HL7 CM1 Segment: Clinical Study Phase Master

The CM1 (Clinical Study Phase Master) segment defines a single phase of a clinical study. Each CM1 instance names one phase and gives its description, allowing a study defined by a CM0 (Clinical Study Master) segment to be broken into ordered phases such as screening, treatment, and follow-up. CM1 sits between CM0 above it and the CM2 (Clinical Study Schedule Master) segments that detail the visit schedule within each phase.

Purpose

CM1 records the phase-level structure of a clinical study. Where CM0 establishes the study's identity, CM1 enumerates the phases that make up the study protocol. A study typically has several CM1 segments, one per phase, each carrying a Set ID for ordering, a coded phase identifier, and a free-text description. CM1 itself does not carry visit timing; the schedule of events within a phase is expressed through the CM2 segments that follow it.

Used in

CM1 appears in clinical-study master-file definition segments carried in MFN (Master File Notification) messages that define a clinical trial's structure. The MFE (Master File Entry) segment frames each master-file record, and CM1 segments follow the CM0 study master to enumerate its phases. See MFN messages for the master-file context.

Field-by-field reference

Source: HAPI HL7v2 v2.5.1 javadocs (CM1 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
CM1-1	Set ID - CM1	si	—	R	—	—	Sequence number ordering study phases
CM1-2	Study Phase Identifier	ce	—	O	—	—	Coded identifier of the study phase
CM1-3	Description of Study Phase	st	—	O	—	—	Free-text description of the phase

Most-used fields

CM1-1 Set ID - CM1: orders the phases within the study and links each phase to its CM2 schedule records.
CM1-2 Study Phase Identifier: the coded phase value (for example screening, treatment, follow-up) that downstream systems key on.
CM1-3 Description of Study Phase: the human-readable phase label shown in study catalogs and protocol summaries.

Version differences (2.3 to 2.8.2)

2.3: CM1 is introduced in the clinical-trials chapter with its three-field structure (Set ID, phase identifier, phase description).
2.3.1 through 2.4: Structure is stable; the phase identifier settles on a coded element data type.
2.5 and 2.5.1: Unchanged from 2.4; this page reflects the HAPI v2.5.1 model with CM1-1 through CM1-3, where CM1-2 uses the CE data type.
2.6 through 2.8.2: CM1 layout is retained without change. In later versions the coded data type modernizes (CE toward CWE in usage), but the three-field shape is preserved.

Common mistakes

Omitting CM1-1 Set ID. Without a sequence number, phases cannot be ordered and CM2 schedule records cannot be associated with the correct phase.
Reusing Set ID values across phases. Each CM1 in a study must carry a distinct Set ID.
Putting visit or event timing in CM1-3. Description is narrative only; scheduled events belong in CM2.
Sending CM1 without a preceding CM0. A phase master is meaningless without the study master that defines the study it belongs to.
Treating CM1-2 as free text. It is a coded element (CE); send a code and coding system, not just a display string.

Examples

Minimal CM1 (Set ID and phase identifier):

CM1|1|1^Screening^L

Fully populated CM1:

CM1|2|2^Treatment^L|Active treatment phase with study agent ZX administered in 21-day cycles

Annotated breakdown:

CM1|2|2^Treatment^L|Active treatment phase with study agent ZX...
    | |             |
    | |             +-- CM1-3 Description of Study Phase (ST)
    | +---------------- CM1-2 Study Phase Identifier (CE: code^text^coding system)
    +------------------ CM1-1 Set ID - CM1 (SI), orders this phase within the study

CM1-2 components: 2 = code, Treatment = display text, L = local coding system

In-context excerpt 1, CM1 phases following CM0 inside an MFN master-file message defining a clinical study:

MSH|^~&|STUDYREG|ONCONET|TRIALDB|RESEARCH|20260610093000||MFN^M01|MSG00091|P|2.5.1
MFI|CMA^Clinical Study Master^HL70175|ONCONET|UPD|20260610093000|AL
MFE|MAD|REC0021|20260610093000|CT-2026-0042^^ONCONET^STUDYID|CE
CM0|1|CT-2026-0042^^ONCONET^STUDYID||Phase II Trial of Agent ZX in Advanced Solid Tumors|4471^Mercado^Lena^A^^Dr^MD^^ONCONET|20260115|128|20260601
CM1|1|1^Screening^L|Pre-treatment eligibility and baseline assessments
CM1|2|2^Treatment^L|Active treatment phase with study agent ZX in 21-day cycles
CM1|3|3^Follow-up^L|Post-treatment surveillance and survival follow-up

In-context excerpt 2, a single-phase study where CM1 is followed by its CM2 schedule:

MSH|^~&|STUDYREG|ONCONET|TRIALDB|RESEARCH|20260610095000||MFN^M01|MSG00092|P|2.5.1
MFI|CMA^Clinical Study Master^HL70175|ONCONET|UPD|20260610095000|AL
MFE|MAD|REC0030|20260610095000|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
CM1|1|1^Treatment^L|Single-arm treatment phase, regimen QB, six cycles
CM2|1|D1^Day 1^L|First treatment day of each cycle|VITALS^Vital signs^L~LABS^Laboratory panel^L

FHIR mapping

CM1 is not mapped at the segment level. No segment-level ConceptMap is published in the v2-to-FHIR Implementation Guide for CM1. Conceptually, study phases map into the FHIR ResearchStudy resource, where ResearchStudy.phase carries the trial phase, and into PlanDefinition for protocol structure. CM1-2 Study Phase Identifier aligns with ResearchStudy.phase, and CM1-3 with a human-readable description element. These are conceptual alignments, not a normative segment-level mapping.

Engine considerations

Configure engines to allow multiple CM1 segments per study; a one-CM1-per-message assumption will drop later phases.
Preserve the order implied by CM1-1 Set ID so phase sequencing survives transformation.
Keep CM1 grouped with its parent CM0 and child CM2 segments; do not let routing rules separate the group.
Parse CM1-2 as a coded element so the code, text, and coding system components are retained rather than concatenated.
When merging update notifications, reconcile phases by the combination of study key (from CM0-2) and CM1-1 Set ID.

How Vorro parses and produces CM1

When parsing inbound CM1, Vorro reads CM1-1 Set ID to order phases and associates each phase with the study key carried in the preceding CM0-2. CM1-2 is decomposed into its CE components (code, text, coding system) and stored as a structured phase code, while CM1-3 is retained as the phase description. Each CM1 record is linked upward to its CM0 and downward to any CM2 schedule segments sharing the same phase context.

When producing CM1, Vorro emits one segment per study phase, assigns sequential Set ID values in CM1-1, serializes the structured phase code back into CM1-2 as a coded element, and writes the description into CM1-3. Segments are placed after the CM0 study master and before the related CM2 segments so the clinical-study group is well formed.

Sources

← Back to HL7 v2 Guide