For a study, researchers sought to assess the performance of weight-for-length and BMI as predictors of malnutrition in children with cystic fibrosis (CF). The Cystic Fibrosis Foundation Patient Registry was used to evaluate pediatric anthropometric data. Weight-for-length z score (WFLZ) or body mass index z score (BMIZ)≤–1 were used to determine undernutrition (15th-percentile). Group 1 was made up of people who had both BMIZ and WFLZ >–1; group 2 was made up of BMIZ ≤–1 and WFLZ >–1; group 3 was made up of BMIZ >–1 and WFLZ ≤–1, and Group 4 was made up of BMIZ and WFLZ ≤–1. Using generalized estimating equations, investigators evaluated group differences in length-for-age-Z across ages 2-24 months. In addition, the link of the group at age 2 months with BMIZ <–1 at age 6 years was investigated using logistic regression, which was controlled for demographic and illness variables.

Overall, 163,482 anthropometric measures were collected from 12,640 people, with 16.8% showing undernutrition at 2 months. With advancing age, discordance (1.5% -10%) became less prevalent. Between birth and 24 months, length-for-age-Z was lower in group 2 than in groups 1 and 3 (P<.05). Shorter people had a decreased risk of being WFLZ-defined undernourished at 2 months (OR 1.5, CI 1.4-1.6, P<.001). At 6 years of age, the risk of undernutrition was higher in Group 2 than in Group 3 (OR 1.9 vs. 1.0, P<.001). 

Children with cystic fibrosis diagnosed as undernourished by BMIZ but not by WFLZ had a higher chance of being undernourished later in life. In addition, infants with a low BMIZ but a normal WFLZ tended to be shorter, suggesting that BMIZ may be a more robust indicator of malnutrition than WFLZ in shorter babies.

Reference:www.jpeds.com/article/S0022-3476(21)01157-4/fulltext

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