Ann Lab Med 2018; 38(5): 420-424  
Proposed Imprecision Quality Goals for Urinary Albumin/Creatinine Ratio
Dae-Hyun Ko, M.D.1,2*, Sung Woo Lee, M.D.3, Jungwon Hyun, M.D.1, Hyun Soo Kim, M.D.1, Min-Jeong Park, M.D.1, and Dong Hoon Shin, M.D1
Department of Laboratory Medicine1, Hallym University College of Medicine, Hwaseong; Department of Laboratory Medicine2, University of Ulsan College of Medicine and Asan Medical Center, Seoul; Department of Internal Medicine3, Eulji General Hospital, Seoul, Korea
Corresponding author: Dae-Hyun Ko
https://orcid.org/0000-0002-9781-0928
Department of Laboratory Medicine, Hallym University College of Medicine, 7 Keunjaebong-gil, Hwaseong 18450, Korea
Tel: +82-31-8086-3772
Fax: +82-31-8086-2789
*Current address: Department of Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-4504
Fax: +82-2-478-0884
E-mail: daehyuni1118@gmail.com
Received: September 12, 2017; Revised: November 15, 2017; Accepted: May 6, 2018; Published online: September 1, 2018.
© Korean Society for Laboratory Medicine. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background: The urinary albumin/creatinine ratio (ACR) is an important indicator of albuminuria. We aimed to estimate ACR uncertainty and its impact on test results and proposed imprecision quality goals based on the estimated uncertainty.
Methods: The combined ACR uncertainty was calculated using the individual uncertainties of urinary albumin and creatinine. ACR confidence intervals (CIs) were estimated based on the expanded uncertainty. When the CI contained the ACR category boundary (30 or 300 mg/g), the cases were considered ambiguous. Quality goals for ACR were suggested using the number of ambiguous cases among actual patient results.
Results: The number of ambiguous cases resulting from the combined ACR uncertainty was higher than expected based on biological variation (BV) quality goals. When the ACR met BV quality specifications, we estimated that 4.8-15.5% of the results may have been misclassified. To minimize the number of ambiguous results, the minimum, desirable, and optimum quality goals were set at 34.0%, 18.0%, and 4.5%, respectively.
Conclusions: We expressed ACR uncertainty using the uncertainties of urinary albumin and creatinine and assessed the impact of this combined uncertainty on the test results. Subsequently, we proposed imprecision quality goals for ACR based on ambiguous results.
Keywords: Albumin/creatinine ratio, Uncertainty, Reclassification, Quality goal



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