Validation of a Dried Blood Spot Assay for Testosterone Measurement Using Liquid Chromatography-Tandem Mass Spectrometry.

Testosterone is a critical hormone involved in regulating various physiological processes in both men and women. Accurate testosterone measurement is essential for diagnosing endocrine disorders such as hypogonadism and polycystic ovary syndrome and for routine testing. Traditionally, testosterone levels are measured using serum or plasma samples, which present challenges in sample collection, storage, and transport, particularly in resource-limited settings. Dried blood spot (DBS) sampling has emerged as an effective alternative for hormone analysis, offering significant advantages in terms of sample stability, ease of collection, and simplified logistics. This study aimed to validate a DBS-based testosterone assay using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to ensure accuracy and precision comparable to conventional serum-based methods. Drops of whole blood samples were collected from adult volunteers using a single-use safety lancet for finger pricks, with blood applied onto DBS cards (PerkinElmer 226 Spot Saver RUO card) for further analysis. The testosterone was extracted from DBS using a liquid-liquid method and analyzed with LC-MS/MS. The assay demonstrated excellent linearity across a wide concentration range (0.1-100 ng/mL) with a correlation coefficient (r) of 0.999 and achieved a lower limit of detection of 0.058 ng/mL and a lower limit of quantification of 0.086 ng/mL. The method showed high precision, with intra- and inter-day coefficients of variation below 10%, and satisfactory recovery rates. Hematocrit correction and matrix effect evaluations confirmed the robustness of the assay for clinical and research applications. Additionally, the assay displayed a strong clinical correlation between testosterone levels in DBS and venous serum samples, supporting its reliability for testosterone monitoring. This validation study supports that the DBS-based LC-MS/MS testosterone assay is a reliable tool for testosterone quantification for routine testing.