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)

• Jeong TD
• Cho EJ
• Lee K
• Lee W
• Yun YM
• Chun S
• Song J
• Min WK

• KMID: 2512716
• DOI: http://doi.org/10.3343/alm.2021.41.4.372

Abstract

Background
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.
Methods
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.
Results
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%).
Conclusions
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.

Keyword

Accuracy; Bias; Creatinine; Proficiency testing; Survey

Figure

• 

  Fig. 1 Trend in mean percentage bias in the ABCr PT survey by the KEQAS (2011–2019). N represents the number of participating laboratories in the first (A) and second (B) ABCr PT survey of the year. Abbreviations: ABCr PT, accuracy-based creatinine proficiency testing; KEQAS, Korean Association of External Quality Assessment Service.

• 

  Fig. 2 Mean percentage bias in the ABCr PT survey stratified by (A) Cr concentrations and (B) assay methods. Abbreviations: ABCr PT, accuracy-based creatinine proficiency testing; Cr, creatinine; NT, not tested.

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  Fig. 3 Forest plot of mean percentage bias in the ABCr PT survey stratified by year. (A) Reagent manufacturer group. (B) Instrument manufacturer group. A and B in parenthesis are the number of participating laboratories in the first and second ABCr PT survey of the year, respectively. Abbreviations: ABCr PT, accuracy-based creatinine proficiency testing; CI, confidence interval.

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