Correcting SIgA Concentrations for Saliva Flowrate

(SOS Collection)

Some salivary analytes such as SIgA pass from outside the salivary cells into saliva more slowly than others. If saliva flow is higher the SIgA will not be able to keep up with the flow, and its concentration in saliva will be lower. If a correction for saliva flowrate is not made, there will appear to be variation in the concentration of SIgA 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 SIgA concentrations for flowrate when using the SOS collection device.

Step 1: Estimate saliva flowrate

• Measure the weight (in grams) of the saliva storage tube (SST) and Salimetrics Oral Swab (SOS).

• Set a time requirement for the saliva collection. If possible, use a stopwatch to measure the time that the swab is in the subject’s mouth.

Note: The swab should be removed from the mouth before reaching saturation (maximum volume = approximately 2.0 mL), since after that point no further sample is collected, and the calculation of the flow rate would be affected. Normally, 1 minute should be adequate, but dehydrated subjects may require extra collection time. A pilot study may be necessary

• After collection, return the swab (SOS) into the tube (SST) and weigh both again. The difference from the initial (dry) weight will approximately equal the saliva volume in milliliters (mL).

• Divide the volume collected by the time used for collection to get the flow rate (mL/min).

Examples: 1.5 mL ÷ 1.0 min = 1.5 mL/min
1.5 mL ÷ 5.0 min = 0.3 mL/min

Step 2: Correct the measured SIgA concentration for flowrate

Multiply the measured concentration by the flowrate to express the results as amount of SIgA per unit time.

Examples: 205.6 ug/mL x 1.5 mL/min = 308.4 ug/min
1280.0 ug/mL x 0.3 mL/min = 384.0 ug/min