Source documents constitute the original records where clinical trial data are first recorded, serving as the foundational evidence that supports all data entered into case report forms and included in regulatory submissions. The integrity of clinical trial data ultimately depends on the quality, completeness, and accessibility of source documents, which must enable reconstruction and evaluation of the trial if required by regulatory authorities.

The range of documents that may serve as source data is extensive and depends on the specific assessments and procedures conducted in the trial. Hospital records, physician office charts, laboratory printouts, imaging reports, ECG tracings, pharmacy dispensing records, and patient-completed diaries all represent common source documents. Electronic health records increasingly serve as source documents, requiring attention to system validation, access controls, and audit trail functionality to maintain data integrity.

Source documents must be attributable, legible, contemporaneous, original, and accurate, often summarized by the acronym ALCOA. These attributes ensure that the data can be traced to its origin, read and understood, recorded at the time of the observation, represent the original recording rather than a copy, and accurately reflect the observation or measurement made. Any corrections to source documents must be made in a manner that preserves the original entry, typically by drawing a single line through the error, entering the correction, providing an explanation, and including the date and initials of the person making the correction.