Dual-energy X-ray absorptiometry is the method of choice to assess body composition in COPD.

BACKGROUND AND OBJECTIVE: Mortality and morbidity in COPD have been related to reduced FEV1 as well as indices of body composition. Different techniques used to evaluate body composition may vary in accuracy, particularly in conditions with altered fluid balance such as COPD. We hypothesized that direct measurement of fat-free mass index (FFMI) by dual-energy X-ray absorptiometry (DEXA) would provide superior assessment of body composition in COPD. METHODS: We measured body composition in 31 patients with COPD randomly selected from a teaching hospital clinic. To estimate total body water (TBW) and FFMI, skin-fold anthropometry, bioelectrical impedance analysis (BIA) with Schols and Lukaski equations as well as DEXA, total body potassium by whole-body gamma-counting (TBK) and in vivo neutron activation analysis were used. Combined body composition methods providing precise estimations of TBW were used for comparisons. Bland-Altman analyses, ANOVA and chi2-testing were used to examine data. RESULTS: Mean BMI was 27.6 +/- 5.34 kg/m2 (mean +/- SD). Estimations of TBW were similar using Schols BIA or by using combined body composition methods. FFMI did not vary significantly between grades of COPD severity but was significantly different when assessed using DEXA and other methods. Calculated FFM hydration was significantly different from the fixed hydration factor used to calculate FFMI from BIA TBW (P < 0.05). CONCLUSION: The Schols BIA method incorporates a fixed hydration factor that may lead to an erroneous estimation of FFMI with ensuing clinical implications. DEXA can be used to obtain accurate and comprehensive assessments of body composition and should be the preferred investigation in COPD.

The effects of drug-sensitive and drug-resistant Trypanosoma congolense infections on the pharmacokinetics of homidium in Boran cattle.

Two groups of five Boran (Bos indicus) cattle were infected with one of two populations of Trypanosoma congolense; one drug-sensitive (IL1180), and one drug-resistant (IL3330). The animals were then treated intramuscularly with homidium bromide at a dose rate of 1.0 mg kg(-1) bodyweight 7 days after trypanosomes were detected in the peripheral blood of all the five animals in each group. Following treatment of cattle infected with drug-sensitive trypanosomes, parasites could no longer be detected in the bloodstream of four out of five cattle after 24 h, and after 48 h for the fifth animal. The animals remained aparasitaemic up to the end of the observation period of 90 days and serum drug concentrations determined by enzyme-linked immunosorbent assay (ELISA) remained above the detection limit of 0.1 ng ml(-1) for the entire period. Following treatment of cattle infected with drug-resistant trypanosomes, parasites did not disappear from the bloodstream in any of the five animals. The rate of drug elimination was greater in cattle infected with drug-resistant trypanosomes and the drug was no longer detectable approximately 3 weeks after treatment. Non-compartmental pharmacokinetic analysis showed that the values for t(12)beta of 75.5 +/- 16.9 h, the area under the curve (AUC(0-infinity)) of 1.33 +/- 0.156 microg h ml(-1) and the MRT(0-infinity) of 32.8 +/- 4.45 h obtained in cattle infected with the drug-resistant trypanosome population were significantly lower than the values of 424 +/- 146 h for t(12)beta, 1.67 +/- 0.233 microg h ml(-1) for AUC(0-infinity) and 297 +/- 159 h for MRT(0-infinity) obtained in cattle infected with the drug-sensitive population. The persistence of drug-resistant infections in cattle following homidium treatment was associated with more rapid drug elimination than in those in which infections with drug-sensitive parasites were cleared by the drug.