The incidence of duplicate genetic testing

PURPOSE: Duplicate genetic testing (DGT) should give the same results as the initial genetic test. Therefore, DGT is indicated only in the rare instances where the initial results require confirmation. The objective of this study was to determine the incidence of DGT by reviewing TPMT, HFE, and CYP450 2D6 polymorphism testing performed in our institution's laboratories in 2006. A secondary objective was to determine the savings in charges that resulted from a system in place to limit HFE DGT. METHODS: A retrospective records review at an academic medical center. RESULTS: The percentage of patients having the same genetic test more than once in 2006 was 3.3% (253/7710) for TPMT, 0.3% for HFE (24/7851), and 0.9% (4/433) for CYP450 2D6 testing. Retail laboratory charges for the DGT identified in 2006 were $76,728. To estimate the incidence of DGT over a longer period of time than 2006, an all-time records review was performed on a subset of internal patients and found the all-time incidence of DGT for TPMT, HFE, and CYP450 2D6 testing to be 6.9%, 1.9%, and 0.9%, respectively. No case of DGT with an appropriate indication for duplicate testing was found. A system in place to decrease HFE DGT is estimated to have saved $77,479 in charges for 2006 (95% CI, $35,512-184,015). CONCLUSIONS: Indicated DGT is rare and decreasing DGT could result in significant savings. Institutions should consider implementing a systems-based process to limit DGT.