Regional body composition: cross-calibration of DXA scanners--QDR4500W and Discovery Wi.

Differences exist in body composition assessed by dual-energy X-ray absorptiometers (DXAs) between devices produced by different manufacturers and different models from the same manufacturer. Cross-calibration is needed to allow body composition results to be compared in multicenter trials or when scanners are replaced. The aim was to determine reproducibility and extent of agreement between two fan-beam DXA scanners (QDR4500W, Discovery Wi) for body composition of regional sites. The sample was: 39 women 50.6 +/- 9.6 years old with BMI 26.8 +/- 5.5 kg/m(2), body fat 33 +/- 7%. Four whole body scans (two on each device) were performed over 3 weeks. Major variables were fat mass, nonosseous lean mass, and bone mineral content (BMC) for the truncal and appendicular regions. Extent of agreement was assessed using Bland and Altman plots. Both devices demonstrated good precision with mean test-retest differences close to zero for fat mass, nonosseous lean mass, and BMC of the truncal and appendicular regions. Evaluation of interdevice agreement revealed significant differences for truncal and appendicular BMC, nonosseous lean mass, and fat mass. The greatest interdevice difference was for truncal fat mass (0.69 +/- 0.60 kg). Differences in truncal and appendicular fat mass increased in magnitude at higher mean values. Furthermore, differences in truncal and appendicular fat mass were strongly related to BMI (R = -0.61, R = -0.55, respectively). In conclusion, in vivo cross-calibration is important to ensure comparability of regional body composition data between scanners, especially for truncal fat mass and for subjects with higher BMI.

Importance of cross-calibration when replacing DXA scanners: QDR4500W and Discovery Wi.

The aim of the study was to determine reproducibility and extent of agreement between 2 dual-energy X-ray absorptiometers (Hologic QDR4500W, Discovery Wi). The average age of the sample (n = 42) was 50.4 (SD = 9.9) years old and 27.1 (SD = 6.1) kg/m2 body mass index. Four scans were performed with each subject (2 on each device) over approximately 3 weeks. Whole body, proximal femur, and spine scans were performed at each visit. Major variables were whole body bone mineral content (BMC), fat mass, and nonosseous lean mass, and bone mineral density (BMD) of total proximal femur, femoral neck, total spine. Bland and Altman plots assessed the extent of the agreement. Regression analysis was used to develop correction equations if indicated. Both devices demonstrated good precision for whole body composition and BMD of central sites (< 1% different). Interdevice agreement was acceptable for BMD of central sites (< 1% different), but there were systematic differences for whole body composition between the 2 devices. It was concluded that when replacing an existing scanner with a new model, in vivo cross-calibration is important to ensure comparability of scan data, especially for whole body composition.

Subjective fatigue, influencing variables, and consequences in chronic obstructive pulmonary disease.

BACKGROUND: Fatigue is a common symptom of chronic obstructive pulmonary disease (COPD), but little is known about the specific nature of COPD-related fatigue and its impact on daily life. OBJECTIVES: To (a) describe characteristics of fatigue in people with COPD and (b) test a theoretically and empirically supported model of the relationships among subjective fatigue, dyspnea, functional performance, anxious and depressed moods, and sleep quality in people with COPD. METHODS: A cross-sectional descriptive study was conducted with 130 people with moderate to severe COPD. Measures included the following: a Numerical Rating Scale (NRS) for frequency, intensity, and distress of fatigue and dyspnea; Fatigue Assessment Instrument (FAI); Chronic Respiratory Disease Questionnaire (CRQ); Profile of Mood States (POMS); Pittsburgh Sleep Quality Index (PSQI); Functional Performance Inventory (FPI); and spirometry. Path analysis was used to examine the relationships among variables. RESULTS: Participants reported moderate amounts of fatigue, which was described as situation-specific, had considerable consequences, and was responsive to rest and sleep. Dyspnea was slightly greater than fatigue, as measured by the NRSs (p <.001), and there was a strong relationship between fatigue and dyspnea (r =.74, p < .001). Dyspnea, depressed mood, and sleep quality accounted for 42% of the variance in subjective fatigue. Fatigue, dyspnea, airflow obstruction, and anxious mood accounted for 36% of the variance in functional performance. CONCLUSIONS: Fatigue is an important problem that affects performance of daily activities in people with COPD. The relationships or interactions that exist among fatigue and other symptoms are complex.

Reversal of chronic obstructive pulmonary disease-associated weight loss : are there pharmacological treatment options?

Poor nutritional status is associated with an increased incidence of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD). While a number of factors have been shown to produce tissue catabolism, no single mechanism has been clearly identified as a primary cause for weight loss in patients with severe COPD. Without a clear understanding of the aetiology of weight loss, therapeutic strategies to reverse this process have historically been unsuccessful. A review of recent studies allows consideration of a model of mechanisms of weight loss. This model includes multiple pathways that may be activated singly or simultaneously to cause loss of weight, specifically lean body mass. These include energy imbalances, elevated levels of cytokines, tissue hypoxia and the effects of cocorticosteroid therapy. To date, interventional studies that have looked at newer pharmacotherapies such as growth hormone and anabolic steroids in patients with COPD who are losing weight have not demonstrated reversal of weight loss or improvement in nutritional status. Currently, early identification of patients at risk for weight loss and aggressive nutritional supplementation coupled with an exercise programme has demonstrated the greatest benefit. However, with increasing understanding of the mechanisms that may be implicated, new targets for therapies are being identified. Of particular research interest are molecules such as leukotrienes, hormones, tumour necrosis factor-alpha and acute-phase proteins, which are noted to be elevated in some patients with COPD-associated weight loss. Currently, inhibitors to some of these inflammatory substances are used therapeutically in other chronic illnesses such as rheumatoid arthritis and cancer cachexia. Future research may investigate their usefulness in COPD and direct new therapies that target the processes contributing to weight loss in these patients.