More on Lot-to-Lot Changes

Abstract

To the Editor: Shifts in patient results due to reagent lot changes are a major issue for laboratories, and their investigation is both time-consuming and expensive. In a recent article, Algeciras-Schimnich et al. (1) point out the effect that reagent lot-to-lot changes over time can have on patient results and how these shifts, if large enough, could lead to misdiagnosis and inappropriate treatment. As was the case in this article, on insulin-like growth factor 1, it is often clinicians who alert the laboratory to changes in patient results. We have had similar experiences for a number of analytes, including creatinine. For this analyte, clinicians monitoring renal transplantation patients have asked whether changes as small as from 1.13 mg/dL (100 μmol/L) to 1.24 mg/dL (110 μmol/L) are real or due to shifts in the assay. In the laboratory, shifts in patient results can be caused by a number of assay system components, but the most likely are reagent …