Saliva collection using cotton buds with wooden sticks: a note of caution.

The aims of the present study were to investigate whether the cotton-tipped applicators (cotton buds) used to collect saliva in infants can be stored un-centrifuged prior to cortisol analysis, and to test whether there is any difference in results between wooden and plastic-shafted sticks. Saliva was collected from 10 healthy adults using 6 cotton buds, i.e. 3 with wooden sticks and 3 with plastic sticks. The samples were then centrifuged at three different time-points: immediately after collection, after 24 h and after 48 h. Using cotton buds with wooden sticks, median salivary cortisol was significantly lower after 24 h (40 %) (p<0.001) and after 48 h (49 %) (p<0.001) of storage than it was of the samples centrifuged immediately. There was no significant difference between the samples centrifuged immediately and those centrifuged after 24 h and 48 h when saliva was collected using the cotton buds with plastic sticks. It is concluded that cotton buds with wooden sticks should not be used in studies of salivary cortisol unless it is possible to centrifuge the saliva immediately. Moreover, it is inadvisable to alternate between cotton buds with wooden and plastic sticks in the same study when collecting saliva for analysis of cortisol.