8551 Comparability of Free Testosterone Measurements

Abstract Disclosure: H. Zhou: None. O. Sugahara: None. U. Danilenko: None. H.W. Vesper: None. Assessment of free testosterone (FT) has been recommended as a biomarker for diagnosis and management of hypogonadism and female hyperandrogenism. Reliable laboratory measurements are essential for properly diagnosing and treating these diseases. FT is currently measured using direct commercial immunoassays, assays using equilibrium dialysis (ED) or other separation techniques, or estimated by calculating free testosterone (cFT) using different formulas based on the levels of total testosterone and sex hormone binding globulin (SHBG). There are concerns about the accuracy and reliability of current methods that may negatively impact correct detection, treatment, and prevention in patient care. CDC’s Clinical Standardization Programs (CDC CSP) has developed an accurate, high throughput method using ED coupled with isotope dilution ultra-high-performance liquid chromatography tandem mass spectrometry (ED-UHPLC-MS/MS). The ED step uses an internationally recognized procedure and is performed in a custom designed dialyzer system that allows maintaining equal ratio of sample-to-buffer volume. The method uses certified pure primary reference material (National Measurement Institute-M914) as calibrator. The method has a limit of detection of 0.6 pg/mL, with an accuracy of ±5%, and precision less than 10% CV. The measurement range is 2 – 2000 pg/mL. The analytical performance of this method as well as other FT methods used in patient care was assessed using single-donor serum samples. The evaluated methods included two commercially available platforms utilizing Chemiluminescence Immunoassay or radioimmunoassay techniques, as well as six laboratory-developed assays using ED-LC-MS/MS. The results of the interlaboratory comparison study will help assessing the current level of agreement among FT assays, to identify potential factors causing differences among assays, and to assist with developing materials to improve the agreement among assays. Presentation: 6/1/2024