J Lab Med Qual Assur.  2020 Sep;42(3):121-129. 10.15263/jlmqa.2020.42.3.121.

Usefulness of Reference Change Values for Delta Check Limits in Clinical Laboratory Testing

Affiliations
  • 1Department of Laboratory Medicine, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Incheon, Korea
  • 2Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 3Department of Laboratory Medicine, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 4Department of Laboratory Medicine, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea

Abstract

Background
In this study, the usefulness of within-subject biological coefficient of variation (CVI) and reference change values (RCVs) for delta check limits were investigated by comparing the population distributionbased delta check limits.
Methods
For six tests, including aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, glucose, creatinine, and hemoglobin, the RCV95%, RCV99%, and RCV99.9% delta limits were obtained. The nonparametric 95% and 99% delta limits were obtained from the population distribution of the delta percentage difference of the health examination group (January 2014 to December 2018) and the outpatient and inpatient groups (January to December 2018). Delta check alerts (%) in total and all three subgroups were examined according to the five different delta check limits. Additionally, we analyzed the correlation of the median CVIF estimates with population-delta check limits for the six tests.
Results
The delta percentage difference of the six tests showed a nonnormal distribution, and median value significantly differed among the health examination, outpatient, and inpatient groups (all, P <0.001). The overall delta check alerts of six tests decreased in the order of RCV95%, RCV99%, and RCV99.9%, population distribution -95%, and -99% delta limits; the proportion of the health examination group gradually decreased and that of inpatients increased. A good correlation was observed between median CVI (range, 2.7% to 10.1%) and population distribution delta limits (r =0.96 to 0.99).
Conclusions
The RCV delta check limits should be applied differently depending on the health and disease group. CVI can be useful for estimating the delta check limits of the population.

Keyword

Reference change value; Delta check limits; Quality control; Biological variation
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