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. 2018 Nov 5;4(4):e10770. doi: 10.2196/10770

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©Richard M Selik, Laurie Linley. Originally published in JMIR Public Health and Surveillance (http://publichealth.jmir.org), 05.11.2018.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in JMIR Public Health and Surveillance, is properly cited. The complete bibliographic information, a link to the original publication on http://publichealth.jmir.org, as well as this copyright and license information must be included.

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Test sequences defining stage 0 preliminary subgroups. Superscripts are as follows: a) Positive “antibody” test results include positive results from the antigen component or the antibody component of combination antigen or antibody tests. b) “Negative antibody” test results include indeterminate results from supplemental immunoglobulin G–only supplemental antibody tests and negative results from antigen or antibody tests in which only the antibody component is negative or in which both the antigen and antibody components are negative. c) Positive nucleic acid tests (NATs) include qualitative and quantitative (viral load) tests. d) Negative NATs include only qualitative NATs.