Stratification

Oracle Clinical provides stratification utilities to ensure that the groups you select are mutually exclusive and represent a full cross-section of your study's population. For example, you could stratify a study according to the following groups:

male smokers over 65

male nonsmokers over 65

males 40 to 65

female smokers 45 to 65

females over 65

You create strata with a view to preserving statistical significance. For example, superficially the following two examples of stratification for a study seem to be the same. However, these stratification patterns impose different constraints on randomization.

• two strata: male smokers; male nonsmokers and women

• three strata: male smokers; male nonsmokers; women

The first could result in a randomization where 100 patient positions include male smokers, but 200 other patient positions include either male nonsmokers or females.

The second stratification pattern could result in a randomization where 100 patient positions include male smokers, and 200 include male nonsmokers and females. Both stratifications could be useful, but each would have a different statistical significance.

For more information, see:

• Maintaining Factors
  
• Maintaining Single Strata
  
• Maintaining Combination Strata and Combined Combination Strata
  
• Maintaining a Study Stratification Factor
  

Maintaining Factors

As a first step in creating strata, clinical study enrollment criteria, clinical study termination criteria, and treatment regimens, you create factors. Factors are attributes of a patient you can measure, rather than the actual values of attributes in individual cases.

To reach the Maintain Factors window, from the Design menu, select Strata, then select Factors.

For more information, see:

• Glossary of Terms for Factors
  

Glossary of Terms for Factors

Ranges represent variables requiring further qualification to make them meaningful to the study. Examples are AGE, WEIGHT, and BLOOD PRESSURE, which require maximum and minimum values to specify their roles in the study.

Values, on the other hand, are variables such as BLOOD GROUP, which require only a single value to make them meaningful.

The Range/Value box in the Factors window designates a variable as either a range or a value. You can change the flag only if the factor is not used by any clinical study enrollment criteria, clinical study termination criteria, treatment regimen, or strata; otherwise you get an error message.

A retired factor can still relate to existing strata, but cannot be used to create a new stratum. A retired factor can be reactivated by setting the Active? box back to selected.

You can delete a factor only if it is not being used by any strata, clinical study enrollment criteria, clinical study termination criteria, or treatment regimen. You get an error message if you try to delete a factor that is in use. For a factor, define a code, description, either a value or range, and whether it is available for assignment to strata. You must create all of the factors needed to compose each stratum.

Maintaining Single Strata

To create, modify, and delete single strata, created for use in all clinical studies, use the Maintain Single Strata window.

To access this window, from the Design menu, select Strata, then Single Strata; this initially displays the Factors window.

For more information, see:

• Selecting a Factor
  
• Selecting a Stratum
  

Selecting a Factor

You select a factor from the Factors window list of all active factors before you can proceed to create a single stratum. This is the factor for which you create or update the single stratum.

You cannot insert, update, or delete factors from this window. You can only select a factor for which to create a single stratum

Selecting a Stratum

The Strata button in the Factors window of the Maintain Single Strata window displays the Strata window. Here you can create, update, or delete single strata for the factor you selected in the Factors window.

A new stratum can only be created for an active factor.

You can delete a single stratum only if it is not used in any combined strata or combined combination strata, and if no study stratification factors assign it to a clinical study version. To delete the stratum, select Delete Record.

The minimum/maximum values and the single value are mutually exclusive: if your factor is of type RANGE, you must enter minimum and maximum values; if the factor is of type VALUE, you must enter a single value. Select a factor to define single strata. You can create the factor records by selecting Strata from the Design menu, and choosing Factors. Then click the Strata button.

Maintaining Combination Strata and Combined Combination Strata

You link single strata to create combination strata, logically linked by AND, or combined combination strata, logically linked by OR.

To link single strata with an AND statement, open the Maintain Combination Strata window: from the Design menu, select Strata, then choose Combination Strata.

To link single strata with an OR statement, open the Maintain Combination Strata window: from the Design menu, select Strata, then choose Combined Comb Strata.

Because the two modules operate identically in every other respect, the following instructions apply to both modules.

Each window has one field, Description, which is required and must be unique. Enter a description of the stratum, indicating the presence of AND or OR logic.

The forms for maintaining Combination Strata and Combined Combination Strata each have an associated Available Factors window and a Strata for Factor window, reached by pressing the Factor or Strata button, respectively. These windows allow you to change the selected Combination or Combined Combination Stratum by adding or removing constituent (strata).

For more information, see:

• Assigning Strata to Combination or Combined Combination Strata
  
• Displaying Strata Assigned to Combination or Combined Combination Strata
  

Assigning Strata to Combination or Combined Combination Strata

Select a factor and then click Strata to see the strata assigned to the factor. This window displays the strata for the factor selected earlier. Click the Add or Remove button to create the set of strata in the strata you are creating.

The following buttons appear in the Strata for Factor window. Add or remove special factor-related strata to the selected combination stratum with these buttons:

• Add assigns the selected stratum to the strata.

• Remove removes the selected stratum.

Displaying Strata Assigned to Combination or Combined Combination Strata

Use this function to display the strata already assigned to a combination strata or combined combination strata and allow them to be removed.

Maintaining a Study Stratification Factor

The assignment of a stratum to a clinical study version is a study stratification factor. To create and maintain study stratification factors, see:

• Selecting a Clinical Study Version
  
• Maintaining Strata
  

Selecting a Clinical Study Version

To assign a stratum to a clinical study version, navigate to Design, Strata, then Stratification. Select a clinical study version to work with from the list. The system selects the most recently accessed clinical study version during the current session. If you have not selected a study, the window displays all existing clinical study versions.

Maintaining Strata

To reach the Study Factors window, which lists the strata assigned to the study, navigate to Design, Strata, Stratification, and click the Stratum Assigned to the Study button. Stratum Description is the lone field for this window. It is a display-only description of the stratum that the factor is for.

Two function-specific buttons appear in the Study Stratification Factors window:

• Factors displays the Factors window. Assign one or more of the associated strata to your study.

• Details of the Stratum displays the Strata window in single-record format. You can also reach the Strata window from the Factors window, via the Strata window. Select a stratum to work with while in this window.

The following buttons are in the Strata window:

• Details of the Stratum displays the window Details of Selected Stratum. It shows the details of a stratum assigned to a study or of a stratum for a factor before assignment to a study.

• Assign Stratum to Clinical Study enables you to add a stratum to the list of assigned strata.