Introduction to CDISC ODM

What Is CDISC ODM?

CDISC ODM is a vendor-neutral, platform-independent format. CDISC ODM supports the electronic acquisition, exchange, and archival of clinical trials data for the medical and biopharmaceutical industries.

PROC CDISC supports CDISC ODM version 1.2.

CDISC ODM Basics

CDISC ODM defines the following entities to represent clinical trials (study) data:

item

describes an individual study item, such as a single blood pressure reading.

item group

describes a closely related set of study items that are usually analyzed together.

form

describes logically or temporally related information. Forms can contain multiple item groups.

study event

describes a data collection event such as a patient visit. A series of forms might be collected as part of a study event. A study event is associated with a specific patient in the study.

CDISC ODM defines the following metadata to describe the types of study events, forms, item groups, and items that are allowed in the study:

StudyEventDef

describes a particular instance of a study event.

FormDef

describes a particular instance of a form.

ItemDef

describes a particular instance of an item.

ItemGroupDef

describes a particular instance of an item group.

CodeList

defines a discrete set of permitted values for an item or a more human-readable description of an encoded value.

Metadata contains internal and external attributes that identify the entity for which information is provided. The internal attributes designate entities within the model and allow cross-references to be defined between entities, both within and between CDISC ODM XML documents. Internal attributes include an object instance identifier (OID), a subject key, and repeat keys.

An OID uniquely identifies each entity. For example, a StudyOID is assigned to uniquely identify each study, a StudyEventOID is assigned to uniquely identify each StudyEventDef within a study, a FormOID is assigned to uniquely identify each form used in a StudyEventDef, and so on.
The subject key identifies a subject within a study.
The repeat key identifies an entity as one of a series. For example, there can be several study events of a particular type for a particular subject. The repeat key temporarily relates the distinct study events to each other.

The external attributes are used by clinical personnel to specify information that is unique to the entity. These attributes include subject randomization codes, site codes, and so on. Within CDISC ODM, the attributes are treated as part of the clinical trials data.

The set of attributes that are required to reference a single entity is referred to as a KeySet. For more information about the CDISC ODM KeySet, see CDISC ODM KeySet Members.