Please select the eligibility criteria that correspond to the clinical trial below.
Title: Assessment of the Relationship Between Salivary Phosphorus and Level of Kidney Function
Brief Summary: The specific purpose of this study is to describe the relationship between salivary phosphorus and kidney function, specifically as it relates to serum phosphorus, FGF23, PTH, vitamin D status and urinary excretion of phosphorus.


Options:
A: Inclusion Criteria:

1. Patients with a GFR of \< 45 ml/min;
2. Intact serum PTH \> 37 pg/ml;
3. Age \> 35 years (both genders and all races);
4. Able to perform two three-week balance studies;
5. Not on oral calcium or vitamin D other than multi vitamin, or willing to stop calcium or vitamin D for one month prior to entry in the study (day 1 of first calcium balance period);
6. Female patients must be post-menopausal (defined as last menstrual period at least 12 months prior to screening visit) or surgically sterile by hysterectomy;
7. On stable doses of diuretics, bisphosphonates, anti-epileptics (except dilantin) for at least 2 months.

Exclusion Criteria:

1. Serious underlying systemic disease (including uncontrolled diabetes, lupus, hypertension, amyloid, etc);
2. Taking drugs that alter calcium and phosphate balance or homeostasis including high dose cholecalciferol or ergocalciferol (1000 U/day or 50,000U/ wk, respectively), active vitamin D metabolites, calcimimetics, PTH analogues in the last 30 days;
3. Taking drugs that the investigator feels will alter calcium balance;
4. Plan to initiate dialysis in the next six months;
5. Hypercalcemia defined as serum calcium \> 10.5 mg/dl;
6. Hyperphosphatemia defined as serum phosphate \>5.5mg/ml;
7. Intestinal disease that alters absorption or normal intestinal function including celiac disease, small bowel resection, bariatric surgery;
8. Smoking
B: Inclusion Criteria:

* age \>18 years
* eGFR 20-45 by modified MDRD equation
* protein/creatinine ratio \<5
* blood pressure \<150/95
* not taking calcium binder or supplements, vitamin D, or phosphate binders
* normal serum phosphorus and calcium corrected for albumin and intact PTH \<100pg/ml
* medically stable
* able to give informed consent and come for all visits

Exclusion Criteria:

* history of significant liver disease or cirrhosis
* medically unstable
* unable to tolerate diets
C: Inclusion Criteria:

* Men or women greater than 18 years of age.
* The subject has voluntarily signed and dated the most recent informed consent form approved by an Institutional Review Board (IRB).

Exclusion Criteria:

* Receiving hemodialysis.
* Receiving or has received an investigational product (or is currently using an investigational device) within 28 days prior to Visit 2.
* Evidence of active and clinically significant infection at Visit 2.
* Dental work within 48 hours prior to Visit 2.
D: Inclusion Criteria:

* Age \> 18 years
* Capable of giving informed consent
* Duration of peritoneal dialysis \> 3 months
* Dose of phosphate binder(s) stable over previous 2 week period
* Plasma phosphours \> 4.9 mg/dL based on most recent laboratory data within 1 month of enrollment

Exclusion Criteria:

* Pregnancy
* Known liver disease
* Active peptic ulcer disease
* Treatment with carbamazepine
* Intolerance to niacinamide or niacin
* Current medication regimen including niacin or niacinamide \> 100 mg daily
* Planned or expected surgical procedure in the next 4 months
* Patients in nursing home or extended care facilities where administration of the study drug may not be appropriately given

Answer: C