title: Disagreement between height/weight classifications of underweight, normal weight, and obesity in peritoneal dialysis patients.
abstract: Peritoneal dialysis (PD) patients are classified as underweight, normal weight, or obese by height/weight indices including body mass index (BMI) and the body weight/desired weight (W/DW) ratio. We compared these classifications of degree of obesity in 378 women and 555 men on PD. We used these cut-off values: for underweight, BMI < or = 18.5 and W/DW < or = 0.9; for obesity, BMI > or = 30.0 and W/DW > or = 1.2. The W/DW values were calculated assuming first a small frame, then a medium frame, and finally a large frame for all subjects. Regardless of sex or skeletal frame, BMI correlated highly with W/DW (r value between 0.98 and 0.99); however, the range of BMI values corresponding by linear regression to the normal range of W/DW (0.9-1.2) was narrower than the range of "normal" BMI (18.5-30.0). Consequently, regardless of sex or skeletal frame, smaller fractions of the patient population were classified as underweight or obese by BMI standards than by W/DW standards. The degree of agreement of the classifications of subjects as underweight, normal weight, or obese by BMI and W/DW was evaluated by Cohen's kappa ratio. The kappa ratio varied between 0.47 and 0.58, indicating a reasonable--but not high--degree of agreement beyond chance. The highest kappa ratios were obtained assuming a medium skeletal frame for both women and men. Substantial discrepancies are observed in the classification of PD patients as underweight, normal weight, or obese by BMI and W/DW. Further research is needed to identify the height/weight index that has the strongest association both with clinical outcomes and with other, more precise measurements of body fat content.
authors.affiliation: Medicine Service, New Mexico Veterans Affairs Health Care System, and Department of Medicine, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Tzamaloukas
authors.forename: G H
authors.initials: GH
authors.lastname: Murata
authors.forename: J E
authors.initials: JE
authors.lastname: Hill
authors.forename: A
authors.initials: A
authors.lastname: Leger
authors.forename: L
authors.initials: L
authors.lastname: Macdonald
authors.forename: S
authors.initials: S
authors.lastname: Baron
authors.forename: R M
authors.initials: RM
authors.lastname: Hoffman
mesh_terms: D001824:Body Constitution; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000145:classification*; D010530:Peritoneal Dialysis; D013851:Thinness / Q000145:classification