This case-sensitive code system http://terminology.hl7.org/CodeSystem/variant-state defines the following codes:

CodeDefinition
positive the variant is detected.
negative no variant is detected.
absent result of the variant is missing.
 <status value="draft"/> <experimental value="false"/> <date value="2020-04-09T21:10:28+00:00"/> <publisher value="Health Level Seven International"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org"/> </telecom> <telecom> <system value="email"/> <value value="hq@HL7.org"/> </telecom> </contact> <description value="Codes providing the status of the variant test result."/> <copyright value="This material derives from the HL7 Terminology (THO). THO is copyright ©1989+ Health Level Seven International and is made available under the CC0 designation. For more licensing information see: https://terminology.hl7.org/license"/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/variant-state"/> <content value="complete"/> <concept> <code value="positive"/> <display value="positive"/> <definition value="the variant is detected."/> </concept> <concept> <code value="negative"/> <display value="negative"/> <definition value="no variant is detected."/> </concept> <concept> <code value="absent"/> <display value="absent"/> <definition value="result of the variant is missing."/> </concept> </CodeSystem>