Reference ranges for testosterone assays vary significantly among labs.

[Nelson Vergel]

Le M, Flores D, May D, Gourley E, Nangia AK.

Current Practices of Measuring and Reference Range Reporting of Free and Total Testosterone in the United States.

J Urol. http://www.sciencedirect.com/science/article/pii/S0022534715054464

PURPOSE: The evaluation and management of male hypogonadism should be based on symptoms and serum testosterone levels. Diagnostically, this relies on accurate testing and reference values. Our objective was to define the distribution of reference values and assays for free and total testosterone by clinical laboratories in the US.

MATERIALS AND METHODS: Upper and lower reference values, assay methodology, and source of published reference ranges were obtained from labs across the country. A standardized survey was reviewed with laboratory staff via telephone. Descriptive statistics were used to tabulate results.

RESULTS: 120 laboratories from 47 states were surveyed. Total testosterone was measured in-house at 73% of labs. The remaining sent their studies to larger centralized reference facilities.

The mean lower reference value for total testosterone was 231 ng/dL (range 160-300, SD 46) and the mean upper limit was 850 ng/dL (range 726-1130, SD 141). Only 9% of labs performing in-house total testosterone testing created a reference range unique to their region, while others validated their instrument's recommended reference values with a small number of internal test samples.

For free testosterone, 82% of labs sent testing to larger centralized reference labs that used equilibrium dialysis and/or liquid chromatography with mass spectrometry. Remaining labs used published algorithms to calculate serum free testosterone.

CONCLUSION: Reference ranges for testosterone assays vary significantly among labs. They are predominantly defined by limited population studies of men with unknown medical and reproductive history. These poorly defined and variable reference values, especially lower limit, affect how clinicians determine treatment.

 

[HarryCat]

Looks like they repeated this study that Morgentaler and Lazarou did 10 years ago:

ORIGINAL RESEARCH—ENDOCRINOLOGY: Wide Variability in Laboratory Reference Values for Serum Testosterone

ABSTRACT

Introduction.  The laboratory determination of testosterone levels consistent with a diagnosis of hypogonadism is complicated by the availability of multiple testosterone assays and varying reference ranges.

Aim.  To assess current laboratory practices regarding availability of testosterone assays and use of reference values.

Methods.  A telephone survey of 12 academic, 12 community medical laboratories, and one national laboratory.

Main Outcome Measures.  Types of androgen assays offered and determination of reference values.

Results.  All of the academic and eight of the community centers performed total testosterone testing. Free testosterone was performed in-house by six of the 12 academic and one community center. Testing for bioavailable testosterone, free androgen index, and percent free testosterone was performed in-house by no more than two centers. There were eight and four different assays used for total and free testosterone, respectively. One national laboratory offered equilibrium dialysis measurement of free testosterone. Of the 25 labs, there were 17 and 13 different sets of reference values for total and free testosterone, respectively. The low reference value for total testosterone ranged from 130 to 450 ng/dL (350% difference), and the upper value ranged from 486 to 1,593 ng/dL (325% difference). Age-adjusted reference values were applied in four centers for total testosterone and in seven labs for free testosterone. All reference values were based on a standard statistical model without regard for clinical aspects of hypogonadism. Twenty-three of the 25 lab directors responded that clinically relevant testosterone reference ranges would be preferable to current standards.

Conclusions.  Laboratory reference values for testosterone vary widely, and are established without clinical considerations. Lazarou S, Reyes-Vallejo L, and Morgentaler A. Wide variability in laboratory reference values for serum testosterone. J Sex Med 2006;3:1085–1089.