A critical evaluation of salivary testosterone as a method for the assessment of serum testosterone

Although salivary testosterone (T) is often used in clinical studies accuracy is mostly questionable. State of the art data for men is sparse and for women absent. Our objective was to perform a critical evaluation of salivary T (Sal-T) as a method for indirect assessment of serum T using state of the art methods. Saliva was collected via 'Salivette' and 'passive drooling' methods. Sal-T and free T in serum after equilibrium dialysis were measured by LC-MS/MS RESULTS: Evaluation of Sal-T results versus free T by equilibrium dialysis (ED-T) for men gave: 'Salivette' Sal-T=0.05+0.88x ED-T, r=0.43; 'passive drooling' Sal-T=0.17+0.91x ED-T r=0.71. In women, correlation was comparable but values are higher than free T: 'passive drooling' Sal-T=0.12+2.32x ED-T, r=0.70. The higher than expected T values in saliva, appear to be explained by T binding to salivary proteins. Iso-electric focusing of saliva proteins, followed by fractionation and LC-MS/MS assay of T showed marked testosterone peaks at pH 5.3 and 8.4, providing evidence for T binding in saliva to proteins such as albumin and proline rich protein (PRP).

Passive drooling is the collection method of choice for testosterone in saliva. Sal-T is not directly comparable to serum free T due to T binding to saliva proteins, which substantially affects the low Sal-T in women but not the higher Sal-T in healthy adult men.