Ann Lab Med.  2021 Jul;41(4):372-379. 10.3343/alm.2021.41.4.372.

Recent Trends in Creatinine Assays in Korea: LongTerm Accuracy-Based Proficiency Testing Survey Data by the Korean Association of External Quality Assessment Service (2011–2019)

  • 1Department of Laboratory Medicine, Ewha Womans University College of Medicine, Seoul, Korea
  • 2Department of Laboratory Medicine, Hallym University Dongtan Sacred Heart Hospital, Hallym University College of Medicine, Hwaseong, Korea
  • 33 Department of Laboratory Medicine, Seoul National University Bundang Hospital and College of Medicine, Seongnam, Korea
  • 4Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
  • 5Department of Laboratory Medicine, Konkuk University School of Medicine, Konkuk University Medical Center, Seoul, Korea


Accurate serum creatinine (Cr) concentration measurement is essential for evaluating kidney function. In 2011, the Korean Association of External Quality Assessment Service (KEQAS) launched an accuracy-based Cr proficiency testing (ABCr PT) survey. We analyzed long-term data of the KEQAS ABCr PT survey collected between 2011 and 2019 to assess recent trends in Cr assays in Korea.
The ABCr PT survey including three commutable fresh-frozen serum samples was performed twice a year. The target Cr concentration was assigned using isotope-dilution mass spectrometry. We analyzed data obtained from the participating laboratories, calculated the yearly bias, and evaluated bias trends for the major reagents and instruments. Outliers were excluded from all analysis.
The mean percentage bias based on the total data of all participating laboratories was 10.8% in the 2011-A survey and 0.2% in 2019-B survey. Bias for the major reagents and instruments differed depending on the manufacturer. Enzymatic assays generally showed desirable bias ranging from –3.9% to 3.2% at all Cr concentrations and lower interlaboratory variability than non-enzymatic assays (enzymatic vs. non-enzymatic, 3.3%– 7.2% vs. 6.3%–9.1%).
Although the mean percentage bias of Cr assays tends to decrease over time, it is necessary to continuously strive to improve Cr assay accuracy, especially at low concentrations.


Accuracy; Bias; Creatinine; Proficiency testing; Survey
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