Expert Access - The Delta Check in Action: Causes and Consequences of Discrepant Laboratory Results

Eugenio Zabaleta

Joely Straseski, PhD, MS, MT(ASCP), DABCC

March 15, 2011




The Delta Check in Action

You check a patient’s sodium on Monday and it is 145 mEq/L.  You check it 4 weeks later and it is now 154 mEg/L.  What caused that change?  Is the patient ill?  Is this a normal fluctuation over time?  Is the patient on corticosteroids?  Or was the patient simply dehydrated?  All are viable explanations for the discrepancy observed between these laboratory values.

Discrepant results are often identified by delta check alerts.  Delta checks compare current laboratory results to previous results; if the difference between the two values exceeds predetermined biological limits (within a predetermine length of time), a technologist is alerted and the discrepancy can be investigated further.  Causes of discrepant laboratory results include both preanalytical and analytical issues, and true biological changes occurring within the patient.

Among the preanalytical causes of discrepancies are sample integrity issues and possible misidentification of a patient or specimen.  Importantly, these types of issues cannot be detected by traditional QC methods.  Both of these situations may lead to erroneous laboratory results, compromising patient care by leading to inappropriate diagnoses or treatment.  Delta check alerts provide an additional means to identify these types of problems, in addition to alerting health care providers to true changes in their patient’s condition. 

This presentation highlights current methods used to determine delta check limits, tips for implementing a systematic investigation of discrepancies, and clinical implications of reporting discrepant results.



Dr. Straseski is Medical Director of endocrinology at ARUP and Assistant Professor of pathology at the University of Utah’s School of Medicine.  She began her laboratory career as an ASCP board certified Medical Technologist, then went on to earn a Master’s degree in bacteriology and a PhD in pathology and laboratory medicine from the University of Wisconsin-Madison, where she also served as a postdoctoral associate in the Department of Pathology.  Dr. Straseski completed her postdoctoral fellowship in clinical chemistry at the Johns Hopkins Medical Institutions in Baltimore, Md.  She has previously been awarded the Past-President Scholarship by the American Association for Clinical Chemistry, as well as a Distinguished Abstract Award from the National Academy of Clinical Biochemistry.  Dr. Straseski is a diplomate of the American Board of Clinical Chemistry.

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