From the article:
A large study of more than 9,000 men has established harmonized reference ranges for total testosterone in men that when applied to assays that have been appropriately calibrated will effectively enable clinicians to make a correct diagnosis of hypogonadism, according to a new study published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism.
[…]
Researchers used the results from both measurements to generate harmonized values, which were in turn used to derive standardized, age-specific reference ranges overall. The harmonized normal range for testosterone in a non-obese population of European and American Men, 19-39 years, is 264-916 ng/dL.