HL7 CM0 Segment: Clinical Study Master

The CM0 (Clinical Study Master) segment carries the top-level master definition of a clinical study. It identifies the study to a receiving system and records its administrative core: the sponsor's study identifier, the descriptive title, the study chairman, and Institutional Review Board (IRB) and accrual milestones. CM0 is the anchor segment of the clinical-study master group, with CM1 (phases) and CM2 (schedule) defining the study's internal structure beneath it.

Purpose

CM0 establishes the identity and administrative metadata of a clinical study within a master-file exchange. A single CM0 instance describes one study, providing the sponsor study ID that downstream segments and messages reference. It captures the people and dates that govern the study at the master level: the chairman, study contacts, the last IRB approval date, and accrual figures. CM0 does not describe phases or visit schedules itself; those are carried in the related CM1 and CM2 segments that follow it in the same master-file definition.

Used in

CM0 appears in clinical-study master-file definition segments carried in MFN (Master File Notification) messages that define a clinical trial's structure. Within an MFN message, an MFE (Master File Entry) segment introduces each master-file record, and the CM0/CM1/CM2 group then supplies the clinical-study definition. See MFN messages for how the master-file framing wraps these segments.

Field-by-field reference

Source: HAPI HL7v2 v2.5.1 javadocs (CM0 javadoc) for sequence, name, data type, and repetition. Length is not published in the javadocs (—); Required and Table # are filled from the HL7 v2.5.1 standard where well-established.

Seq	Name	Data Type	Length	Req	Repeat	Table #	Description
CM0-1	Set ID - CM0	si	—	O	—	—	Sequence number for this CM0 record
CM0-2	Sponsor Study ID	ei	—	R	—	—	Sponsor's primary study identifier
CM0-3	Alternate Study ID	ei	—	O	Y	—	Additional identifiers for the study
CM0-4	Title of Study	st	—	O	—	—	Descriptive title of the study
CM0-5	Chairman of Study	xcn	—	O	Y	—	Person chairing the clinical study
CM0-6	Last IRB Approval Date	dt	—	O	—	—	Date of most recent IRB approval
CM0-7	Total Accrual to Date	nm	—	O	—	—	Cumulative subject accrual count
CM0-8	Last Accrual Date	dt	—	O	—	—	Date of most recent subject accrual
CM0-9	Contact for Study	xcn	—	O	Y	—	Contact person for the study
CM0-10	Contact's Telephone Number	xtn	—	O	—	—	Telephone number of the contact
CM0-11	Contact's Address	xad	—	O	Y	—	Mailing address of the contact

Most-used fields

CM0-2 Sponsor Study ID: the normalized identifier that uniquely names the study and is referenced across the master-file group.
CM0-4 Title of Study: the human-readable study title shown in catalogs and registries.
CM0-5 Chairman of Study: the principal accountable investigator at the master level.
CM0-6 Last IRB Approval Date: a governance milestone gating whether the study may accrue subjects.
CM0-9 Contact for Study: the operational point of contact paired with CM0-10 and CM0-11.

Version differences (2.3 to 2.8.2)

2.3: CM0 is defined as part of the clinical-trials chapter; the eleven-field structure (sponsor study ID, title, chairman, IRB and accrual dates, contact details) is established here.
2.3.1 through 2.4: Field set and data types remain stable; identifier fields settle on the EI data type for study identifiers.
2.5 and 2.5.1: Structure is unchanged from 2.4; this page reflects the HAPI v2.5.1 model with CM0-1 through CM0-11.
2.6 through 2.8.2: CM0 continues unchanged in layout. The clinical-study segments are retained but rarely implemented, as study definitions increasingly move to dedicated research data standards.

Common mistakes

Omitting CM0-2 Sponsor Study ID. This is the study's primary key; without it, CM1 and CM2 records cannot be tied to a study.
Treating CM0-3, CM0-5, CM0-9, or CM0-11 as single-valued. The javadoc shows these as repeating; collapsing repetitions loses alternate IDs, co-chairs, or multiple contacts.
Confusing CM0-5 Chairman of Study with CM0-9 Contact for Study. The chairman is the accountable investigator; the contact is the operational liaison.
Placing schedule or phase data in CM0. Phases belong in CM1 and visit schedules in CM2; CM0 is administrative only.
Free-texting dates in CM0-6 and CM0-8. These are DT fields and must be valid HL7 dates (YYYY[MM[DD]]).

Examples

Minimal CM0 (sponsor study ID only):

CM0|1|CT-2026-0042^^ONCONET^STUDYID

Fully populated CM0:

CM0|1|CT-2026-0042^^ONCONET^STUDYID|ALT-77A^^REGISTRY^STUDYID~NCI-9931^^NCI^STUDYID|Phase II Trial of Agent ZX in Advanced Solid Tumors|4471^Mercado^Lena^A^^Dr^MD^^ONCONET|20260115|128|20260601|7752^Okafor^Daniel^^^^RN^^ONCONET|^WPN^PH^^1^512^5550173|400 Research Pkwy^Suite 210^Austin^TX^78701^USA

Annotated breakdown:

CM0|1|CT-2026-0042^^ONCONET^STUDYID|...|Phase II Trial of Agent ZX...|4471^Mercado^Lena...
    |  |                                  |                              |
    |  |                                  |                              +-- CM0-5 Chairman of Study (XCN)
    |  |                                  +--------------------------------- CM0-4 Title of Study (ST)
    |  +------------------------------------------------------------------- CM0-2 Sponsor Study ID (EI)
    +---------------------------------------------------------------------- CM0-1 Set ID (SI)

CM0-3 (Alternate Study ID) repeats with ~ : ALT-77A^^REGISTRY^STUDYID~NCI-9931^^NCI^STUDYID
CM0-6 Last IRB Approval Date = 20260115   --> 2026-01-15
CM0-7 Total Accrual to Date  = 128
CM0-8 Last Accrual Date      = 20260601   --> 2026-06-01

In-context excerpt 1, CM0 introduced by MFI/MFE inside an MFN master-file message defining a clinical study:

MSH|^~&|STUDYREG|ONCONET|TRIALDB|RESEARCH|20260610093000||MFN^M01|MSG00081|P|2.5.1
MFI|CMA^Clinical Study Master^HL70175|ONCONET|UPD|20260610093000|AL
MFE|MAD|REC0001|20260610093000|CT-2026-0042^^ONCONET^STUDYID|CE
CM0|1|CT-2026-0042^^ONCONET^STUDYID|NCI-9931^^NCI^STUDYID|Phase II Trial of Agent ZX in Advanced Solid Tumors|4471^Mercado^Lena^A^^Dr^MD^^ONCONET|20260115|128|20260601|7752^Okafor^Daniel^^^^RN^^ONCONET|^WPN^PH^^1^512^5550173|400 Research Pkwy^Suite 210^Austin^TX^78701^USA

In-context excerpt 2, CM0 anchoring a study that also carries phase and schedule masters:

MSH|^~&|STUDYREG|ONCONET|TRIALDB|RESEARCH|20260610094500||MFN^M01|MSG00082|P|2.5.1
MFI|CMA^Clinical Study Master^HL70175|ONCONET|UPD|20260610094500|AL
MFE|MAD|REC0010|20260610094500|CT-2026-0058^^ONCONET^STUDYID|CE
CM0|1|CT-2026-0058^^ONCONET^STUDYID||Randomized Study of Regimen QB in Stage III Disease|5012^Vance^Priya^^^Dr^MD^^ONCONET|20260204|64|20260520|7790^Reyes^Marco^^^^RN^^ONCONET|^WPN^PH^^1^512^5550199|17 Clinical Way^^Austin^TX^78702^USA
CM1|1|1^Screening^L|Pre-treatment eligibility and baseline assessments
CM2|1|D1^Day 1^L|Treatment cycle day 1 visit|VITALS^Vital signs^L~LABS^Laboratory panel^L

FHIR mapping

CM0 is not mapped at the segment level. No segment-level ConceptMap is published in the v2-to-FHIR Implementation Guide for CM0. Conceptually, the clinical-study master maps to the FHIR ResearchStudy resource (study identity, title, sponsor, principal investigator) and, for protocol-level definition, to PlanDefinition. The sponsor study ID (CM0-2) aligns with ResearchStudy.identifier, CM0-4 with ResearchStudy.title, and CM0-5 with ResearchStudy.principalInvestigator. These are conceptual alignments, not a normative segment-level mapping.

Engine considerations

Most interface engines retain CM0 as a generic or custom segment, since clinical-study segments are infrequently configured out of the box. Confirm the segment is present in the message profile before routing.
Preserve repetition on CM0-3, CM0-5, CM0-9, and CM0-11. Engines that flatten repetitions silently drop alternate study IDs and co-investigators.
Keep the CM0/CM1/CM2 group together during transformation. Splitting the group orphans phase and schedule records from their parent study.
Validate DT fields (CM0-6, CM0-8) on ingest; reject or quarantine malformed dates rather than passing them downstream.
Treat CM0-2 as the join key when reconciling updates from repeated MFN notifications.

How Vorro parses and produces CM0

When parsing inbound CM0, Vorro reads CM0-2 Sponsor Study ID as the study primary key and normalizes its EI components (entity identifier, namespace ID, universal ID, and type) into a structured study record. Repeating fields (CM0-3 alternate IDs, CM0-5 chairmen, CM0-9 contacts, CM0-11 addresses) are expanded into lists rather than collapsed, and DT fields are parsed into normalized dates. The CM0 record is linked to any CM1 and CM2 segments in the same MFN group.

When producing CM0, Vorro emits CM0-1 as a sequence number, writes the study key into CM0-2, and serializes list-valued source data back into repetitions joined by the repetition separator. Dates are formatted as valid HL7 DT values, and the segment is placed after its MFE within the master-file structure so the clinical-study group is well formed.

Sources

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