Reliability of Serum Calcium to Phosphorus (Ca/P) Ratio as an Accurate and Inexpensive Tool to Define Disorders of Ca-P Metabolism
Reliability of Serum Calcium to Phosphorus (Ca/P) Ratio as an Accurate and Inexpensive Tool to Define Disorders of Ca-P Metabolism
BACKGROUND: Primary hyperparathyroidism (PHPT) is the third most common endocrine disorder.
 The Ca/P ratio is an accurate tool to differentiate patients with PHPT (>3.5 if Ca and P are
 expressed in mg/dl) from healthy subjects. The reliability of this index is based on the fact
 that serum Ca and P are inversely related together. However, other disorders of the Ca-P
 metabolism, such as hypophosphoremia (HypoP) not related to PHPT, might also impair the Ca/P
 ratio.

 OBJECTIVE: To validate the accuracy of Ca/P ratio in the diagnosis of Ca-P metabolism
 disorders, including also patients with documented HypoP not related to PHPT.

 METHODS: A single-center, retrospective, case-control study will be carried out.

 Biochemical measurements will include parathormone (PTH), vitamin D, serum Ca and P, serum
 albumin and creatinine.
Inclusion Criteria:

 -  patients with diagnosis of primary hyperparathyroidism

 -  HIV-infected patients with reduced phosphorus but normal calcium

 -  subjects with normal Calcium-Phosphorus metabolism

 Exclusion criteria for both cases and controls will be:

 -  age younger than 18 or older than 90 years

 -  severe renal and liver diseases (i.e. glomerular filtration rate (GFR) <30 ml/min)

 -  hyperparathyroidism secondary to Vitamin D deficiency

 -  active metabolic bone disease (e.g. Paget's disease of the bone, osteomalacia,
 rickets, etc)

 -  any type of cancer

 -  malnutrition

 -  severe obesity (BMI > 40 kg/m2)

 -  a history of gastrointestinal malabsorption

 -  sarcoidosis

 -  hypercortisolism

 -  diabetes insipidus

 -  hyperthyroidism

 -  pseudohypoparathyroidism

 -  familial hypocalciuric hypercalcemia (FHH)

 -  treatment with steroids, active forms of vitamin D (calcitriol, ergocalciferol, etc),
 thiazides, phosphate binders, lithium, cinacalcet, bisphosphonates, and denosumab.