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The Performance of the Agility System for Interferon Gamma Release Assay Using QuantiFERON TB Gold In-Tube Assay
J Lab Med Qual Assur 2019;41:29-38
Published online March 31, 2019
© 2019 Korean Association of External Quality Assessment Service.

Kwanghyuk Seok and Soyoun Shin

Laboratory Medicine Center, The Korean Institute of Tuberculosis, Cheongju, Korea
Correspondence to: Soyoun Shin, Laboratory Medicine Center, The Korean Institute of Tuberculosis, 168-5 Osongsaengmyeong 4-ro, Osong-eup, Heungdeok-gu, Cheongju 28158, Korea Tel: +82-43-249-4940 Fax: +82-43-249-4954 E-mail: leukoso@naver.com
Received August 21, 2018; Revised December 3, 2018; Accepted December 13, 2018.
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.
 Abstract
Background: As stated in 쁔he Action Strategy for Tuberculosis-Free Korea, last March, high-throughput, large-scale analytical instruments for interferon gamma release assays (IGRA) are demanded by many clinical laboratories using the QuantiFERON-TB Gold In-Tube assay (Cellestis/Qiagen, Australia). Agility (Dynex Technologies, USA) is an automated high-throughput enzyme linked immunosorbent assay analyser. The present study aimed to evaluate its accuracy and speed.
Methods: Pooled plasma was prepared using samples obtained after IGRA testing. Analyses of precision, linearity, cut-off evaluation, and comparison with conventional methods were performed for multiple Agility instruments according to the Clinical and Laboratory Standards Institute EP5-A3, EP6-A, EP9-A3 and EP12-A2 guidelines. The turnaround time and throughput were also analysed.
Results: The coefficient of variation range was 2.48%4.0%, 7.01%11.17%, and 9.69%14.84% for the repeatability, between-run precision, and between-day precision analyses, respectively. The linearity ranged from 0 to 10.541. Comparison analysis presented a high concordance of Agility with the conventional instrument, DS2 (Dynex Technologies), and manual method for IGRA. The cut-off value of 0.35 IU/mL was well compatible with the C50. It was identified that the C50짹20% contained the C595 interval. The average turnaround time was 3.84 hours, from the submission of pre-treated samples to the reporting of results. The throughput was determined to be 290 tests during a routine working time of 8 hours.
Conclusions: Agility showed high precision, linearity, concordance, and had a 2.5 times faster throughput than with the conventional and manual method. It could be useful for large-scale IGRA testing in latent tuberculosis infection screening project. Samples within C50짹20% are suspected to show relatively low reporducible results of high inversion between postivie and negative.
Keywords : Agility, Interferon gamma release assays, Latent tuberculosis infection, QuantiFERON-TB Gold In-Tube