A statistical method to calculate blood contamination in the measurement of salivary hormones in healthy women
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OBJECTIVES: Previous studies have reported that salivary concentrations of certain hormones correlate with their respective serum levels. However, most of these studies did not control for potential blood contamination in saliva. In the present study we developed a statistical method to test the amount of blood contamination that needs to be avoided in saliva samples for the following hormones: cortisol, estradiol, progesterone, testosterone and oxytocin. DESIGN & METHODS: Saliva and serum samples were collected from 38 healthy, medication-free women (mean age=33.8±7.3yr.; range=19-45). Serum and salivary hormonal levels and the amount of transferrin in saliva samples were determined using enzyme immunoassays. RESULTS: Salivary transferrin levels did not correlate with salivary cortisol or estradiol (up to 3mg/dl), but they were positively correlated with salivary testosterone, progesterone and oxytocin (p<0.05). After controlling for blood contamination, only cortisol (r=0.65, P<0.001) and progesterone levels (r=0.57, P=0.002) displayed a positive correlation between saliva and serum. Our analyses suggest that transferrin levels higher than 0.80, 0.92 and 0.64mg/dl should be avoided for testosterone, progesterone and oxytocin salivary analyses, respectively. CONCLUSIONS: We recommend that salivary transferrin is measured in research involving salivary hormones in order to determine the level of blood contamination that might affect specific hormonal salivary concentrations.
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