Establishment of Reference Intervals for Eight Steroid Hormones in Korean Adults Using LC-MS/MS: Impact of Outlier...

Reference intervals for steroid hormones can vary significantly depending on the statistical approach used.

We established reference intervals for eight steroid hormones in 111 Korean females and 113 Korean males aged 18-49 years. Outlier detection was performed using both Tukey's fence criteria and the Reed-Dixon method. Sex- and age-stratified reference intervals were determined using a robust method after exclusion of outliers identified by Tukey's fence criteria. These intervals were compared with those derived using a nonparametric approach.

Depending on the hormone, the proportion of outliers identified by Tukey's fence criteria ranged from 0% to 17.6%, whereas the Reed-Dixon method rarely detected extreme outliers. The reference intervals derived using Tukey's fence criteria were generally consistent with previously reported values in Caucasian populations. A total of 12.0% of Korean males had testosterone concentrations below 10.4 nmol/L (300 ng/dL), the cutoff value for low testosterone according to the American Urological Association guidelines. In contrast, the nonparametric method with Reed-Dixon outlier detection yielded a lower reference limit of 0.80 nmol/L for testosterone, which would be considered pathologically low in adult males.

Our study highlights the importance of careful selection of the reference population, outlier exclusion method, and statistical approach when establishing reference intervals for steroid hormones.