 ### Description

Equations for estimating total body water that were developed in healthy adults tend to underestimate the total body water in hemodialysis patients. Chertow et al developed an equation for predicting total body water based on analysis of a population of patients undergoing hemodialysis. The authors are from Brigham and Women's Hospital and Fresenius Medical Care, Inc.

Population characteristics (given in Table 1, page 1579):

(1) The mean age was 60 years.

(2) The male to female ratio was 53%:47%.

(3) 45% Caucasian, 47% African American, 6.5% Hispanic

(4) Diabetes was present in 37%.

Parameters:

(1) age in years

(2) gender

(3) height in cm

(4) weight in kilograms

(5) diabetic status

(6) weight * weight

(7) age * gender

(8) gender * weight

(9) age * weight

(10) height * weight

 Parameter Finding Points gender male 1 female 0 diabetic status present 1 absent 0

total body water in kilograms =

= (-0.07493713 * (age in years)) - (1.01767992 * (points for gender)) + (0.12703384 * (height)) - (0.04012056 * (weight)) + (0.57894981 * (points for diabetes)) - (0.00067247 * (weight) * (weight)) - (0.03486146 * (age in years) * (points for gender)) + (0.11262857 * (points for gender) * (weight)) + (0.00104135 * (age in years) * (weight)) + (0.00186104 * (height) * (weight))

where:

• The first equation in Table 2, page 1580 uses 0.0186104 as the factor for (height) * (weight). The beta value in the listing above is 0.00186104, which is required to get valid results.

Performance:

• The results of the equation were comparable to findings from body impedance analysis.

• Equations developed in healthy adults (Watson, Hume-Weyer) tended to underestimate the total body water in this population by 3-4 kilograms.

Limitations:

• Regression equations may sometimes not transport to groups that differ significantly from the original population.