P.11.7 Prediction equations based on arm measurements may overestimate standing height in Duchenne Muscular Dystrophy (DMD) patients on glucocorticoid (GC) therapy

Abstract

Accurate height measurements (HM) are needed for evaluation of growth and nutrition status, calculation of medication doses, glomerular function, pulmonary function tests (PFT) and 6 min walk tests (6MWT). HM is unreliable in patients with inability to stand or joint or spinal deformities. Prediction equations for height based on arm span (AS) and ulnar length measurements have been established in healthy children. To date, there are no similar prediction equations for children with neuromuscular (NM) disorders. (1) To evaluate the bias in predicted height from Gauld’s (2004) equation based on AS (here, bias is defined as observed height minus predicted height); and (2) to correlate AS and segmental arm span (SAS) measurements with standing height (SH) in children with NM disorders. Cross sectional study of 50 males with DMD on GC and 19 males with NM disorders not on GC treatment (Non GC). SH, AS, SAS were measured. Subjects were 69 males with NM disorders with or without GC treatment (GC 0 N = 50, aged 8.8 ± 2.7 y; Non GC – N = 19, aged 8.3 ± 3.0 y). Gauld’s prediction equation based on AS overestimated SH by a mean of 1.68 ± 2.48 cm in GC group ( p p = 0.81). AS and SAS were highly correlated with SH in both groups (GC – AS & SH, r 2 = 0.97; SAS & SH, r 2 = 0.95; non-GC – AS & SH, r 2 = 0.98; SAS & SH, r 2 = 0.97). Our study verified the accuracy of Gauld’s equation based on AS in the non GC group and noted the overestimation of SH in the GC group. GC induced spine compression fractures and linear growth failure may affect SH in children with NM disorders on GC, thereby limiting the use of standard prediction equations for height in this population. Further studies to obtain accurate height prediction equations in NM patients on GC are warranted when accurate PFTs and 6MWTs are integral outcome measures for clinical care and research.