SDTM


SDTM defines a standard structure for human clinical trial data tabulations and for nonclinical study data tabulations that are to be submitted as part of a product application to a regulatory authority such as the United States Food and Drug Administration. The Submission Data Standards team of Clinical Data Interchange Standards Consortium defines SDTM.
On July 21, 2004, SDTM was selected as the standard specification for submitting tabulation data to the FDA for clinical trials and on July 5, 2011 for nonclinical studies. Eventually, all data submissions will be expected to conform to this format. As a result, clinical and nonclinical Data Managers will need to become proficient in the SDTM to prepare submissions and apply the SDTM structures, where appropriate, for operational data management.

Background

SDTM is built around the concept of observations collected about subjects who participated in a clinical study. Each observation can be described by a series of variables, corresponding to a row in a dataset or table. Each variable can be classified according to its Role. A Role determines the type of information conveyed by the variable about each distinct observation and how it can be used. Variables can be classified into four major roles:
A fifth type of variable role, Rule, can express an algorithm or executable method
to define start, end, or looping conditions in the Trial Design model.
The set of Qualifier variables can be further categorized into five sub-classes:
For example, in the observation, 'Subject 101 had mild nausea starting on Study Day 6,' the Topic variable value is the term for the adverse event, 'NAUSEA'. The Identifier variable is the subject identifier, '101'. The Timing variable is the study day of the start of the event, which captures the information, 'starting on Study Day 6', while an example of a Record Qualifier is the severity, the value for which is 'MILD'.
Additional Timing and Qualifier variables could be included to provide the necessary detail to adequately describe an observation.• The SDTM addition to PROC CDISC does not convert existing SDS 2.x content to SDTM 3.x representations.

Datasets and domains

Observations are normally collected for all subjects in a series of domains. A domain is defined as a collection of logically-related observations with a topic-specific commonality about the subjects in the trial. The logic of the relationship may relate to the scientific matter of the data, or to its role in the trial.
Typically, each domain is represented by a dataset, but it is possible to have information relevant to the same topicality spread among multiple datasets. Each dataset is distinguished by a unique, two-character DOMAIN code that should be used consistently throughout the submission. This DOMAIN code is used in the dataset name, the value of the DOMAIN variable within that dataset, and as a prefix for most variable names in the dataset.
The dataset structure for observations is a flat file representing a table with one or more rows and columns. Normally, one dataset is submitted for each domain. Each row of the dataset represents a single observation and each column represents one of the variables. Each dataset or table is accompanied by metadata definitions that provide information about the variables used in the dataset. The metadata are described in a data definition document named 'Define' that is submitted along with the data to regulatory authorities.
Submission Metadata Model uses seven distinct metadata attributes to be defined for each dataset variable in the metadata definition document:
Data stored in dataset variables include both raw and derived values. In SDTM only the name, label, and type are listed with a set of CDISC guidelines that provide a general description for each variable used by a general observation class.
Comments are included as necessary according to the needs of individual studies.
The presence of an asterisk in the 'Controlled Terms or Format' column indicates that a discrete set of values is expected to be made available for this variable. This set of values may be sponsor-defined in cases where standard vocabularies have not yet been defined or from an external published source such as MedDRA.
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Special-purpose domains

The CDISC Version 3.x Submission Data Domain Models include special-purpose domains with a specific
structure and cannot be extended with any additional qualifier or timing variables other than those specified.
Additional fixed structure, non-extensible special-purpose domains are discussed in the Trial Design model.

The general domain classes

Most observations collected during the study should be divided among three general observation classes: Interventions, Events, or Findings:
In most cases, the identification of the general class appropriate to a specific collection of data by topicality is straightforward. Often the Findings general class is the best choice for general observational data collected as measurements or responses to questions. In cases when the topicality may not be as clear, the choice of class may be based more on the scientific intent of the protocol or analysis plan or the data structure.
All datasets based on any of the general observation classes share a set of common Identifier variables and Timing variables. Three general rules apply when determining which
variables to include in a domain:
Special-Purpose Domains:
Interventions General Observation Class:
Events General Observation Class:''
Findings General Observation Class:
Findings About :
Trial Design Domains:
Special-Purpose Relationship Datasets:
One criticism of the SDTM standards is that they are continually changing, with new versions released frequently. CDISC claims that SDTM standards are backward compatible. But the claim is unreliable. It is not possible to map the data from EDC DBMS to SDTM standards until the clinical trial completes. New domains, for example the exposure as collected domain, were added recently. However, backward compatibility with earlier domains is not always possible. The standards are not reliable, and well evolved. The controlled terminology is a very small subset of National Cancer institute terminology.