Establishment of Reference Intervals for Serum Insulin-Like Growth Factor I in Korean Adult Population

Abstract

Appropriate reference intervals of serum insulin-like growth factor I (IGF-I) is important for diagnosing and monitoring patients with growth hormone-related diseases. To establish reference intervals, adult individuals (n=1,334, 680 men and 654 women) were divided into six age groups (20-29, 30-39, 40-49, 50-59, 60-69, ≥70). Serum IGF-I was measured by chemiluminescence immunoassay (Liaison). Concordance of patient classification based on reference intervals, manufacturer's intervals, and standard deviation score (SDS) was evaluated. New reference intervals had higher upper and lower limits than those specified by the manufacturer. The agreement between classification using new reference interval and the manufacturer's reference interval, and that using new reference interval and SDS was 75.0% (weighted kappa, 0.17), 91.9% (weighted kappa, 0.51) in men and 91.0% (weighted kappa, 0.41), 92.5% (weighted kappa, 0.53) in women, respectively. Reference intervals should be established not only based on age and sex, but also on ethnicity and assay method.

Keywords: Insulin-like growth factor I; Luminescent measurements; Reference values.

Fig. 1

Individual data and comparison between the new reference intervals and reference intervals of Liaison insert. The black points indicate individual data. New reference intervals are shown in colored section (A: blue, men; B: red, women). Reference intervals of Liaison insert paper are shown in the grey section. Liaison insert paper only showed reference intervals until the age of 85 years. IGF-I, insulin-like growth factor I.