Ann Lab Med 2020; 40(1): 68-71  https://doi.org/10.3343/alm.2020.40.1.68
Evaluating Diagnostic Tests for Helicobacter pylori Infection Without a Reference Standard: Use of Latent Class Analysis
Dong Wook Jekarl, M.D.1,2, Hyunyu Choi, B.S.3, Ji Yeon Kim, M.T.3, Seungok Lee, M.D.2,3, Tae Geun Gweon, M.D.4, Hae Kyung Lee, M.D.2,5, and Yonggoo Kim, M.D.1,2
1Department of Laboratory Medicine, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea; 2Laboratory for Development and Evaluation Center, The Catholic University of Korea, Seoul, Korea; 3Department of Laboratory Medicine, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea; 4Department of Internal Medicine, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea; 5Department of Laboratory Medicine, Uijeongbu St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
Corresponding author: Hae Kyung Lee, M.D.
Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Uijongbu St. Mary’s Hospital, 271 Cheonbo-ro, Uijeongbu 11765, Korea
Tel: +82-31-820-3959 Fax: +82-31-847-6226 E-mail: hkl@catholic.ac.kr
Received: April 28, 2019; Revised: June 10, 2019; Accepted: July 30, 2019; Published online: January 1, 2020.
© 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
Evaluation of diagnostic tests requires reference standards, which are often unavailable. Latent class analysis (LCA) can be used to evaluate diagnostic tests without reference standards, using a combination of observed and estimated results. Conditionally independent diagnostic tests for Helicobacter pylori infection are required. We used LCA to construct a reference standard and evaluate the capability of non-invasive tests (stool antigen test and serum antibody test) to diagnose H. pylori infection compared with the conventional method, where histology is the reference standard. A total of 96 healthy subjects with endoscopy histology results were enrolled from January to July 2016. Sensitivity and specificity were determined for the LCA approach (i.e., using a combination of three tests as the reference standard) and the conventional method. When LCA was used, sensitivity and specificity were 83.8% and 99.4% for histology, 80.0% and 81.9% for the stool antigen test, and 63.6% and 89.3% for the serum antibody test, respectively. When the conventional method was used, sensitivity and specificity were 75.8% and 71.1% for the stool antigen test and 77.7% and 60.7% for the serum antibody test, respectively. LCA can be applied to evaluate diagnostic tests that lack a reference standard.
Keywords: Helicobacter pylori, Latent class analysis, Stool antigen test, Reference standard, Serum antibody test, Diagnosis



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