Reliability of percentage ideal weight for height

Abstract

Aims-To assess the reliability of percentage ideal weight for height (%WFH) as a measure in children. The expression of body weight as a percentage of ideal weight for height, gender, and age (%WFH) has been suggested by the American Cystic Fibrosis Foundation as a useful measure of nutritional status in children with cystic fibrosis (CF). Methods-Forty1 It is also used regularly as an outcome measure in CF research and as a measure of nutritional status in other areas of paediatrics including liver disease and oncology. [2][3][4][5] %WFH has the advantage of integrating both weight and height in the same measure and can easily be calculated. However, we have noticed variability between individuals in the calculation of %WFH. A comprehensive literature review has failed to identify any work on the reliability of this measure. Therefore, the aim of this study was to investigate the reliability of using %WFH as a measure of nutritional status. MethodsFifty two members of UK CF Dietitians Interest Group were sent a questionnaire examining the type of measures which they used to assess nutritional status. If they used %WFH they were asked how frequently they did so and by which method.Each dietitian was asked to complete %WFH calculations based on the following details of six CF patients: date of birth, sex, height, weight, and the date on which the height and weight were taken. Growth charts were provided, as were the US CF Foundation instructions for calculating %WFH:1. Plot the height on the growth chart and determine height centile. 2. Determine the weight that corresponds to the same point on the centile chart as the height. 3. Divide actual weight by ideal weight, then multiply by 100. Eleven of 44 dietitians were contacted a month after receiving the first %WFH calculation sheet, and asked to repeat the calculations based on the same data without referring back to their previous calculations.Means, standard deviations, and ranges of the results obtained for each patient and for each dietitian were calculated. ResultsForty four of the 52 dietitians completed the questionnaire. The majority (35/44) used %WFH as a measure of nutritional status. Of these, 14 assessed %WFH annually and nine at each clinic visit. Height and weight centile measurements were recorded at each clinic by 41/44. The US CF Foundation method for calculating %WFH was used by 22/35 dietitians and the Cole Slide Rule was used by 9/35. %WFH calculations were completed by 42/52. The range of estimates for each of the six patients varied by 16.5 to 40 percentage points (mean 27.8; fig 1). On average, 25% of the %WFH calculations were more than two percentage points either side of the mean, and 8.5% were more than five percentage points either side of the mean.Eleven of the dietitians completed the second set of calculations. The range of estimates for each of the six patients varied by between 13 and 24 percentage points (mean 16.8). For each of the 11 dietitians the average diVerence between the two sets of results was calculated and th...

Standards of care for patients with cystic fibrosis: a European consensus

“…or Z scores. Percentage weight for height, weight for age and height for age are often used when expressing the nutritional status of children though their reliability has been questioned [17]. BMI percentile charts should also be used for children to give a more accurate interpretation of nutritional status especially in the stunted individual.…”

Evaluation of body mass index percentiles for assessment of malnutrition in children with cystic fibrosis

“…Also, calculation of %IBW is complex and requires steps of visual estimation or approximate calculation by polynomial equations. In this regard, wide inter-and intra-examiner variations have been reported, making %IBW values unreliable (Poustie et al, 2000).…”

A chart to link child centiles of body mass index, weight and height

“…Take for example the percentage ideal weight for height (%WFH), recommended for assessing the nutritional status of children with cystic fibrosis (CF; Ramsey et al, 1992). Dietitians have great difficulty calculating it, with the mean variability in %WFH between 42 CF dietitians asked to assess six patients reaching 28% (Poustie et al, 2000).…”