Correcting Salivary Analyte Concentrations

for Saliva Flowrate

Some salivary analytes pass from outside the salivary cells and into saliva more slowly than others. If saliva flow is higher these slower-moving analytes will not be able to keep up with the flow, and their concentrations in saliva will be lower. If a correction for saliva flowrate is not made, there will appear to be variation in the concentration of an analyte from subject-to-subject due to different flowrates. This variation could cause problems in statistical analysis that might make it difficult for the researcher to see a treatment effect or to reveal a biomarker-behavior relationship. The correction method explained here enables the researcher to correct the measured analyte concentrations for flowrate. Salimetrics currently advises using this correction method for SIgA and DHEA-S.

Step 1: Estimate saliva flowrate

  • ¬†Set a volume requirement for the sample (for example, 1.0 mL) and measure the time in seconds (use stopwatch) that it takes your subject to collect the specified volume.
  • ¬†Convert the time measured in seconds to minutes
  • Divide the volume collected by the time in minutes to get the flowrate (mL/min)


1.0 45 0.75 1.33
1.0 60 1.00 1.00
2.5 180 3.00 0.83

Step 2: Correct the measured analyte concentration for flowrate

Multiply the measured concentration by the flowrate to express the results as amount of analyte per unit time.
SIgA 205.60 ug/mL x 1.33 mL/min = 273.45 ug/min
1280.00 ug/mL x 0.83 mL/min = 1062.00 ug/min
DHEA-S 997.02 pg/mL x 0.40 mL/min = 398.81 pg/min
5583.30 pg/mL x 0.198 mL/min = 1105.49 pg/min


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