MON-123 Underdiagnosis of Primary Hyperparathyroidism in the Outpatient Setting of an Academic Health Care System

Background: Primary hyperparathyroidism (PHPT) is the leading cause of hypercalcemia in the outpatient population and is associated with nephrolithiasis, osteoporosis, and further end-organ effects. When indicated, parathyroidectomy is an effective intervention. The aim of this study was to assess the prevalence of patients with hypercalcemia resulting from undiagnosed PHPT within a large, urban, academic healthcare system. Methods: The study population comprised all patients within UCLA Health. The electronic medical record was queried between 01/01/2016-12/31/2018 to include patients with at least two elevated serum total calcium concentrations (>10.4 mg/dL) within a six-month period in the outpatient setting. Causes of secondary and tertiary PHPT were excluded. In concordance with the PHPT diagnostic criteria outlined by the Fourth International Workshop, we evaluated the proportion of patients with hypercalcemia who were further assessed with a serum intact parathyroid hormone (iPTH) test. The study identified cases of PHPT as defined by confirmed elevated serum total calcium concentrations and elevated or inappropriately normal iPTH concentrations. Results: There were 7102 patients with a single elevated serum total calcium result who never received a repeat assessment within the study period. Although there were 5617 patients with confirmed hypercalcemia, only 2773 (51%) had an iPTH level assessed within six months of the repeated calcium measurement. Of those who underwent iPTH testing, 1931 (69%) were biochemically confirmed to have classic (34.2%) or normohormonal (35.4%) PHPT; the remaining 31% had an appropriately suppressed iPTH concentration relative to the hypercalcemia. Conclusions: In a large, academic, tertiary healthcare center, over half of the ambulatory patients with confirmed hypercalcemia did not receive further work-up to assess for possible PHPT. Efforts to improve diagnosis of PHPT and expand curative treatment have the potential to decrease the prevalence of nephrolithiasis, bone loss, and further end-organ effects associated with the disease.