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Choosing the Right System for your Clinical Trial: Understanding the Differences between EDC and IVR/IWR

Posted by Jamie Hahn on Tue, Apr 09, 2013 @ 09:05 AM


headshot steve palmatierThe following article was contributed by Steve Palmatier, Rho's service leader for Interactive Response Technology (IxR) system configuration and development.

Sometimes it's difficult to determine the best tool for a job, especially when technologies are developed in parallel to handle similar tasks.  Take Interactive Response Technology (IxR) and Electronic Data Capture / Electronic Case Report Forms (EDC), for example.  Both technologies provide a method for electronic entry of important data.  Both can have data verification checks incorporated to minimize the potential for ambiguous or incorrect data entry.  Both commonly incorporate user roles to limit access of individual users to functionality that is appropriate.  So what are the differences that would provide insight on which technology to use when?  Several areas of differentiation are outlined below.

Purpose of the System

EDC - In short, EDC systems’ primary purpose is to electronically collect and validate participant data for eventual use in statistical analyses.  Collecting these data electronically makes them more quickly available to the study team than traditional paper CRFs, and therefore allows more informed and proactive decision making.

IxR – The goal of IxR in clinical trials is to perform specific tasks, such as randomization, study drug dispensation, study drug resupply requests, emergency unmasking, etc.  It is not the goal of IxR in most cases to be the primary place where participant data are entered and stored, though some data are required to perform the aforementioned tasks.

System Interface

EDC – Due to the sheer volume of data to be captured, EDC systems nearly always use a computer-based interface that allows users to easily navigate between forms and between different areas on the same form.  While swift entry of data into EDC systems is often desired so that study teams have accurate enrollment information, it is not usually operationally critical, so it is acceptable for a user to enter data in not-quite-real-time.  Moreover, most clinical sites in developed countries can be expected to have computers, so a computerized interface is acceptable the vast majority of the time.

IxR – IxR has two main interfaces: web and voice (IWR and IVR respectively).  Over the past 10 years or so, the prevalence of IVR systems has decreased significantly due to workstations, laptops, smartphones, and tablets becoming more widely available in the clinical setting.  However, there are still some instances in which the phone interface is beneficial, such as when entry of data for randomization is highly time-sensitive (e.g., in neonatal trials where randomization must occur very shortly after birth), and when the IxR will be used for patient-reported outcomes or diary entry, since study subjects may not have access to a computer at home.

Navigation Paradigm

EDC - Most EDC systems are form-based, and most of the data entry fields on any particular web page are static.  When a participant is enrolled in a trial, a set of forms is made available into which that participant’s data will be entered.  Whether these forms are necessary or not becomes apparent later.  For instance, if a participant withdraws consent early in the study, there may be many forms for visits later in the study that never have data associated with them.  In many cases, the order in which data are entered is not controlled since different data will become available at different times, though sometimes additional forms are generated as they become necessary (e.g., SAE forms).

IxR - IxR systems generally create data entry pages dynamically.  That is, the information and entry fields that appear on-screen or that are prompted over the phone are a result of previous selections and entries made by the user.   This both minimizes data entry by the user and provides a gating mechanism that forces things to happen in the correct order.  For instance, a user cannot skip to kit assignment prior to randomization, or randomization prior to entry of valid stratification data.

User Modification of Previously Entered Data

EDC - EDC forms can usually be revisited multiple times because all of the data that are to be entered on a form may not be available at once (e.g., lab values).  Often, entry of data that seems inaccurate or is in an incorrect format is accepted and stored but fires a query that must be resolved prior to database lock, and the user may return at a later time to correct or confirm the entry.  This is consistent with the primary purpose of EDC, to store data for use in data analysis that will take place at a later date.

IxR - Unlike EDC forms, entry of data and completion of a function in IxR usually triggers an action that is based on the entered data, so it is uncommon for a user to be able to return to the system to make corrections of previously missing or incorrectly entered data without support intervention.     Incorrect entry of stratification data prior to randomization has cascading impacts, so correcting the mistake often involves more than simply updating that one data point.

Validation Burden

EDC – Because there is an opportunity to correct mistakes between the initial entry and database lock, the importance of correct and complete data at the time of entry is not often assessed to be at the highest level.  Also, since the primary purpose of EDC is to store data rather than to perform actions, validation of the system can focus primarily on making sure that edit checks fire correctly and that the data is stored accurately.

IxR - Because IxR performs actions that impact the course of the study, IxR systems generally carry a higher risk than EDC systems.  Not only is it important for validation efforts to ensure that the entered data is correct; but it is also important to validate the logic that is exercised in order to make the decisions and perform the actions that are based on that data – assigning the correct treatment kits, requesting resupply of investigational product when appropriate, enforcing cohort caps, etc.  The result is that IxR systems (especially those that are highly configurable) generally require more extensive validation and a higher percentage of setup time allotted to validation activities.

In the next post in this series, we’ll use these distinctions to help determine the appropriate scope for IxR systems so that the technology can be used most advantageously.

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