The Chloride-Phosphate Ratio in Hypercalcemia

Serum chloride and phosphate concentrations were measured in 52 hypercalcemic patients. The chloride values were higher (mean, 107 meq/litre) and phosphate, lower (mean, 2.6 mg/100 ml) in the 25 hyperparathyroid patients, whereas the chloride concentrations were lower (mean, 98 meq/litre) and phosphate, higher (mean, 4.5 mg/100 ml) in the 27 patients with hypercalcemia from other causes. The chloride-to-phosphate ratio ranged from 31.8 to 80 in hyperparathyroidism, with 96% more than 33, and from 17.1 to 32.3 in those with hypercalcemia from other causes, with 92% less than 30. The chloride-to-phosphate ratio differentiated well between these two groups of hypercalcemic patients.