Study features

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Last updated: 19/04/2022

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.

Feature Types

The feature types available are listed in the Feature_Types table, listed below. In a data entry context each type would correspond to a single dropdown / option list, with all the associated value options being included in that list.

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

Feature Values

Within the database the available feature categories are all stored within a single table ('study_feature_categories'), and are distinguished there by a 'type' field, equivalent to the id of each type.
The available categories for each of the feature types are listed below. All are derived from the definitions given by ClinicalTrials.gov. N.B. The Ids assigned have no intrinsic meaning, and are largely a function of the order in which the categories were added. The assumption is that all would be used in the context of data entry, though 'not provided' could probably be omitted in most cases.

Phase

(interventional trials only)

id name description source
100 Not applicable 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 1/2 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 2/3 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 Not applicable For a single-arm trial. ClinicalTrials.gov
205 Randomised Participants are assigned to intervention groups by chance. ClinicalTrials.gov
210 Nonrandomised 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 assignment Clinical trials with a single arm. ClinicalTrials.gov
305 Parallel assignment Participants are assigned to one of two or more groups in parallel for the duration of the study. ClinicalTrials.gov
310 Crossover assignment 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 assignment Two or more interventions, each alone and in combination, are evaluated in parallel against a control group. ClinicalTrials.gov
320 Sequential assignment 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
450 Educational / counselling / training An intervention involving psychosocial or educational input. 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
502 Blinded (no details) From a statement that says the study was blinded, but where the degree of blinding was not provided WHO
505 Single ClinicalTrials.gov
510 Double ClinicalTrials.gov
515 Triple ClinicalTrials.gov
520 Quadruple ClinicalTrials.gov
599 Not applicable Explicitly labelled as not applicable - usually because the study is non-interventional WHO
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 study 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
640 Defined population ClinicalTrials.gov
645 Natural history 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
725 Retrospective / prospective ClinicalTrials.gov
730 Longitudinal 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