Effect of Collection Methods on Salivary Cortisol
Salivary cortisol is a useful measure of hypothalmic-pituitary axis function, but the effects of collection method, sample volume, and environmental conditions on hormone recovery are poorly described. These potential sources of pre-analytical variation were assessed using spiked pooled saliva and assay by liquid chromatography and tandem mass spectrometry (LC-MS/MS). When saliva was collected onto cotton swabs, hormone recovery was determined primarily by volume recovery, which was in turn determined by sample volume. To ensure adequate cortisol recovery, ≥2 ml of saliva must be absorbed onto swabs. This may be difficult for many children and some adults to achieve. Salivary cortisol is remarkably stable to a range of environmental conditions, including repeated freeze-thaw cycles, storage at room temperature and exposure to sunlight. This study shows that it is preferable to obtain saliva by passive drool without swabs if adequate sample volume (≥2 ml) cannot be achieved, and that saliva samples can be returned by standard post without affecting hormone recovery.