Sensitivity. The theoretical detection limit, de-
fined as the minimal concentration of testosterone that
can be distinguished from zero, was obtained by interpolating
the mean minus 2 SD for 20 replicates of
the 0 pg/mL testosterone calibrator. By this method
the limit of this assay’s sensitivity is 0.8 pg/mL. To
corroborate this theoretical detection limit, we routinely
include an external control representing 0.7 pg/
mL. Across 19 runs this control reads on average 0.749
pg/mL (SEM 5 0.02).