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Data element - A unit of data that cannot be decomposed into more
pieces of information that have useful meanings within the scope of their application,
whether that application be data collection or data sharing. Data elements are the
fundamental units of data an organization manages and are the common units for transferring
information from one organization to another regardless of the data system(s) used.
A data element is usually represented as a field on a case report form (CRF). Sometimes
however, data elements are derived from existing data elements or from the metadata
(i.e. the data about the data). In a relational database a data element is commonly
represented as a field or column in a table.
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Common data element (CDE) – A data element that can be used in
multiple clinical studies and is required to publish primary papers reporting the
results of a clinical study. Considering the aforementioned criteria, not all data
elements qualify as CDEs; the CDEs are a subset of the universe of all data elements.
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Common data grouping (CDG) – A logical collection of one or more
related CDEs. Some CDGs are equivalent to a single CDE and others are comprised
of multiple CDEs. It is highly recommended that all CDEs be collected for a particular
CDG to ensure the data are meaningful. Whereas a CDE has a direct relationship with
a variable that is stored in a data system, a CDG does not as its purpose is arranging
elements conceptually and facilitating data clarity.
The following three examples serve to illustrate the CDE and CDG definitions. The CDEs
are bolded for easy reference.
Example #1 - Vital Signs, Height and Weight CRF:
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Data Element
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Definition
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Common Data Element (CDE)?
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Common Data Grouping (CDG)
Name
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Date
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Date vitals, height and
weight were taken
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Yes
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Vital Signs Time of Measurement
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Time Value
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Indicates the numeric
time vitals, height and weight were taken
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Yes
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Time Unit
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Indicates whether time
of vitals, height and weight is AM, PM, or 24-hour clock
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Yes
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Pulse Value
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Pulse measurement in beats
per minute (bpm)
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Yes
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Pulse
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Pulse Not Collected
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To be selected if pulse
value was not collected
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Yes
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Systolic Blood Pressure
Value
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Systolic Blood Pressure
measurement in Torr
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Yes
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Blood Pressure
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Diastolic Blood Pressure
Value
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Diastolic Blood Pressure
measurement in Torr
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Yes
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Blood Pressure Not Collected
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To be selected if blood
pressure value was not collected
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Yes
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Temperature Value
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Temperature measurement
in degrees
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Yes
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Temperature
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Temperature Unit
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Indicates whether temperature
measured in degrees Fahrenheit (oF) or degrees Celsius (oC)
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Yes
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Temperature Not Collected
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To be selected if temperature
value was not collected
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Yes
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Weight Value
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Measurement of the subject's
weight as taken at the time of visit (not self-reported)
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Yes
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Weight
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Weight Unit
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Indicates whether weight
measured in pounds (lbs) or kilograms (kg)
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Yes
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Weight Not Collected
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To be selected if weight
value was not collected
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Yes
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Height Value
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Measurement of the subject's
height as taken at the time of visit (not self-reported)
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Yes
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Height
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Height Unit
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Indicates whether height
measured in inches (in) or centimeters (cm)
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Yes
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Height Not Collected
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To be selected if height
value was not collected
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Yes
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Please Note: The units that temperature,
weight, and height are measured in are CDEs. This highlights that the CDE
designation illustrates what data are important to collect but still gives studies
the flexibility to decide the best way to collect those data.
Example #2 - NIH Stroke Scale (NIHSS) CRF:
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Data Element
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Definition
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Common Data Element (CDE)?
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Common Data Grouping (CDG)
Name
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NIHSS Date
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Date NIHSS performed
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Yes
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NIH Stroke Scale Time
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NIHSS Time Value
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Time NIHSS performed
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Yes
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NIHSS Time Unit
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Indicates whether time of NIHSS
is AM, PM, or 24-hour clock
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Yes
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NIHSS Total Score
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NIH Stroke Scale (NIHSS) Total
Score
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Yes
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NIH Stroke Scale Score
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Level of Consciousness Score
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1a. Level of Consciousness: The
investigator must choose a response if a full evaluation is prevented by such obstacles
as an endotracheal tube, language barrier, orotracheal trauma/bandages. A 3 is scored
only if the subjectmakes no movement (other than reflexive posturing) in response
to noxious stimulation.
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Yes
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LOC Questions Score
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1b. LOC Questions: The subject is
asked the month and his/her age. The answer must be correct - there is no partial
credit for being close. Aphasic and stuporous patients who do not comprehend the
questions will score 2. Patients unable to speak because of endotracheal intubation,
orotracheal trauma, severe dysarthria from any cause, language barrier, or any other
problem not secondary to aphasia are given a 1. It is important that only the initial
answer be graded and that the examiner not "help" the subject with verbal or non-verbal
cues.
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Yes
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LOC Commands Score
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1c. LOC Commands: The subject is
asked to open and close the eyes and then to grip and release the non-paretic hand.
Substitute another one step command if the hands cannot be used. Credit is given
if an unequivocal attempt is made but not completed due to weakness. If the subjectdoes
not respond to command, the task should be demonstrated to him or her (pantomime),
and the result scored (i.e., follows none, one or two commands). Patients with trauma,
amputation, or other physical impediments should be given suitable one-step commands.
Only the first attempt is scored.
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Yes
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Best Gaze Score
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2. Best Gaze: Only horizontal eye
movements will be tested. Voluntary or reflexive (oculocephalic) eye movements will
be scored, but caloric testing is not done. If the subjecthas a conjugate deviation
of the eyes that can be overcome by voluntary or reflexive activity, the score will
be 1. If a subjecthas an isolated peripheral nerve paresis (CN III, IV or VI), score
a 1. Gaze is testable in all aphasic patients. Patients with ocular trauma, bandages,
pre-existing blindness, or other disorder of visual acuity or fields should be tested
with reflexive movements, and a choice made by the investigator. Establishing eye
contact and then moving about the subjectfrom side to side will occasionally clarify
the presence of a partial gaze palsy.
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Yes
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... (etc. NIHSS Questions 3
- 10)
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Yes
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Extinction and Inattention Score
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11. Extinction and Inattention (formerly
Neglect): Sufficient information to identify neglect may be obtained during the
prior testing. If the subject has a severe visual loss preventing visual double
simultaneous stimulation, and the cutaneous stimuli are normal, the score is normal.
If the subject has aphasia but does appear to attend to both sides, the score is
normal. The presence of visual spatial neglect or anosagnosia may also be taken
as evidence of abnormality. Since the abnormality is scored only if present, the
item is never untestable.
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Yes
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Please Note: The NIHSS Stroke Scale
Score is a CDG and its CDEs are the total score and all the sub-scores that are
summed to derive the total.
Example #3 - Concomitant Medications CRF:
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Data Element
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Definition
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Common Data Element (CDE)?
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Common Data Grouping (CDG)
Name
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Reported name of medication
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Verbatim name of the medication
the subject took during the study.
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Yes
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Single concomitant medication
record
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Duration
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Period of time subject
took medication during the study.
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Yes
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Start Date
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Date the subject first took
the medication.
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No
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N/A
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End/Stop Date
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Date the subject stopped
taking the medication.
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No
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N/A
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Ongoing/Continuing
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Indicates whether the medication
is ongoing/continuing at the point of data collection.
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No
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N/A
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Dose per Administration
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Dose of medication taken
per administration.
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No
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N/A
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Dose Unit
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Unit associated with the
dose per administration.
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No
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N/A
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Indication
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Reason for administration
of the medication.
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No
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N/A
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No Concomitant Medications
Taken
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Checked/selected if the
subject did not take any concomitant medications.
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Yes
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No Concomitant Medications
Taken
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Please Note: Several data elements
that are often found on concomitant medication CRFs do not qualify as CDEs.
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CDEs Toolbox: – In order for a CDE to be useful, its name as well
as the instructions for collecting, deriving, and checking its value need to be
the same in different clinical studies. The data collection information content
for each CDE is described by a data dictionary.
Each CDE corresponds to a single entry in a data dictionary. A given CDG corresponds
to a single entry in a data dictionary or multiple entries, depending upon the number
of CDEs that comprise it.
Each data dictionary entry specifies the name, definition, recommended data type
and size, and permissible values of the CDE for data collection purposes. The data
dictionary is accompanied by a set of instructions for collecting, and if applicable
deriving, the CDE in the Manual of Procedures (MOP) for the clinical study.
In addition, there are associated algorithms used for checking the validity of a
CDE’s value based on ranges of normal values, permissible extremes, and relationships
to other CDEs.
Sample data collection forms are provided to logically organize the CDEs and depict
the relationships between the CDEs. The template forms were created to facilitate
the understanding of the implementation of the CDEs. Sites may need to add additional
data elements to the template forms depending upon the study protocol.
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Other Pertinent Definitions for the CDEs project:
Core – CDEs that are collected by all clinical studies regardless of disease
or therapeutic area. For example the CDEs collected on the following forms are “core”
CDEs: Patient Characteristics, General Physical Exam, and Adverse Events.
Branch – CDEs that are only collected by studies of a specific disease or
therapeutic area. The first two “branches” developed for the CDEs project were Stroke
and Parkinson’s disease (PD). There will likely be sub-branches. For example, there
will probably be a neurodegenerative branch with sub-branches like Amyotrophic lateral
sclerosis (ALS) and Multiple Sclerosis (MS).
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