A-090 Impact of Changing Total Calcium Methodology on Observed Hypercalcemia Prevalence at an Academic Health System

Abstract Background The UC Davis Health clinical chemistry laboratory implemented a new total automation (Roche Diagnostics, Indianapolis, IN) system in February 2022—replacing prior (Beckman Coulter, Brea, CA) that was place since 2007. In August 2022, primary care and endocrinology providers contacted leadership to report an increase patients with calcium values flagged as abnormally elevated, resulting increased communications from referrals endocrinology. This change testing methodology produced shift the upper reference interval limit 10.5 mg/dL 10.0 mg/dL. determined photometrically vs by indirect potentiometry via outgoing method. We hypothesize photometric-based measurements be more sensitive. Methods conducted retrospective study investigate reported hypercalcemic values—our electronic health system’s (EHR) EPIC’s self-service reporting tool (“SlicerDicer”) utilized for data acquisition visualization. Although had already been verified implementation, “normal study” re-confirm manufacturer derived intervals. One hundred thirty-six samples apparently healthy adults (age ≥ 18 years) were banked this study. Parathyroid hormone (PTH) then measured confirm levels within normal limits. Additional observational also collected PTH pre- post-new line implementation. Quality control (QC) proficiency (PT) reviewed during time. Results four months preceding implementation of line, 1211 compared 5146 similar post time period (302.8/month 1286.5/month), or 324.9%. During these same periods, abnormal observed at 270.8/month pre-implementation 393/month (45.2% increase). An concurrently performed (30.3%; 583.8/month 760.8/month), though greater seen elevated (294.5%; 22.8/month 89.8/month). twenty included study, which mean (SD) value 9.3 (0.33) mg/dL, confirming manufacturer-derived intervals 8.7–10 No biases, shifts, trends PT QC analyzer change. Conclusion Increased events post-automation is likely not due analytical error inappropriate intervals, but rather sensitivity methodology. Hypercalcemic cases our corroborated corresponding values. perceived could known limitations (i.e., lack selectivity, difficulty detecting all forms calcium, etc.). Further investigation warranted determine overall impact changing one assay on system.