CHLORIDE PHOSPHATE RATIO AS THE SCREENING-TEST FOR PRIMARY HYPER-PARATHYROIDISM

Serum chloride and phosphate concentrations were measured in 79 hypercalcemic patients. The chloride values were higher (mean 106.7 meq/l) and phosphate lower (mean 2.08 mg/100 ml) in the 53 hyperparathyroid patients, whereas the chloride concentrations were lower (mean 99.3 meq/l) and phosphate higher (mean 4.07 mg/100 ml) in the 26 patients with hypercalcemia from other causes. The chloride phosphate ratio ranged from 19-32 in the subjects with hypercalcemia from other causes with 90% of values less than 30. In patients with primary hyperparathyroidism, 96% of the values were more than 34. This ratio is apparently a very useful and simple preliminary test for distinguishing patients with primary hyperparathyroidism from patients with hypercalcemia from other causes, with normal renal functions.