Reliability of Serum Calcium to Phosphorus (Ca/P) Ratio as an Accurate and Inexpensive Tool to Define Disorders of Ca-P Metabolism

Study Overview
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Brief Summary
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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.

Official Title
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Serum Calcium to Phosphorus (Ca/P) Ratio to Define Disorders of Ca-P Metabolism

Conditions
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Phosphorus and Calcium Disorders

Intervention / Treatment
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* Other: No intervention are provided


Participation Criteria
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Eligibility Criteria
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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.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 90 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| First study group: patients with PHPT<br>Patients aged between 18-90 years old with primary hyperparathyroidism who had been diagnosed in the Unit of Endocrinology of the University of Modena and Reggio Emilia. 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. | Other: No intervention are provided<br> <br> |
| Second study group: patients with HypoP<br>Subjects with reduced serum P, but normal serum Ca, will be enrolled among HIV-infected patients on HAART treatment from the Modena cohort. 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. | Other: No intervention are provided<br> <br> |
| Control group<br>Patients that underwent biochemical examination by primary care physician or by endocrinologist in order to assess their calcium-phosphorus metabolism state with normal results. 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. | Other: No intervention are provided<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum Calcium to Phosphorus ratio | Calculated formula (serum calcium to serum phosphorus ratio) | Assessed only once at the diagnosis (from January 2005 to January 2018) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum Calcium | From blood sample - Unit of measurement: mg/dl | Assessed only once at the diagnosis (from January 2005 to January 2018) | 
| Serum Phosphorus | From blood sample - Unit of measurement: mg/dl | Assessed only once at the diagnosis (from January 2005 to January 2018) | 
| Serum Parathormone | From blood sample - Unit of measurement: pg/ml | Assessed only once at the diagnosis (from January 2005 to January 2018) |