Electronic data capture (EDC) is the software in which each hospital in a clinical trial records what happened to each trial patient at each visit. It replaced the paper forms that trials used for decades. Each form in it is called an electronic case report form, or eCRF.
Before the trial starts, the trial's data team builds the forms. Each form follows the trial plan. A screening visit form might ask for age, weight, blood pressure and the results of a blood test. The team also writes rules for each field, called edit checks. An edit check is a test that the software runs on a value the moment it is typed.
Take, for example, a trial of a new blood-pressure tablet at a hospital in Lucknow. After a patient's week 4 visit, a research coordinator, the hospital employee who looks after the trial's paperwork, opens the patient's form. She types the weight as 650 kg, because she missed the decimal point. The form at once shows a warning: weight must be between 30 and 200 kg. She corrects it to 65.0 kg. Next, she leaves the blood pressure field empty. The form will not let her mark the visit complete until she fills it in or gives a reason.
Some errors cannot be caught by a rule. So a monitor from the contract research organisation (CRO) later compares the form with the hospital's own records, such as the hospital EHR. If the two differ, the monitor raises a query, a question attached to that field. The coordinator answers it or corrects the value. Every change keeps the old value, the new value, who changed it, when and why. This record of changes is called an audit trail, and GxP rules require it.
EDC holds what the hospital records. It does not hold everything. Questionnaires that patients fill in themselves are collected by eCOA. Each patient's treatment group is held by RTSM software, and EDC only shows a pack number. All these sources are combined later in the clinical trial data platform.
Some newer trials copy values straight from the hospital's records into EDC, instead of typing them twice. This saves time and removes copying errors. EDC data can also be compared with a synthetic control arm, a comparison group built from earlier patients' records instead of newly enrolled ones.