Data integrity represents the fundamental requirement that clinical trial data accurately and completely represent the observations made during the trial and remain unaltered except through authorized, documented processes. The concept encompasses not merely the absence of errors but the assurance that data are attributable, legible, contemporaneous, original, and accurate throughout the entire data lifecycle from initial recording through analysis and archival.

The ALCOA principles provide a practical framework for evaluating data integrity. Attributable means that data can be traced to the person who generated it. Legible means that data can be read and understood. Contemporaneous means that data are recorded at the time the observation is made. Original means that data are the first recording (or a certified copy). Accurate means that data correctly represent the observation made. Some frameworks extend these principles to ALCOA+ by adding complete, consistent, enduring, and available.

Maintaining data integrity requires both procedural and technical controls. Procedural controls include training, supervision, documentation practices, and audit trails. Technical controls include system validation, access restrictions, backup procedures, and electronic signature requirements. The increasing use of electronic systems in clinical trials has introduced new considerations for data integrity, including requirements for system validation, audit trail functionality, and secure data transmission. Regardless of whether data are captured electronically or on paper, the sponsor and investigator share responsibility for ensuring that trial data are reliable and suitable for supporting regulatory decisions.