Parathyroid hormone assay. Unreliable and overused.

The records of 100 patients operated on for primary hyperparathyroidism, from Jan 21, 1982 to June 11, 1984, were reviewed. In each patient, hypercalcemia had been documented on at least two separate occasions. A history, physical examination, chest roentgenogram, complete blood cell count with differential, 18-factor automated blood chemistry analysis, and urinalysis were used to screen for other causes of hypercalcemia. Of the 100 patients who had surgery, 88 had a preoperative parathyroid hormone level determination. Preoperative parathyroid hormone levels were normal in 41% of patients with parathyroid disease demonstrated at surgery. Parathyroid hormone assays produce variable results even from the best laboratories. A serum calcium determination remains the best test for diagnosing primary hyperparathyroidism.