Comparison of height for age and height for bone age with and without adjustment for target height in pediatric patients with CF

Abstract

Background: Height is a strong prognostic factor in cystic fibrosis (CF) and is usually compared to reference values of healthy children by expressing height as a z-score height-for-age (HFA). However, HFA does not take into account a potential delay in bone age (BA) and the genetic potential of the child and could therefore result in misclassification of short stature.

Methods: In 169 children with CF height, BA and target height (TH) were assessed. HFA, height for bone age (HBA), HFA adjusted for target height (HFA/TH) and HBA adjusted for target height (HFA/TH) were determined and children were categorized according to these four methods.

Results: Mean z-scores of the four methods ranged from -0.1 ± 0.8 (HBA/TH) to -0.5 ± 1.0 (HFA). Prevalence of short stature (z-score <-2 SD) determined by HFA (8%, n=14) was higher than when HBA, HFA/TH (both 5%, n=8) and HBA/TH (1% n=1) were applied.

Conclusion: The method used to classify height affects outcome on a group level and for individual patients. Target height and bone age are likely to have added value in the interpretation of height in patients with CF.