One such practice is commonly referred to as "The Parking Lot Syndrome," in which subjects sit in their cars prior to site visits and complete two weeks worth of diaries, trying to recall how they felt days ago. When subjects fail to record data close to the time of the event they are describing—whether it's noting how they slept, recording what they ate, or writing down where it hurt and how they reacted to medication—they often discover that such details are as forgettable as last Tuesday's lunch. Faced with an empty paper diary and a deadline, subjects struggle to remember what they did a few days ago. In some cases, they leave the diary blank or only record what they remember. In the worst case, they make up entries.

Electronic patient diaries help make self-reported patient data much more reliable for companies seeking FDA approval of new therapies or medical devices that include patient-reported outcomes.

Not only do electronic patient-reported outcome (ePRO) solutions enable trial sponsors to enforce recording deadlines and encourage prompt compliance, but they also help keep subjects honest. When patients are issued electronic diaries—typically a personal digital assistant (PDA) with specialized software designed exclusively for the trial—the sponsor dictates the time frame during which patients can record data. For example, if the sponsor decides that the morning diary will be available only between the hours of 6 and 9 a.m. to record sleep data, subjects have only that three-hour window to record their entry. If they forget, there is no entry for that morning.

Of course, the PDA can be programmed to help patients remember to record their data. It might buzz to inform subjects that a recording period has begun, or beep to remind them that they have 30 minutes left to make an entry. The sponsor can choose these functions and program them into the study design. At one time of day, only the window for recording sleep data will open. Hours later, that window is closed, but patients can record medication reactions, diet, or physical activity. At the end of the day, data collected on the PDA is transmitted by the subject, through wireless or analog telecommunications, to a central server hosted by the ePRO solution provider. Clinical sites, monitors and sponsors can then review the patient-reported data in real time online. This enables faster decisions and proactive trial management based on up-to-date knowledge of patient diary compliance, key patient data reports, and enrollment. Sites, monitors and sponsors have to wait days or even weeks for double-data entry, reconciliation, and source verification processes associated with paper diaries before they can access the data. If a few days go by without an entry, the site coordinator can call the subject to make sure he or she is using the eDiary properly. With paper diaries, a trial can be nearly over before compliance problems surface.