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Many hospitals also offer this urine calcium ; creatinine ratio on a spot urine (preferably pre-prandial) which is meant for the investigation of stone disease and haematuria in children, but of NO utility in the diagnosis of FHH.

Interpretation

To exclude Familial Hypocalciuric Hypercalcaemia (FHH), Ca : Cr clearance ratio should be > 0.02. Many authors suggest that FHH is excluded if the ratio > 0.01, but there is a grey area between 0.01 and 0.02

Formula for your information
Urine Calcium (mmol/l) x [Serum Creatinine (umol/l) / 1000]
Serum Calcium (mmol/l) x Urine Creatinine (mmol/l)


For example

FHH
Urine calcium 1.0 mmol/l                          Ratio = 1.0 x [130/1000]      =   0.0079
Serum creatinine 130 umol/l                                       2.65 x 6.2
Serum calcium 2.65 mmol/l
Urine creatinine 6.2 mmol/l

Primary Hyperparathyroidism
Urine calcium 2.2 mmol/l                          Ratio = 2.2 x [74/1000]      =   0.035
Serum creatinine 74 umol/l                                       3.3 x 1.4
Serum calcium 3.3 mmol/l
Urine creatinine 1.4 mmol/l

It is essential to be adequately replaced with vitamin D for this formula to be accurate. Jayasena etal vitamin D evidence  

Written by Dr. Jaimini Cegla, Karim Meeran and Sabri Meeran