B-127 An Automated Approach to Obtain Delta Check Limits
Authors: kampfrath T , Roach S 
Published: September 2023

Abstract
Delta checking as a systematic approach to quality control specimens was first described by Nosanchuk and Gottmann in 1974. The purpose is to detect specimen errors due to short-sample aspiration, mislabeled cup or sample, incorrect patient draw, problems in analysis, and/or clerical errors. Once inaccuracy is detected, rejection and specimen recollection are the most suitable approach. The delta check procedure compares a patient’s current test results to the previous test results from the same individual using a specified time interval and delta check limit (DCL). The DCL can be expressed as absolute change, percentage change, rate of change, or rate of percentage change. This procedure is typically applied to several analytes, comparing the absolute change with a specified DCL. DCLs are commonly derived from the literature and may be optimized over time based on local patient populations. Creating and modifying DCLs poses a problem, because changes in the DCL can result in flagging too little or too many specimens, and often DCLs don’t take into consideration patient location and therefore lack specificity. Here, we describe a software tool that allows the determination of DCLs based on the individual laboratory’s or ordering unit’s patient results derived from the LIS. The software functionality was tested on a patient dataset from a large county hospital in California, USA. The software allows import of patient data for analysis and creation of population-specific DCLs. Typically, inpatient data is used, as consecutive data points within a common delta check timeframe (hours to days) are less expected for outpatients. The tool allows selection of an unlimited number of analytes of interest to be included in the DCL assessment. Furthermore, the underlying DCL timeframe that compares the two different results is customizable. Lastly, the tool provides the expected number of DCL flags based on the chosen cutoffs. This allows for proper resource allocation or adjustment of the DCL according to available resources. After the import of raw LIS data, an automatic data cleanup is performed. Then the assays of interest and, if available, the associated patient location are directly selected in the software. The dashboard provides each assay test code that is part of the delta checking process, the desired DCL, and the chosen delta check time period (either in hours or days). The resulting expected number of DCL flags is provided specifically for each test, per hour and per day. Any change to the DCL is displayed on the dashboard in real time. Delta checks are a tool to detect specimen inaccuracies resulting from pre-analytical or analytical errors. This software tool provides customized DCLs based on patient population and the individual laboratory instead of deriving them from the literature. This novel customization enables simple derivation of DCLs that are patient population-specific and optimized for each laboratory’s resources. This allows for improved detection of specimen inaccuracies and ultimately leads to improved patient care. *The product is currently under development. Its future availability cannot be guaranteed. Please contact your local Siemens Healthineers organization for further details.