Normal growth variance by Z scores should be considered when interpreting the growth inhibitory effect of inhaled corticosteroids.

Abstract

Randomized clinical trials suggest that long-term inhaled corticosteroid (ICS) treatment significantly inhibits growth velocity (GV) assessed by centimeters/year (cm/year) in primarily prepubescent, mild asthmatics. However, several observational studies measuring normal growth variance by Z score suggest the absence of the ICS inhibitory effect. To demonstrate the generalizability of ICS growth inhibition in cm/year by establishing whether this measure exceeds the expected normal changes in GV by Z score for similar age and sex. This was a retrospective, observational study comparing height and GV across a 2 year period in asthmatics aged 2-10 years, receiving ICS therapy (Group 3) with non-asthmatics, and non-ICS asthmatics (Groups 1 and 2), respectively. Generalized linear model procedure compared GV measures after adjustment for age, gender, and dependence of group differences on the age of the child. Before initiation of ICS therapy at baseline, Group 3 patients (n = 22) were shorter than Groups 1 (n = 67) and 2 (n = 44) by mean height in cm, and height for age Z score in the adjusted model (p < .05). GV was also significantly reduced in Group 3 after initiation of ICS therapy versus Groups 1 and 2 by 1.0-1.5 cm/year, respectively, p < .05, but not significantly in comparison to expected normal GV variance determined by Z score, p ≥ .05. Our findings suggest the need to consider normal growth variance by Z scores in addition to absolute changes (cm/year) when interpreting the inhibitory effect of ICS on GV. Larger sample size studies will be necessary to confirm our findings.