Delta checks were first described in 1974 by Nosanchuk and Gottmann as a means to improve QC in clinical laboratories (1). Traditionally, delta checks have been defined as the difference between a current result and a previous result that occurs within a set time period, with establishment of limits for each individual analyte. Delta checks that exceed established limits are held for manual review by laboratory technicians, which may include assessing for specimen mix-up; checking QC data and instrumentation; examining specimen quality, volume, and integrity; specimen reanalysis; and/or review of the patient's medical record to determine whether the change is explained by clinical status. Additionally, delta checks can …