Special Communication
Update: Changes to Testosterone (Free & Total) Testing and Reporting
As of July 21, 2019, Free Testosterone testing (TFTEST – formerly FTESTO) is now being referred to an external reference laboratory.
Compared to the previously used internal methods, the external laboratory uses different methodologies and reports results in different units of measure for Free Testosterone.
Key points that affect the interpretation of these test results:
- Free Testosterone is reported in ng/dl, compared to pg/ml for the previous internal method.
- For comparison, 10 pg/ml is equivalent to 1 ng/dl.
- Because of these differences, test results from CCL versus the referral laboratory are not comparable in representations of trending result values over time.
For test results reported from July 21, 2019, to August 14, 2019, the Free Testosterone component will be corrected to clarify units of measurement.
The correction will not impact the test result; the result will be listed in the interpretative comment along with the reference range.
The corrected report will appear as follows:
Component
Reporting Example
Total Testosterone
See comment.
Interpretative comment:
The total testosterone result is 435 ng/dl, the reference range of Mayo Clinic Laboratories is ## to ## ng/dl.
Disregard the Cleveland Clinic reference range. Interpret the result using the reference range provided by the performing laboratory.
Results should not be compared to previously reported results using Cleveland Clinic’s assay due to differences in methodology.
Test performed by: Mayo Clinic Laboratories, Rochester, MN.
Testing performed by Liquid Chromatography-Tandem Mass Spectrometry.
Free Testosterone
See comment.
Interpretative comment:
The free testosterone result is 10.0 ng/dL, the reference range of Mayo Clinic Laboratories is ## to ## ng/dL.
Disregard the Cleveland Clinic reference range. Interpret the result using the reference range provided by the performing laboratory.
Results should not be compared to previously reported results using Cleveland Clinic’s assay due to differences in methodology.
Test performed by: Mayo Clinic Laboratories, Rochester, MN.
Testing performed by Equilibrium Dialysis.
% Free Testosterone
Not reported by Mayo Clinic Laboratories.
Any additional information will be included in a future Technical Update. If you have any questions about these changes, please contact Client Services for assistance.