HL7 CM2 Segment: Clinical Study Schedule Master

The CM2 (Clinical Study Schedule Master) segment defines a single scheduled time point within a clinical study and lists the events expected at that time point. Each CM2 instance names one point on the study calendar (for example a visit day or cycle milestone), describes it, and enumerates the scheduled events. CM2 is the most granular segment of the clinical-study master group, sitting beneath the CM0 (Clinical Study Master) and CM1 (Clinical Study Phase Master) segments that define the study and its phases.

Purpose

CM2 records the visit-and-event schedule of a clinical study. Where CM0 establishes the study and CM1 enumerates its phases, CM2 lays out the time points at which study activities occur and the events scheduled at each. A study commonly carries several CM2 segments, one per scheduled time point, each with a Set ID for ordering, a coded time point, a description, and a repeating list of scheduled events. CM2 completes the structural picture of the protocol carried by the clinical-study master group.

Used in

CM2 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 the master-file record, and CM2 segments follow the CM0 study master and CM1 phase masters to detail the schedule. See MFN messages for the master-file context.

Field-by-field reference

Source: HAPI HL7v2 v2.5.1 javadocs (CM2 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
CM2-1	Set ID - CM2	si	—	R	—	—	Sequence number ordering schedule time points
CM2-2	Scheduled Time Point	ce	—	O	—	—	Coded identifier of the scheduled time point
CM2-3	Description of Time Point	st	—	O	—	—	Free-text description of the time point
CM2-4	Events Scheduled This Time Point	ce	—	O	Y	—	Coded events scheduled at this time point

Most-used fields

CM2-1 Set ID - CM2: orders the time points across the study schedule.
CM2-2 Scheduled Time Point: the coded calendar point (for example Day 1, Week 4) that systems key on.
CM2-3 Description of Time Point: the human-readable label for the time point shown in protocol summaries.
CM2-4 Events Scheduled This Time Point: the repeating list of activities (assessments, labs, procedures) due at the time point.

Version differences (2.3 to 2.8.2)

2.3: CM2 is introduced in the clinical-trials chapter with its four-field structure, including the repeating events field.
2.3.1 through 2.4: Structure is stable; the time point and events fields settle on coded element data types.
2.5 and 2.5.1: Unchanged from 2.4; this page reflects the HAPI v2.5.1 model with CM2-1 through CM2-4, where CM2-2 and CM2-4 use the CE data type and CM2-4 repeats.
2.6 through 2.8.2: CM2 layout is retained without change. As with CM1, the coded data type modernizes in usage, but the four-field shape and the repeating events field are preserved.

Common mistakes

Omitting CM2-1 Set ID. Without it, time points cannot be ordered within the schedule.
Sending only one event in CM2-4 when several are due. CM2-4 repeats; separate multiple events with the repetition separator rather than overwriting.
Confusing CM2-2 Scheduled Time Point with CM1-2 Study Phase Identifier. The phase is the broad protocol stage; the time point is a specific calendar point within it.
Putting event detail in CM2-3. Description is narrative; the actual events belong in the coded, repeating CM2-4.
Sending CM2 without preceding CM0 and CM1 segments. A schedule master is meaningless without the study and phase it elaborates.

Examples

Minimal CM2 (Set ID and time point):

CM2|1|D1^Day 1^L

Fully populated CM2 with repeating events:

CM2|3|W4^Week 4^L|End of cycle 2 assessment visit|VITALS^Vital signs^L~LABS^Laboratory panel^L~IMG^Tumor imaging^L~ECG^Electrocardiogram^L

Annotated breakdown:

CM2|3|W4^Week 4^L|End of cycle 2 assessment visit|VITALS^Vital signs^L~LABS^...~IMG^...~ECG^...
    | |           |                               |
    | |           |                               +-- CM2-4 Events Scheduled This Time Point (CE, repeats with ~)
    | |           +---------------------------------- CM2-3 Description of Time Point (ST)
    | +---------------------------------------------- CM2-2 Scheduled Time Point (CE: code^text^coding system)
    +------------------------------------------------ CM2-1 Set ID - CM2 (SI), orders this time point

CM2-4 repetitions: VITALS (Vital signs), LABS (Laboratory panel), IMG (Tumor imaging), ECG (Electrocardiogram)

In-context excerpt 1, CM2 schedule following CM0 and CM1 inside an MFN master-file message defining a clinical study:

MSH|^~&|STUDYREG|ONCONET|TRIALDB|RESEARCH|20260610093000||MFN^M01|MSG00101|P|2.5.1
MFI|CMA^Clinical Study Master^HL70175|ONCONET|UPD|20260610093000|AL
MFE|MAD|REC0041|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|2|2^Treatment^L|Active treatment phase with study agent ZX in 21-day cycles
CM2|1|D1^Day 1^L|Treatment cycle day 1 visit|VITALS^Vital signs^L~LABS^Laboratory panel^L~DOSE^Study agent administration^L
CM2|2|W4^Week 4^L|End of cycle 2 assessment visit|VITALS^Vital signs^L~LABS^Laboratory panel^L~IMG^Tumor imaging^L

In-context excerpt 2, a follow-up phase schedule with a single event per time point:

MSH|^~&|STUDYREG|ONCONET|TRIALDB|RESEARCH|20260610095500||MFN^M01|MSG00102|P|2.5.1
MFI|CMA^Clinical Study Master^HL70175|ONCONET|UPD|20260610095500|AL
MFE|MAD|REC0050|20260610095500|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|3|3^Follow-up^L|Post-treatment surveillance and survival follow-up
CM2|1|M3^Month 3^L|First follow-up survival check|SURV^Survival status^L
CM2|2|M6^Month 6^L|Second follow-up survival check|SURV^Survival status^L

FHIR mapping

CM2 is not mapped at the segment level. No segment-level ConceptMap is published in the v2-to-FHIR Implementation Guide for CM2. Conceptually, the study schedule maps into PlanDefinition, whose action and timing elements express scheduled time points and the activities due at them, and relates to ResearchStudy for study context. CM2-2 Scheduled Time Point aligns with a PlanDefinition action timing, and CM2-4 Events Scheduled This Time Point with the actions or definitions referenced at that point. These are conceptual alignments, not a normative segment-level mapping.

Engine considerations

Allow multiple CM2 segments per study and per phase; treating CM2 as singular will truncate the schedule.
Preserve repetition on CM2-4 Events Scheduled This Time Point so multiple events at a time point survive transformation.
Maintain the order implied by CM2-1 Set ID so the schedule sequence is retained.
Keep CM2 grouped with the parent CM0 and CM1 segments; do not let routing separate the clinical-study group.
When merging update notifications, reconcile time points by study key (CM0-2), phase (CM1), and CM2-1 Set ID.

How Vorro parses and produces CM2

When parsing inbound CM2, Vorro reads CM2-1 Set ID to order time points and associates each with the study key from CM0-2 and the phase context from the preceding CM1. CM2-2 is decomposed into its CE components as a structured time-point code, CM2-3 is kept as the description, and CM2-4 is expanded into a list of structured event codes rather than collapsed into a single value. Each CM2 record is linked upward to its phase and study.

When producing CM2, Vorro emits one segment per scheduled time point, assigns sequential Set ID values in CM2-1, serializes the structured time-point code into CM2-2, writes the description into CM2-3, and serializes the list of events back into CM2-4 repetitions joined by the repetition separator. Segments are placed after the CM0 and CM1 records so the clinical-study group is well formed.

Sources

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