Potential Pitfalls of the 2-Hour Calcium-to-Creatinine Ratio and Urinary Cyclic Adenosine Monophosphate Excretion in the Differential Diagnosis of Idiopathic Hypercalciuria

Abstract

Patients (44) with calcium urolithiasis on high (900 mg daily) and low (400 mg daily) Ca diets were studied. With 24 h urinary data, the patients were categorized as normocalciuric or hypercalciuric, and subdivided the hypercalciuric patients into absorptive and renal types. Abbreviated tests, including the 2 h fasting urinary Ca-to-creatinine ratio and 24 h urinary (nephrogenous) CAMP, did not predict accurately whether hypercalciuria was of the idiopathic, absorptive or renal type; 24 h urinary Ca excretions on the low calcium diet had a sensitivity and specificity of > 90% for reproducing the categorized diagnoses.