Salivary Phosphorus and Level of Kidney Function

Previous studies have demonstrated that salivary phosphate levels are elevated in patients
with chronic kidney disease and that there is a direct and linear correlation between serum
phosphorus and salivary phosphorus. However, data regarding the relationship between
salivary phosphate levels and stage of kidney disease (estimated glomerular filtration rate
(eGFR) is lacking; as such, this study seeks to examine that relationship.

There is a normal circadian rhythm to serum phosphorus with a mid-afternoon peak at
approximately 3 PM and a nadir at approximately 7-11 AM. Furthermore it has been
demonstrated that a fasting serum phosphorus level at 8 AM is NOT indicative of 24 hour mean
serum phosphorus. Thus the relationship between salivary phosphorous and serum phosphorus
may vary over the course of the day.

This is a single-center study in which saliva, urine, and serum will be collected at two
time points in a minimum of 105 subjects with various degrees of renal function (not on
dialysis). Assignment to the renal group will be based upon the Visit 2 estimated
glomerular filtration rate value. Enrollment in each group will continue at random until
the target of 15 subjects per group is achieved. It is possible that an individual group may
exceed the target enrollment number as their assignment will occur retrospectively.

All subjects will be required to have their morning assessment conducted between the hours
of 7AM and 11AM. Clinical chemistry, serum phosphorus, intact parathyroid hormone(iPTH),
plasma fibroblast growth factor 23 (FGF-23),serum 1,25 di-hydroxyvitamin D, serum 25-OH
vitamin D, and a spot urine will be collected. A 24-hour urine sample will also be
collected.

Passive and stimulated salivary collection will occur. The salivary collection must occur in
a fasting state with nothing to eat or drink for at least 90 minutes prior to the
collection.

Subjects will be permitted to leave the facility. They will be instructed to consume a
lunch of their choice between the hours of 1100AM and 1200PM. They will be instructed to
eat nothing after 1200PM. Subjects will return to the clinic for Visit 3 as directed by
the study staff. Visit 3 will be conducted between 1PM and 4PM. Laboratory assessments,
salivary collections, and spot urines will be collected at Visit 3. A dietary recall of
intake at Visit 2 and 3 will also be completed.