The basic unit of information in the PKS is a study. A study starts with a collection of raw data that must include longitudinal observations, observation times and subject identifiers, and may include dosing and subject demographics. A study must have these data characteristics if data is mapped to PKS internal structures, but the study can contain any type of data if stored in the study library. Studies can be created with data mapped to the PKS data structures, or they can contain file-based data, maintained in the study library. As analyses are performed on these data, the analyses, including model settings and results, can be added as scenario(s) within the study.
A PKS study requires specific fields. First, a study must include at least one column containing subject identifiers. A collection of fields taken together can be used for subject identification. For example, first name, last name.
A study can include, but is not required to have, multiple columns of subject data: time-invariant, subject-specific information such as body weight or gender, that is, baseline covariates.
A study can include time-dependent observation and dosing data. Observation data can include records of concentration, measurements of blood pressure, heart rate, etc. Each data collection point can have multiple observations. In this case, a sampling variable is used to differentiate the samples.
If the observation data includes multiple, concurrent measurements for any subject, for example, multiple assays performed on a given sample or multiple samples during a given visit, the dataset must include a variable that differentiates the measurements, that is, values 1, 2, 3 for the 1st, 2nd, and 3rd samples.
Because a study can include time-dependent observation data, a study must include relative nominal time, indicating the times at which observations and doses, if included, were scheduled in the protocol. This contrasts with relative actual time, representing the times that observations or doses really happened. Relative time is time elapsed since the start of the study, period, or phase. If the data uses infusion dosing, the relative nominal end time must be identified as well. If only the Relative Nominal Time is defined in the dataset, a duplicate column is created for the actual times.
Note: To create a study that does include longitudinal observation data, include a dummy time column, with values for each row as placeholders, in the study.
Valid relative time units in PKS are sec, min, hr, day, weeks, years. This restriction only applies to the nominal time, nominal end time, relative time, and relative end time. Other data elements can have any units (times, concentrations, or other measurements).
When a study is created, information about the study can be entered in the Create Study dialog. This dialog includes information about the study: Study Name, Portfolio, Project, Indication, Study Type, Study Design, Compound, etc. The metadata provides ways to search and filter the data within the database. The metadata are saved with the study. See “Creating a PKS study” for more information about study metadata.
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