Calcium to Creatinine Ratio Calculator
Calculate urine calcium-to-creatinine clearance ratio (CCCR) to differentiate Familial Hypocalciuric Hypercalcemia (FHH) from Primary Hyperparathyroidism (PHPT).
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Common Searches & Natural Queries
What is the Calcium / Creatinine?
Differentiating between primary hyperparathyroidism (PHPT) and benign familial hypocalciuric hypercalcemia (FHH) is vital to avoid unnecessary parathyroidectomy surgeries. FHH patients harbor inactivating CASR mutations causing the kidneys to abnormally retain calcium.
Mathematical Formula & Methodology
The mathematical model underlying this tool operates on the following verified equation:
CCCR = [Urine Ca (mg/dL) × Serum Cr (mg/dL)] / [Serum Ca (mg/dL) × Urine Cr (mg/dL)]
Understanding the Parameters:
- Urine Calcium (measured in mg/dL) — Primary input variable.
- Serum Creatinine (measured in mg/dL) — Primary input variable.
- Serum Calcium (measured in mg/dL) — Primary input variable.
- Urine Creatinine (measured in mg/dL) — Primary input variable.
How to Use This Calculator
Input synchronous measurements of spot or 24-hour urine calcium, serum creatinine, total serum calcium, and urine creatinine using identical unit systems (mg/dL).
Worked Numerical Example
Urine Ca = 5.2, Serum Cr = 0.9, Serum Ca = 10.8, Urine Cr = 45.0. CCCR = (5.2 × 0.9) / (10.8 × 45.0) = 4.68 / 486.0 = 0.0096. A CCCR < 0.01 strongly supports Familial Hypocalciuric Hypercalcemia (FHH).
Key Considerations & Standards
Diagnostic Thresholds: CCCR < 0.01 suggests FHH (90% sensitivity). CCCR > 0.02 strongly suggests Primary Hyperparathyroidism. Ratios between 0.01 and 0.02 are intermediate and require genetic testing.
Frequently Asked Questions
Why is this distinction so critical for surgeons?
Parathyroidectomy cures primary hyperparathyroidism but fails to normalize calcium in FHH because the genetic defect resides throughout renal tubular calcium sensors.
What if the patient is taking thiazide diuretics?
Thiazides reduce urinary calcium excretion and must be discontinued for several weeks prior to urine calcium assessment to prevent false-low clearance values.