Measurement of hormone levels by salivary testing is currently in vogue, yet for now, the enthusiasm to embrace this approach far exceeds its capacity to reliably achieve precise and accurate estimates of testosterone at low levels. In this issue of Menopause, Flyckt et al,(1) directly compare measurement of testosterone levels in postmenopausal women using salivary versus serum testing. In doing so, they open a virtual Pandora’s box of issues surrounding measurement of testosterone in general and particularly at low levels, such as those seen in women and children.
Salivary testing of hormones is a valid approach, effectively representing an ultrafiltrate of blood, and has the benefits of being less invasive and potentially less expensive than the serum approach. Salivary cortisol, for example, has been described as having high diagnostic accuracy for the screening of Cushing syndrome and has been recommended in clinical practice guidelines for screening for this condition.(2)
However, as Flyckt et al report, the current technology is such that the accuracy of
testosterone levels achieved by the salivary method is questionable in individuals whose actual testosterone levels are low.
The authors directly compare salivary versus serum testosterone levels in 56 postmenopausal women who provided multiple samples for hormone analysis both before and during treatment with a 300-Kg transdermal testosterone patch versus placebo.
Direct correlation between the methods was poor, although improved somewhat after log transformation of non-normally distributed data. The authors concede that the very low levels of testosterone in their study sample of postmenopausal women were likely to provide a challenge for the salivary approach to measurement. The other issue is that different immunoassays were used to compare testosterone levels as collected by salivary versus the serum approach; others have reported the variation between results from testosterone immunoassays to be broad.(3) The most concerning aspect of the findings from this