Variation in methods of predicting adult height for children with idiopathic short stature

Abstract

Objective: Recombinant human growth hormone (GH) is approved for treatment of children with idiopathic short stature, and endocrinologists often depend on algorithms to predict adult height. Because algorithm performance often is included in treatment decisions, we sought to evaluate agreement among height prediction formulas.

Methods: We identified 3 commonly used algorithms for height prediction, the Bayley-Pinneau, Roche-Wainer-Thissen, and Khamis-Roche methods. We constructed simulated samples of children with typical distributions of ages, heights, weights, bone ages, and parental heights seen in patients with idiopathic short stature, and we applied the algorithms to the simulated sample to determine whether predicted adult height was <160 cm for boys or <150 cm for girls (<1.2nd height percentiles for adults).

Results: We found substantial disagreement among algorithms in the proportions of simulated cases with predicted adult heights of <1.2nd percentile, a cutoff value that may influence GH treatment decisions. With the Bayley-Pinneau formula, 43% of boys and 81% of girls had predicted adult heights below this threshold; with the Khamis-Roche method, only 3% of boys and 0.2% of girls had predicted heights of <1.2nd percentile. Roche-Wainer-Thissen predictions were between those values. Overall agreement of the methods was poor (κ = 0.21) for boys and negative for girls.

Conclusions: Wide variation exists among formulas used to predict adult heights. Because these algorithms may be used in decisions regarding whether to initiate GH treatment and assessment of the efficacy of GH in research trials, it is important for parents, pediatricians, and investigators to recognize the considerable variation involved in height predictions.

Figure 1

Distributions of adult heights predicted by using 3 height prediction algorithms. Bars to the left of the red line represent predicted adult heights that are below the 1.2nd percentile for adult height (160 cm or 63 inches for men and 150 cm or 59 inches for women). The blue and pink bars (at extreme right) represent simulated samples that did not allow for height prediction with the BP algorithm because bone age was less than the value required for the algorithm.