Source document verification represents a fundamental quality control activity in clinical trials, ensuring that data entered into case report forms accurately reflects the original observations and measurements recorded in source documents. Through direct comparison of CRF entries against medical records, laboratory reports, and other source materials, monitors can identify transcription errors, data entry mistakes, and inconsistencies that might otherwise compromise data integrity.

The extent and approach to SDV has evolved significantly with the adoption of risk-based monitoring principles. Traditional monitoring practices often emphasized 100% SDV of all data points, requiring monitors to verify every entry against source documents during on-site visits. Current guidance, reflected in ICH E6(R3), recognizes that this approach may not be the most efficient use of monitoring resources and may not effectively identify critical issues that affect participant safety or trial endpoints.

Risk-based approaches to SDV focus verification activities on data most critical to participant safety and the primary endpoints of the trial. Statistical sampling techniques may be used to assess overall data quality without reviewing every data point. Centralized monitoring activities can identify sites or participants with unusual data patterns warranting focused review. This evolution does not diminish the importance of data accuracy but rather applies resources more strategically to ensure that verification activities address the most significant risks to trial integrity.