Analysis of patient results distributions to reevaluate a reference range change for calcium, after a change in assay reagents on the Roche Cobas c500 analyzer

Upasana Joneja, Thomas Jefferson University Hospital
Laura J. McCloskey, Thomas Jefferson University Hospitals, Philadelphia, PA
Douglas F. Stickle, Thomas Jefferson University Hospitals, Philadelphia, PA

Document Type Poster

Presented at ASCP in Tampa Florida.



A change in reagents for calcium (Ca) on the Roche Cobas c500 used in our laboratory analyzer took place in 2013. The previous reference range (8.5-10.5 mg/dL) was replaced with that from the manufacturer's study (8.6-10.0 mg/dL), based on correlation of results between the new and old assays. As a matter of quality assurance, we undertook a post-assay-change reevaluation of the reference range change, using a method based on that of Bhattacharya [1]. In short, the method relies on the assumption that the reference range is a normal distribution, which assumption enables this distribution to be isolated mathematically from within all-comers patient distribution data that are not normally distributed.