Early attained weight and length predict growth faltering better than velocity measures in infants with CF

Background: CF infants often do not grow as expected which adversely affects later clinical outcomes, thus sensitive early measures of growth deficiency are important. This study compared attained growth for age with velocity standards to determine which better predicts growth deficits at 24 months of age.

Methods: Growth deficiency in infancy based on weight and length velocity, and attained growth was calculated for 1992 infants in the US CF Foundation National Registry using the World Health Organization (WHO) and US growth standards. One, two and three month increments were used for calculating velocity and pooled for each age interval. Sensitivity and specificity of early indicators to predict growth deficiency at 24 months were calculated.

Results: Observed prevalence of weight deficiency (<10th percentile) during the first year of life was 26.8% higher (95% CI=(25.6, 28.1%), p<0.001) on average when measured by attained weight for age than velocity. Attained weight for age at four months was a more sensitive predictor of diminished weight for age (<10th percentile) at 24 months (sensitivity=100%, 95% CI=(87, 100%)) than weight velocity (sensitivity=40%, 95% CI=(23, 59%)). Attained length at four months was more sensitive to detecting subsequent stunting (<10th percentile length for age) (77%, 95% CI=(62, 87%)) than length velocity (30%, 95% CI=(19, 45%)).

Conclusions: In CF infancy, attained weight or length is more sensitive than velocity-based definitions for predicting subsequent diminished growth.