Ann Lab Med.  2021 Jan;41(1):51-59. 10.3343/alm.2021.41.1.51.

Moving Rate of Positive Patient Results as a Quality Control Tool for High-Sensitivity Cardiac Troponin T Assays

Affiliations
  • 1Department of Laboratory Medicine, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou, China
  • 2Department of Laboratory Medicine, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China

Abstract

Background
A small shift in high-sensitivity cardiac troponin T (hs-cTnT) assays can lead to different result interpretation and consequent patient management. We explored whether a small bias could be detected using conventional internal quality control (QC) procedures, evaluated the performance of moving average (MA)-based QC procedures, and proposed a new QC procedure based on the moving rate (MR) of positive patient results of hs-cTnT assays.
Methods
The ability of conventional QC to detect a 5 ng/L bias was examined using the 1 3s/ 22s/R4s multi-rule procedure as deviation rules.We developed MA and MR procedures for the hs-cTnT assay using eight months of patient data. The performance of different MA or MR procedures was investigated by calculating the median number of patient samples affected until a bias introduced into the dataset was detected (MNPed). After comparing the MNPed across different procedures, we selected an optimal MA or MR procedure for validation. Validation graphs were plotted using the minimum, median, and maximum number of results affected until bias detection.
Results
Our conventional QC procedures could not detect a positive bias of 5 ng/L. When a positive bias was introduced, MNPed was much higher using MA than using MR, with cut-off values of 5 ng/L and 14 ng/L, respectively. MR validation charts for optimal procedures provided insight into the MR performance.
Conclusions
The MR procedure could detect different errors with few false alarms. In the hs-cTnT assay, the MR procedure with a smaller cut-off value outperformed MA and conventional QC procedures for small bias detection.

Keyword

Internal quality control; Positive bias; High-sensitivity troponin T; Moving average; Moving rate

Figure

  • Fig. 1 Bias detection curves for hs-cTnT MA and MR procedures. Median number of patient samples affected until error detection (MNPed) needed for bias detection using (A) MA procedure, (B) MR procedure with a cut-off value of 5 ng/L, (C) MR procedure with a cut-off value of 14 ng/L, and (D) MR procedure with a cut-off value of 52 ng/L. For the MA curves, 3 and 150 ng/L were used as lower and upper truncation limits, respectively. Numbers in the keys within each panel represent the applied block size for the MA or MR calculation. The dashed line represents the average daily run size of 180 patient results. Abbreviations: hs-cTnT, high-sensitivity cardiac troponin T; MA, moving average; MR, moving rate.

  • Fig. 2 Graphical illustration of how MR QC procedure detects a systematic error. The horizontal green line in the middle of the graph represents the mean of the MR of positive patient results (negative results=hs-cTnT below 5 ng/L; positive results=hs-cTnT above 5 ng/L). The horizontal red lines represent the upper or lower control limits. Abbreviations: hs-cTnT, high-sensitivity cardiac troponin T; MR, moving rate. QC, quality control.

  • Fig. 3 Validation charts for selected optimal patient-based QC procedures for the hs-cTnT assay. (A) MA procedure,(B) MR procedure with a cut-off value of 5 ng/L, (C) MR procedure with a cut-off value of 14 ng/L, and (D) MR procedure with a cut-off value of 52 ng/L. The graphs show the median number of assay results needed for bias detection (MNPed) as bars, and the minimum/maximum number of results needed for bias detection as error bars. The introduced bias is plotted on the X-axis and the MNPed on the Y-axis. Graphs in panels A–C used block sizes of 100, and those in D used a block size of 200. The lower and upper truncation limits for MA procedure are 3 and 150 ng/L, respectively. The dashed line represents the average daily run size of 180 patient results. Abbreviations: hs-cTnT, high-sensitivity cardiac troponin T; MA, moving average; MR, moving rate; QC, quality control.


Cited by  1 articles

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Sunyoung Ahn, Hyun-Ki Kim, Woochang Lee, Sail Chun, Won-Ki Min
Ann Lab Med. 2022;42(3):331-341.    doi: 10.3343/alm.2022.42.3.331.


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