Validation of bioimpedance spectroscopy to assess acute changes in hydration status.

PURPOSE: To validate bioimpedance spectroscopy (BIS) as a field method for measuring small, acute changes in extracellular water (ECW) during a fluid fast/rehydration manipulation. METHODS: Seventeen young adults (15 female, 2 male) participated in a 4-d fluid fast/rehydration protocol designed to induce acute changes in ECW. ECW change (DeltaECW), measured by bioimpedance spectroscopy (BIS-DeltaECW), was compared with DeltaECW, measured by bromide dilution (Br-DeltaECW), and change in body weight (DeltaBW). RESULTS: Regardless of hydration status, BIS-DeltaECW and Br-DeltaECW were similar; during dehydration, the mean difference between these two methods was 0.16 kg (P=0.61), and during rehydration, the mean difference was 0.58 kg (P=0.06). Assuming that DeltaECW=DeltaBW, DeltaECW as estimated from DeltaBW differed significantly from Br-DeltaECW, but not from BIS-DeltaECW. In addition, BIS-DeltaECW correlated significantly with DeltaBW (r=0.57 and 0.65 during dehydration and rehydration, respectively). However, the magnitude of DeltaECW impacted the accuracy of BIS-DeltaECW because BIS measures tended to overestimate DeltaECW at values between 0.0 and 1.0 kg and to underestimate changes at values above 1.0 kg. CONCLUSION: These findings suggest that BIS provides an accurate estimate of DeltaECW compared with bromide dilution during short-term changes in hydration.

Body cell mass repletion and improved quality of life in HIV-infected individuals receiving oxandrolone.

BACKGROUND: The aim of this study was to measure changes in body cell mass (BCM) and quality of life in HIV-infected individuals undergoing oxandrolone therapy. Previous studies on oxandrolone have neither quantified changes in BCM using criterion methods nor quality of life using an HIV-specific instrument. METHODS: Twenty-five HIV-infected patients (15 with an AIDS diagnosis) on standard antiretroviral and nutrition management were studied before and an average of 18.6 weeks after the initiation of oxandrolone therapy, as prescribed by their primary care physician for the treatment of weight loss. BCM was estimated from intracellular water measured by multiple dilution. Lean soft tissue mass (LTM) was measured by dual-energy X-ray absorptiometry. Quality of life was evaluated by the Functional Assessment of HIV Infection (FAHI) questionnaire. RESULTS: Significant gains in body weight (2.6 +/- 3.0 kg; p < .0001), BCM (3.6 +/- 3.0 kg; p < .0001), and LTM (3.0 +/- 2.9 kg; p < .0001) occurred over an average course of 18.6 weeks of treatment. Overall quality of life improved (p = .056) and appetite improved (p = .032), both of which were positively associated with weight gain (p = .040 and p = .022, respectively). CONCLUSIONS: This is the first study involving oxandrolone therapy in HIV infection to document changes in quality of life and BCM, the metabolically active component of lean body mass that reflects nutritional status better than other more global body composition parameters. Nutritional status and quality of life can improve in HIV-infected individuals receiving a combined therapeutic approach that includes oxandrolone.

Reproducibility of DXA in obese women.

Dual-energy X-ray absorptiometry (DXA) measurements were analyzed using two versions of software (Hologic V8.1a and V8.21) to compare the short- and long-term precisions of the measurements. Software V8.21 was designed by the manufacturer to better address magnification effects on estimations of soft tissue lean mass. Twenty weight-stable, obese postmenopausal Caucasian women aged 40-70 yr participated in the study. Total and regional body composition measurements were obtained at baseline and after 3 mo, using a fan beam Hologic QDR 4500A absorptiometer. For the estimation of precision, duplicate scans obtained on the same day for nine women were analyzed using both versions of the software. The correlations between duplicate scans ranged from 0.886 to 0.998 and were similar between software versions. The CVs for fat and lean weights and bone mineral content (BMC) were 1.2%, 1.1%, and 1.7%, respectively, for software V8.21 compared to 1.3%, 1.3%, and 2.1%, respectively, for V8.1a. Systematic differences were found between software versions with higher values for fat and lean weights for software version V8.21. The 3-mo, long-term reproducibility of body composition estimates from DXA was only slightly less than short-term reproducibility for both software versions (coefficient of variation [CV] range from 1.3% for BMC weight to 11.0% for arm fat). Software V8.21 yielded smaller percentage mean differences between scale and DXA-estimated weights (-2.4% and -7.2% at baseline and -2.9% and -7.6% at 3 mo, respectively) and higher fat and lean weights (49.12 and 47.1 kg and 49.6 and 44.6 kg, respectively) than V8.1a. Reproducibility of all variables was comparable between software versions.