Changes in Total Testosterone Assay Reference Ranges

Effective Thursday, March 3, 2011, the University of Iowa Hospitals and Clinics (UIHC) core laboratory will change the reference range for plasma "TESTOSTERONE-TOTAL" (EPIC # LAB124). This follows from a change to a new version of the immunoassay, which also allows for the ability to measure down to 5 ng/dL instead of the current lower limit of 12 ng/dL. Values less than 5 ng/dL will be resulted as "< 5 ng/dL". This assay is not typically recommended for girls 18 years and younger due to the low concentrations of testosterone generally present (often < 5 ng/dL).

The reference range for boys 18 years old and younger are the same but the ranges for adult males and females now include separate ranges for 19-49 years old and 50 years and older.

The new ranges for adults are:

Adult males: 19-49 years old 249-836 ng/dL
  50 years and older 193-740 ng/dL
Adult females: 19-49 years old 8-48 ng/dL
  50 years and older 2-41 ng/dL

Questions should be directed to Matthew Krasowski, MD, PhD, Medical Director of the Clinical Chemistry Laboratory (384-9380,