Validation of referral criteria for growth monitoring in Flanders based on height at the start of GH therapy in children with growth hormone deficiency and Turner syndrome

Background/Aims: Length and weight of all children in Flanders are monitored every three years at school from the age of 3 years. The current criteria used for referral to specialized care are: height SDS < -2.5, height SDS between -2 and -2.5 SDS with a height SDS adjusted for parental height < -1.64, or a decrease in height SDS of more than 1 SDS in the past 3 years. The aim of this study is to investigate the sensitivity of the Flemish referral criteria to detect idiopathic/congenital growth hormone deficiency (GHD) and Turner syndrome (TS). Methods: A cross-sectional analysis of data from children with idiopathic/congenital GHD and girls with TS included in the BELGROW register – a national register of all GH treated children – from January 2018 through December 2020. Height at the start of GH treatment and 2-3 years before GH treatment and parental heights (reported or measured) were retrieved from the database. Height SDS adjusted for parental height was calculated according to Hermanussen & Cole. The referral analysis only included prepubertal children below 10 years of age. Results: In the 112 children with GHD (78 male), GH treatment was started at a median age of 8.86 years (P10, P90: 2.86, 13.11) and a median height SDS of -2.99 (-4, -1.77). In the 43 girls with Turner syndrome this was 9.63 years (5.42, 14.44) and a height SDS of -2.79 (-3.77, -1.83). In the 97 children younger than 10 years of age, a height SDS < -2.5 was reported in 56 (76 %) out of 74 children with GHD and in 14 (61 %) out of 23 girls with TS. The SDS adjusted for parental height was < -1.64 in 60 (81 %) and 18 (78 %) respectively. In children older than 3 years with data on pre-treatment height, 5 (10 %) out of 49 with GHD and 1 (6 %) out of 17 with TS had a height decrease > 1 SDS before the start of GH treatment. Conclusion: In Belgium, GH treatment is started relatively late in children with congenital/idiopathic growth hormone deficiency and Turner syndrome, despite systematic growth monitoring at school. Height SDS adjusted for parental height was the most sensitive criterium for auxological detection of growth hormone deficiency and Turner syndrome, stressing the need of collection of parental height in school health surveys