- Trial elements are the building blocks of arms. Arms consisting of elements are the paths that subjects will follow throughout a trial. All elements are related to study treatment. Therefore, an element is defined by the treatment (or lack of treatment) to be administered to subjects during the element, as well as either the planned duration or start/end rules of the element.
- Elements with different start and end rules are different elements and must be represented as unique values in ELEMENT and ETCD (i.e., elements involving the same treatment but different durations are different elements). The same applies to nontreatment elements (e.g., a wash-out with a fixed duration of 14 days is different from a wash-out that ends after 7 days if drug cannot be detected in a blood sample or after 14 days if drug can be detected in a blood sample).
- ELEMENT and ETCD values in TE, Subject Elements (SE), and Trial Arms (TA) must coincide (ELEMENT and ETCD are defined as the planned trial elements in TE, and the planned elements are then applied to subjects in SE and to arms in TA).
- Additional factors beyond treatment, start rule, and either end rule or duration do not distinguish separate elements. For example, a restricted vs. ad libitum diet for the same treatment does not necessarily imply different treatment elements for the subjects experiencing these conditions, even though the subjects may be analyzed differently or be assigned to different groups or trial sets.
- Elements often appear in more than one arm or epoch and can be reused within the same arm or epoch and across arms and epochs. Therefore, it is not recommended that the values of ETCD and ELEMENT refer to arms or epochs.
- There are no gaps between elements. The instant one element ends, the next element begins. A subject spends no time "between" elements.
- The ELEMENT variable contains the description of the element and often indicates the treatment being administered during an element. If no treatment is administered, as is often the case with a screening element, the other activities that define this period of time (as related to a treatment element) become the value of ELEMENT (e.g., "Screening," "Recovery," "Washout," where screening, recovery, and wash-out all take place within the context of the treatment element).
- For treatment elements, the ELEMENT variable may include the following information (if appropriate for the element): treatment amount; treatment frequency; and total daily dose, if different from treatment amount.
- TESTRL is the rule that defines the start of element. TESTRL identifies the event that marks the transition into an element. For elements that involve treatment, TESTRL is usually populated with a value that indicates treatment administration.
- The start of the study for a particular arm is defined by the value of TESTRL for the first element within that arm.
- TESTRL for a treatment element may be thought of as active while the start rule for a nontreatment element, particularly a recovery or wash-out element, may be passive. The start of a treatment element will not occur until a dose is given, no matter how long that dose is delayed. Note that the date/time of the event that starts an element, which is described in TESTRL, will be used to populate the SESTDTC date/times in the SE dataset. Therefore, TESTRL should refer to an event of that the date/time will be captured during the course of the study.
- TESTRL and TEENRL should be expressed without referring to arm or epoch.
- TEENRL describes the circumstances under which an element ends, causing subjects to enter into another element. Element end rules may depend on a variety of conditions. The TA dataset, not the TE dataset, describes where the subject moves next; therefore, TEENRL values must be expressed independently of arms.
- For elements that do not involve treatment, TESTRL can be more difficult to define. For wash-out and recovery elements, which often follow treatment elements, the start of the element may be defined relative to the end of a preceding treatment. For example, a wash-out period might be defined as starting after the last dose of drug for the preceding treatment element. This type of definition will place constraints on how the element can be sequenced within the TA dataset.
- Defining a clear starting point for the start of a nontreatment element that always follows another nontreatment element can be particularly difficult. The transition may be defined by a decision-making activity such as randomization. For example, every arm of a study that involves treating disease episodes might start with a screening element followed by an element that consists of waiting until a disease episode occurs after an initial randomization of subjects. The activity that marks the beginning of the wait element might then be the randomization.
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