Rapid saliva processing techniques for near real-time analysis of salivary steroids and protein

Point-of-care (POC) measurements using saliva samples have immense potential to assess systemic health and wellbeing, but sample viscosity and contaminants can affect analyses. We sought a portable clean-up method for whole saliva appropriate for use with POC measurement techniques such as biosensors.

Whole saliva from each of 13 male subjects was split into 5 fractions. Each fraction was treated with a different clean-up process: a freeze-thaw-centrifuge (FTC) step; centrifugation alone; or passage through a Mini-UniPrep polyethersulfone filter, cotton Salivette, or foam Oracol device. Following clean-up, each subject's treated saliva fractions were assayed for cortisol, testosterone, dehydroepiandrosterone (DHEA), and protein concentrations. The effects of clean-up methods on nonspecific binding (NSB) in a biosensor were also assessed.

Compared with FTC, no analytes were affected by centrifugation alone. Cotton Salivettes significantly altered all analytes, with increases in cortisol (+64%), testosterone (+126%), and DHEA (off-scale) levels, and decreased protein (-21%) and biosensor NSB (-75%). Oracol foam devices decreased DHEA levels by 28%. Mini-UniPrep filtration decreased testosterone (-45%) and DHEA (-66%) concentrations while increasing cortisol (+40%).

No method was optimal for all analytes, highlighting the need for validation of saliva treatment methods before their adoption in rapid POC analyses.