Validity of impedance-based equations for the prediction of total body water as measured by deuterium dilution in Cameroonian HIV-infected patients treated with antiretroviral treatment

Summary Background & aims No information is available on the validity of impedance-based equations for the prediction of body composition in Cameroonian HIV-infected patients treated with antiretroviral drugs. Equations for the prediction of total body water (TBW) have the tendency to be population-specific, and this may be due to biological factors, such as variable body geometry and physiological state. We tested the validity of equations derived from different racial backgrounds for predicting TBW from bioelectrical impedance analysis measurements. Method The TBW content of 56 Cameroonian HIV patients (19 men and 37 women) treated with the first-line ARV regimen was measured by deuterium dilution and compared with those predicted by 12 equations developed respectively in samples of white, black, black and white, or unspecified racial background subjects. Results Pure errors in predicting TBW showed acceptable value for all the equations tested. Four equations (three from whites and one from blacks and whites) yielded a non-significant bias; however, equation H which presented the narrower 95% confidence interval and the smaller pure error was recommended for the prediction of TBW in Cameroonian HIV-infected patients treated with antiretroviral drugs. In all other cases, we observed either an overestimation or underestimation of TBW with variable bias values. Conclusion The absence of a clear trend in cross-validation among equations according to their origin and the probable effect of physiological state should encourage further exploration of the causes of the lack of validity.