Lab Med Qual Assur 2021; 43(2): 72-79
Published online June 30, 2021
Copyright © Korean Association of External Quality Assessment Service.
1Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul; 2Department of Laboratory Medicine, Jeonbuk National University Medical School; 3Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea
Correspondence to:Joonhong Park
Department of Laboratory Medicine, Jeonbuk National University Hospital, Jeonbuk National University Medical School, 20 Geonji-ro, Deokjin-gu, Jeonju 54907, Korea
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: The control samples for external quality assessment (EQA) must be highly stable during the EQA process. This study aimed to evaluate the stability of in-house prepared external quality controls for autoimmune disease tests, including anti-nuclear antibody (ANA), anti-double stranded DNA immunoglobulin G antibody (anti-dsDNA), anti-thyroglobulin antibody (anti-Tg), and anti-thyroperoxidase antibody (anti-TPO).
Methods: The in-house prepared external quality controls with two different levels (negative and positive for ANA and anti-dsDNA; low and high for anti-Tg; and anti-TPO) for each autoimmune disease test were prepared and stored at test temperatures of –20℃, 4℃, and room temperature (RT). The levels of each autoimmune disease test were measured at baseline and at 1 week, 2 weeks, 1 month, 3 months, and 6 months. The internal quality controls from the same batch run were also tested during the evaluation period.
Results: The negative and positive controls for ANA were stable for 6 months, regardless of storage temperature. The positive control for anti-dsDNA tended to increase in level at 6 months (P =0.033). The low and high anti-Tg controls tended to decrease in levels at 3 months (P =0.033 and P =0.042, respectively). The low control of anti-TPO decreased in level at RT compared to –20℃ at 1 week (P =0.026) and the high anti-TPO controls tended to decrease in level at 3 months regardless of storage temperature such as –20℃, 4℃, and RT (P =0.041).
Conclusions: The stability of in-house prepared external quality controls was influenced by different storage temperatures and durations. These results indicate that all EQA samples for autoimmune disease tests should be stored at –20℃ or 4℃ and be tested as soon as possible during the EQA process.
Keywords: Stability evaluation, In-house prepared quality controls, External quality assessment, Autoimmune disease tests
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