This code system http://terminology.hl7.org/CodeSystem/state-change-reason defines the following codes:

CodeDisplayDefinition
adverseEvent adverse eventadverse event.
death death (adverse event)death (adverse event).
notEligible did not meet eligibility criteriadid not meet eligibility criteria.
eligibleButNo eligible but unwilling or unable to participateeligible but unwilling or unable to participate.
enrolled enrolled or registeredenrolled or registered.
exclusion exclusionexclusion.
followUpComplete follow-up completefollow-up complete.
inclusion inclusioninclusion.
informedConsentSigned Informed consent signedInformed consent signed.
intOrObsComplete intervention or observation completeintervention or observation complete.
nonCompliance non-compliancenon-compliance.
preReg pre-registered or slot reservedpre-registered or slot reserved.
refuseConsent refuse consentrefuse consent.
screenFailure screen failurescreen failure.
studyClosed study permanently closed to accrualstudy permanently closed to accrual.
studyTerminated study terminatedstudy terminated.
subjectRefusal subject refusalsubject refusal.
unwillingOrUnable unwilling or unable to participateunwilling or unable to participate.
withdrawnConsent withdrawn consentwithdrawn consent.
diseaseRelapse Disease RelapseRelapse of disease.
failedRandomization Failed RandomizationSubject failed randomization.
lackOfEfficacy Lack Of EfficacyThe study activities were not efficient in dealing with the underlying issue.
lostToFollowUp Lost To Follow UpThe subject can no longer be followed up.
physicianDecision Physician DecisionA physician has decided the subject should no longer continue on the study.
pregnancy PregnancySubject is now pregnant and no longer meets the inclusion criteria.
progressiveDisease Progressive DiseaseThe subject has a disease that has progressed to far to allow them to continue in the study.
protocolDeviation Protocol DeviationThere has been a protocol deviation that cannot be corrected or compensated for.
recovery RecoveryThe subject has recovered and no longer meets the inclusion criteria.
siteTerminated Site TerminatedThe site where the subject was being treated is no longer in the study.
technicalProblems Technical ProblemsThe subject cannot continue on the study due to technical issues.
complete CompleteThe study is now complete.
<status value="active"/><experimental value="false"/><date value="2020-12-28T16:55:11+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="Indicates why the state of the subject changed."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/state-change-reason"/><content value="complete"/><concept><code value="adverseEvent"/><display value="adverse event"/><definition value="adverse event."/></concept><concept><code value="death"/><display value="death (adverse event)"/><definition value="death (adverse event)."/></concept><concept><code value="notEligible"/><display value="did not meet eligibility criteria"/><definition value="did not meet eligibility criteria."/></concept><concept><code value="eligibleButNo"/><display value="eligible but unwilling or unable to participate"/><definition value="eligible but unwilling or unable to participate."/></concept><concept><code value="enrolled"/><display value="enrolled or registered"/><definition value="enrolled or registered."/></concept><concept><code value="exclusion"/><display value="exclusion"/><definition value="exclusion."/></concept><concept><code value="followUpComplete"/><display value="follow-up complete"/><definition value="follow-up complete."/></concept><concept><code value="inclusion"/><display value="inclusion"/><definition value="inclusion."/></concept><concept><code value="informedConsentSigned"/><display value="Informed consent signed"/><definition value="Informed consent signed."/></concept><concept><code value="intOrObsComplete"/><display value="intervention or observation complete"/><definition value="intervention or observation complete."/></concept><concept><code value="nonCompliance"/><display value="non-compliance"/><definition value="non-compliance."/></concept><concept><code value="preReg"/><display value="pre-registered or slot reserved"/><definition value="pre-registered or slot reserved."/></concept><concept><code value="refuseConsent"/><display value="refuse consent"/><definition value="refuse consent."/></concept><concept><code value="screenFailure"/><display value="screen failure"/><definition value="screen failure."/></concept><concept><code value="studyClosed"/><display value="study permanently closed to accrual"/><definition value="study permanently closed to accrual."/></concept><concept><code value="studyTerminated"/><display value="study terminated"/><definition value="study terminated."/></concept><concept><code value="subjectRefusal"/><display value="subject refusal"/><definition value="subject refusal."/></concept><concept><code value="unwillingOrUnable"/><display value="unwilling or unable to participate"/><definition value="unwilling or unable to participate."/></concept><concept><code value="withdrawnConsent"/><display value="withdrawn consent"/><definition value="withdrawn consent."/></concept><concept><code value="diseaseRelapse"/><display value="Disease Relapse"/><definition value="Relapse of disease."/></concept><concept><code value="failedRandomization"/><display value="Failed Randomization"/><definition value="Subject failed randomization."/></concept><concept><code value="lackOfEfficacy"/><display value="Lack Of Efficacy"/><definition value="The study activities were not efficient in dealing with the underlying issue."/></concept><concept><code value="lostToFollowUp"/><display value="Lost To Follow Up"/><definition value="The subject can no longer be followed up."/></concept><concept><code value="physicianDecision"/><display value="Physician Decision"/><definition value="A physician has decided the subject should no longer continue on the study."/></concept><concept><code value="pregnancy"/><display value="Pregnancy"/><definition value="Subject is now pregnant and no longer meets the inclusion criteria."/></concept><concept><code value="progressiveDisease"/><display value="Progressive Disease"/><definition value="The subject has a disease that has progressed to far to allow them to continue in the study."/></concept><concept><code value="protocolDeviation"/><display value="Protocol Deviation"/><definition value="There has been a protocol deviation that cannot be corrected or compensated for."/></concept><concept><code value="recovery"/><display value="Recovery"/><definition value="The subject has recovered and no longer meets the inclusion criteria."/></concept><concept><code value="siteTerminated"/><display value="Site Terminated"/><definition value="The site where the subject was being treated is no longer in the study."/></concept><concept><code value="technicalProblems"/><display value="Technical Problems"/><definition value="The subject cannot continue on the study due to technical issues."/></concept><concept><code value="complete"/><display value="Complete"/><definition value="The study is now complete."/></concept></CodeSystem>