The effect of racial origin on total body water volume in peritoneal dialysis patients

Peritoneal dialysis adequacy is typically assessed by urea clearance corrected for total body water (TBW) on the basis of anthropomorphic equations, which do not readily take into account changes in body composition, which may vary between ethnic groups. To determine whether ethnicity could affect estimates of peritoneal dialysis adequacy, we compared TBW estimated by anthropomorphic equations and that measured by multifrequency bioimpedance spectroscopy.

We calculated TBW in 600 healthy adult peritoneal dialysis outpatient attending two tertiary university hospitals serving an inner-city multiethnic population who had TBW measured by multifrequency bioimpedance spectroscopy performed.

600 adult peritoneal dialysis patients were studied: mean age, 56.7 ± 0.6 years; 54.2% men; 29.7% diabetic; mean body mass index, 26.1 ± 0.2; 47.3% Caucasian; 29.2% South Asian; 12.8% African/Afro-Caribbean. Total body water was calculated using several anthropomorphic equations and was higher than that calculated MEASURED BY MF-BIS for all ethnic groups, apart from African/Afro-Caribbeans, with the greatest difference between Watson calculated TBW and multifrequency bioelectrical impedance spectroscopy 12.3 ± 0.6% for the South Asians, 9.0 ± 2.6% for Far Eastern Asians, 2.8 ± 0.6% Caucasians, and -0.2 ± 1.5% for African/Afro-Caribbeans.

In this United Kingdom-based multiethnic population, body composition differed particularly for the South Asian patients compared with Caucasians and African/Afro-Caribbeans. Overestimation of TBW by anthropomorphic-based equations would lead to a lower calculation of Kt/V(urea), which may lead to changes in peritoneal dialysis prescription to achieve clinical standard targets and also affect studies examining the relationship between Kt/V and survival.