composition. DESIGN: Systematic review. METHODS: Systematic searches of five databases were used to identify studies of DXA reliability. Two independent reviewers used a modified critical appraisal tool to assess their methodological quality. Data was extracted and synthesised using a level of evidence approach. Further analysis was then undertaken of methods used to decrease DXA errors (technical and biological) and so enhance DXA reliability. RESULTS: Twelve studies met eligibility criteria. Four of the articles were deemed high quality. Quality articles considered biological and technical errors when preparing participants for DXA scanning. The Nana positioning protocol was assessed to have a strong level of evidence. The studies providing this evidence indicated very high test–retest reliability (ICC 0.90–1.00 or less than 1% change in mean) of the Nana positioning protocol. The National Health and Nutrition Examination Survey (NHANES) positioning protocol was deemed to have a moderate level of evidence due to lack of high quality studies. However, the available studies found the NHANES positioning protocol had very high test–retest reliability. Evidence is limited and reported reliability has varied in papers where no specific positioning protocol was used or reported. CONCLUSIONS: Due to the strong level of evidence of excellent test–retest reliability that supports use of the Nana positioning protocol, it is recommended as the first choice for clinicians when using DXA to assess body composition

Loss of size-selectivity at histamine-induced exudation of plasma proteins in atopic nasal airways.

Plasma proteins occur in the airway lumen in inflammatory airway diseases. This study tests the hypothesis that airway microvascular-epithelial exudation of plasma proteins, as induced by a non-injurious inflammatory mediator, is characterized by loss of size-selectivity. Using a nasal pool-device, the nasal mucosa of 10 allergic individuals, without current disease, was sequentially exposed to saline and histamine (40 and 400 microg ml(-1)). Nasal lavage fluid and blood-levels of albumin (69 kD) and alpha2-macroglobulin (720 kD) were determined. Histamine produced concentration-dependent exudation of albumin and alpha2-macroglobulin. The albumin/alpha2-macroglobulin concentration ratio of the saline lavage fluid (baseline) was 40+/-19. However, at the histamine challenges the ratios were 25+/-3 and 22+/-2, respectively, which did not differ from that of circulating plasma (22+/-2). We conclude that there is minor and size-selective luminal entry of plasma proteins at baseline. However, at concentration-dependent exudative responses to histamine, plasma proteins enter the airway lumen without being sieved. These data indicate that inflammatory stimulus-induced extravasation, lamina propria distribution and paracellular epithelial passage of plasma occur with minimal size-selectivity. Inferentially, the full immunological capacity of plasma proteins may readily be made available at the surface of human intact airway mucosa

Nasal neutrophil activity and mucinous secretory responsiveness in COPD.

Patients with chronic obstructive pulmonary disease (COPD) frequently report nasal symptoms. In the present study, we have examined whether or not COPD is associated with any nasal inflammation. Plasma exudation evoked by histamine challenges has been employed to improve the recovery of inflammatory indices in nasal lavage fluids. In 23 COPD-patients and 26 healthy subjects, all without history or signs of allergic rhinitis, nasal polyposis, or chronic rhinosinusitis, nasal saline-lavages were performed with and without histamine. alpha2-Macroglobulin, fucose, eosinophil cationic protein (ECP) and myeloperoxidase (MPO) were determined as indices of plasma exudation, mucinous secretion, eosinophil activity and neutrophil activity, respectively. The difference in MPO-levels between the histamine and the saline lavage was greater in COPD patients compared with healthy subjects (P<0·05). Also, COPD patients reporting nasal symptoms presented an increase in MPO at histamine challenge (P<0·05, cf. saline) and greater differences in MPO and fucose, respectively, between the histamine and the saline lavage (P<0·05, cf. patients without symptoms). We conclude that COPD is not associated with any marked nasal inflammation. However, our observation on increased MPO-levels at histamine challenge suggests some degree of increased neutrophil activity in this condition. Furthermore, when associated with nasal symptoms, COPD may be associated with an increased nasal secretory responsiveness

Comparison of Exact and Approximate methods for the Vehicle Routing Problem with Time Windows

This paper presents a comparison of two approaches for solving the vehicle routing problem with time windows (VRPTW). Scheduling of vehicles for pickup and delivery is a common problem in logistics and may be expressed as VRPTW, for which both exact and approximate techniques are available. It is therefore interesting to compare such techniques to evaluate their performance and figure what is the best option based on the instance features and size. In this work, we compared Mixed Integer Linear Programming (MILP) with Set-Based Particle Swarm optimization (S-PSO). Both algorithms are tested on the full 56 instances of the Solomon dataset. The results show that the two algorithms perform similarly for lower number of customers while there are significant differences for the cases with higher number of customers. For higher number of customers MILP consistently performs as good as or better than S-PSO for the clustered data, both with short and long scheduling horizons, while the S-PSO outperforms MILP in most cases with random and mixed random clustered data with long scheduling horizons. Furthermore when the algorithms perform the same with regards to the main objective (number of vehicles), MILP generally achieves a better result in the second objective (distance traveled)