Prediction of the outcome of growth hormone therapy in children with idiopathic short stature: A multivariate discriminant analyis

Abstract

Objective: To identify, with the use of pretreatment clinical data, the children with idiopathic short stature responsive to treatment with growth hormone (GH). Design: Open, prospective study in a university hospital. Subjects: Patients admitted to the study met the following criteria: birth weight at least 2.5 kg, no sign of dysmorphic disease, stature less than the 3rd percentile for chronologic age (CA), linear growth velocity (GV) less than the 25th percentile for bone age (BA), no sign of puberty, maximal GH response to pharmacologic stimulation greater than 10 μg/L, no evidence of organic disease, treatment with daily subcutaneous administration of GH at a dose of 12 to 16 IU/m2 per week. Main outcome measures: Eight pretreatment growth variables and the increase of GV after 6 months of therapy were measured. Children with a change in GV that was greater than 2.5 cm/yr after 6 months of GH therapy were considered responders to GH. Results: We studied 67 patients (44 boys). Forty patients (60%) were responders. With univariate analysis the variables found to have predictive value were GV (z score for gender and CA), bone age (z score for gender and CA), and percentage of ideal body weight. These variables were employed in a multivariate discriminant analysis. Growth velocity and BA showed the best independent discriminant significance in predicting responsiveness to the initial 6 monthsof GH therapy. The obtained equation was as follows: Score = -0.40 + 0.92X1 -0.87X2, where X1 is the GV z value for CA and X2 is the BA z value for CA). Using this scoring system, we obtained a specificity of 96.3% and a sensitivity of 92.5% in predicting responsiveness to GH (chi-square with Yates correction, 48.2; p <0.001). Conclusions: Discriminant analysis may permit the pretreatment prediction of responsiveness to the initial 6 months of GH therapy in short children without GH deficiency. (J PEDIATR 1995;126:905-9)