Study features

Study features refers to categorised aspects of study design, such as phase or intervention model.These are important as the basis of filters that can be applied to study lists.
The feature types available are listed in the Feature_Types table, listed below:

Feature Types

id	name	description	source
20	Phase	For a clinical trial of a drug product (including a biological product), the numerical phase of the clinical trial.	ClinicalTrials.gov
21	Primary purpose		ClinicalTrials.gov
22	Allocation type	The method by which participants are assigned to arms in a clinical trial.	ClinicalTrials.gov
23	Intervention model	The strategy for assigning interventions to participants.	ClinicalTrials.gov
24	Masking	The party or parties involved in the clinical trial who are prevented from having knowledge of the interventions assigned to individual participants.	ClinicalTrials.gov
30	Observational model	The Primary strategy for participant identification and follow-up.	ClinicalTrials.gov
31	Time perspective	For observational studies, describes the temporal relationship of observation period to time of participant enrollment.	ClinicalTrials.gov
32	Biospecimens retained	Indicates whether samples of material from research participants are retained in a biorepository.'	ClinicalTrials.gov

Within the database they are all stored within a single table ('study_feature_categories'), and are distinguished there by a 'type' field, equivalent to the heading of each table.
The integer ids are keys within the table but are not used elsewhere in the mdr.
The available categories for each of these is listed below. All are derived from the definitions given by ClinicalTrials.gov.

Phase

(interventional trials only)

id	name	description	source
100	N/A	Trials without phases (for example, studies of devices or behavioural interventions).	ClinicalTrials.gov
105	Early Phase 1	Exploratory trials, involving very limited human exposure, with no therapeutic or diagnostic intent (e.g., screening studies, microdose studies).	ClinicalTrials.gov
110	Phase 1	Initial studies to determine the metabolism and pharmacologic actions of drugs in humans, side effects, and to gain early evidence of effectiveness; may include healthy participants and/or patients.	ClinicalTrials.gov
115	Phase 1/Phase 2	Trials that are a combination of phases 1 and 2.	ClinicalTrials.gov
120	Phase 2	Controlled clinical studies conducted to evaluate the effectiveness of the intervention for a particular indication in participants with the disease or condition under study, and to determine the common short-term side effects and risks.	ClinicalTrials.gov
125	Phase 2/Phase 3	Trials that are a combination of phases 2 and 3.	ClinicalTrials.gov
130	Phase 3	Trials conducted after preliminary evidence suggesting effectiveness of the drug has been obtained, and are intended to gather additional information to evaluate the overall benefit-risk relationship of the drug.	ClinicalTrials.gov
135	Phase 4	Studies of approved drugs to delineate additional information including the drug's risks, benefits, and optimal use.	ClinicalTrials.gov
140	Not provided	No data was provided in the source record.	ECRIN

Allocation type

(interventional trials only)

id	name	description	source
200	N/A	For a single-arm trial.	ClinicalTrials.gov
205	Randomized	Participants are assigned to intervention groups by chance.	ClinicalTrials.gov
210	Nonrandomized	Participants are expressly assigned to intervention groups through a non-random method, such as physician choice.	ClinicalTrials.gov
215	Not provided	No data was provided in the source record.	ECRIN

===Intervention model=== (interventional trials only)

id	name	description	source
300	Single Group	Clinical trials with a single arm.	ClinicalTrials.gov
305	Parallel	Participants are assigned to one of two or more groups in parallel for the duration of the study.	ClinicalTrials.gov
310	Crossover	Participants receive one of two (or more) alternative interventions during the initial phase of the study and receive the other intervention during the second phase of the study.	ClinicalTrials.gov
315	Factorial	Two or more interventions, each alone and in combination, are evaluated in parallel against a control group.	ClinicalTrials.gov
320	Sequential	Groups of participants are assigned to receive interventions based on prior milestones being reached in the study, such as in some dose escalation and adaptive design studies.	ClinicalTrials.gov
325	Not provided	No data was provided in the source record.	ECRIN

Primary purpose

(interventional trials only)

id	name	description	source
400	Treatment	One or more interventions are being evaluated for treating a disease, syndrome, or condition.	ClinicalTrials.gov
405	Prevention	One or more interventions are being assessed for preventing the development of a specific disease or health condition.	ClinicalTrials.gov
410	Diagnostic	One or more interventions are being evaluated for identifying a disease or health condition.	ClinicalTrials.gov
415	Supportive Care	One or more interventions are evaluated for maximizing comfort, minimizing side effects, or mitigating against a decline in the participant's health or function.	ClinicalTrials.gov
420	Screening	One or more interventions are assessed or examined for identifying a condition, or risk factors for a condition, in people who are not yet known to have the condition or risk factor.	ClinicalTrials.gov
425	Health Services Research	One or more interventions for evaluating the delivery, processes, management, organization, or financing of healthcare.	ClinicalTrials.gov
430	Basic Science	One or more interventions for examining the basic mechanism of action (for example, physiology or biomechanics of an intervention).	ClinicalTrials.gov
435	Device Feasibility	An intervention of a device product is being evaluated in a small clinical trial (generally fewer than 10 participants) to determine the feasibility of the product, or a clinical trial to test a prototype device for feasibility and not health outcomes.	ClinicalTrials.gov
440	Other	None of the other options applies.	ClinicalTrials.gov
445	Not provided	No data was provided in the source record.	ECRIN

Masking

(interventional trials only)

id	name	description	source
500	None (Open Label)		ClinicalTrials.gov
505	Single		ClinicalTrials.gov
510	Double		ClinicalTrials.gov
515	Triple		ClinicalTrials.gov
520	Quadruple		ClinicalTrials.gov
525	Not provided	No data was provided in the source record.	ECRIN

Observational model

(observational studies only)

id	name	description	source
600	Cohort	Group of individuals, initially defined and composed, with common characteristics (for example, condition, birth year), who are examined or traced over a given time period.	ClinicalTrials.gov
605	Case-Control	Group of individuals with specific characteristics (for example, conditions or exposures) compared to group(s) with different characteristics, but otherwise similar.	ClinicalTrials.gov
610	Case-Only	Single group of individuals with specific characteristics.	ClinicalTrials.gov
615	Case-Crossover	Characteristics of case immediately prior to disease onset (sometimes called the hazard period) compared to characteristics of same case at a prior time (that is, control period).	ClinicalTrials.gov
620	Ecologic or Community Studies	Geographically defined populations, such as countries or regions within a country, compared on a variety of environmental (for example, air pollution intensity, hours of sunlight) and/or global measures not reducible to individual level characteristics (for example, healthcare system, laws or policies median income, average fat intake, disease rate).	ClinicalTrials.gov
625	Family-Based	Studies conducted among family members, such as genetic studies within families or twin studies and studies of family environment.	ClinicalTrials.gov
630	Other	Explain in Detailed Description.	ClinicalTrials.gov
635	Not provided	No data was provided in the source record.	ECRIN

Time perspective

(observational studies only)

id	name	description	source
700	Retrospective	Look back using observations collected predominantly prior to subject selection and enrolment.	ClinicalTrials.gov
705	Prospective	Look forward using periodic observations collected predominantly following subject enrolment.	ClinicalTrials.gov
710	Cross-sectional	Observations or measurements made at a single point in time, usually at subject enrolment.	ClinicalTrials.gov
715	Other	Explain in Detailed Description.	ClinicalTrials.gov
720	Not provided	No data was provided in the source record.	ECRIN

Biospecimens retained

(observational studies only)

id	name	description	source
800	None Retained		ClinicalTrials.gov
805	Samples With DNA		ClinicalTrials.gov
810	Samples Without DNA		ClinicalTrials.gov
815	Not provided	No data was provided in the source record.	ECRIN