Calcium-Creatinine Clearance Ratio (CCCR)
Differentiates familial hypocalciuric hypercalcemia (FHH) from primary hyperparathyroidism (PHPT) using 24-hour urine and serum measurements.
Warnings:
- Requires accurate 24-hour urine collection; incorrect collection invalidates results
- Patient must be adequately vitamin D replete for formula accuracy
- Spot urine calcium:creatinine ratio is NOT equivalent and should not be used for FHH diagnosis
- Values between 0.01-0.02 are in a gray zone requiring repeat testing
- FHH is typically benign and does not require surgery; correct diagnosis prevents unnecessary parathyroidectomy
Note: Formula in mmol/L units: CCCR = [Urine Ca (mmol/L) x Serum Cr (umol/L)] / [1000 x Serum Ca (mmol/L) x Urine Cr (mmol/L)]. Ensure normal vitamin D status before testing.
Serum calcium measured in mmol/L (or convert from mg/dL: mg/dL x 0.2495 = mmol/L)
Serum creatinine in umol/L (or convert from mg/dL: mg/dL x 88.4 = umol/L)
24-hour urine calcium concentration in mmol/L
24-hour urine creatinine concentration in mmol/L
References
- Familial Hypocalciuric Hypercalcemia - StatPearls - NCBI Bookshelf / NIH (2024)
- Investigation and Management of Hypercalcaemia - Royal United Hospitals Bath NHS Foundation Trust (2023)