Dried blood spot sampling of testosterone microdosing in healthy females

Capillary dried blood spot (DBS) analysis coupled with multi-analyte steroid liquid chromatography mass spectrometry (LCMS) is attractive for field studies, home-based self-sampling as well as clinical trials by eliminating costly and laborious sample processing involving venipuncture and frozen storage/shipping while providing multiple steroid measurements from a single small sample. We investigated steroid measurements in DBS samples stored for four years at room temperature prior to analysis compared with the original venipuncture serum samples. Healthy women (n=12) provided paired DBS and blood samples over two weeks run-in before seven days treatment with daily transdermal T gel (12.5 mg) and after the end of treatment on days 0, 1, 2, 4, 7 and 14. Compliance with treatment and sampling was high and no adverse effects were reported. Testosterone (T), androstenedione (A₄), 17 hydroxyprogesterone (17OHP) and progesterone (P₄) were measured in extracted DBS samples as whole blood concentrations with and without adjustment for hematocrit. Using the same LCMS methods, DBS T and A₄ measurements had high correlation with minimal bias from prior serum measurements with DBS T displaying the same pattern as serum, with or without hematocrit adjustment. However, serial whole blood measurements of T without hematocrit adjustment provided the best fitting model compared with serum, urine, or hematocrit-adjusted whole blood T measurements. These finding facilitate and simplify DBS methodology for wider field and home-based self-sampling studies of reproductive steroids indicating the need for hematocrit adjustment may be superfluous.