ALCOA-C, eSource and electronic data capture (EDC)

Data quality in human trials is not just a regulatory checkbox. It is what makes findings credible and defensible. The FDA and ICH GCP guidelines set out clear principles for what good data looks like. Those principles are summarised in the ALCOA-C framework, formalised in detail by the MHRA's GXP Data Integrity Guidance, which remains one of the most widely referenced regulatory documents on the subject and aligns closely with WHO and EMA definitions of the same principles.

It's worth treating ALCOA-C as a design specification rather than an audit checklist to satisfy retrospectively. A system built from the outset around these principles tends to produce them naturally, as a side effect of how it works. A system bolted together first and checked against ALCOA-C afterwards usually reveals gaps that are expensive to fix once the study is already running.

Attributable

Every data point must be traceable to its source: the individual who collected or entered it, when, and what changes were made since. In an EDC system, this means:

• Secure login with password and/or two-factor authentication
• Timestamps on every entry
• Edit logs that record what changed and who changed it

Legible

Electronic systems make this easier than paper. Defined fields, validated input types, and clear fonts eliminate the illegibility risk of handwritten records. The MHRA guidance is specific here too, clarifying that "legible" means permanent and understandable, not just readable at the moment of entry. The one area to watch is when paper records are later photographed or scanned for entry: transcription at that point introduces new risk and should be handled carefully.

Contemporaneous

Data should be recorded as close as possible to the time of observation, not filled in retrospectively at the end of a study. EDC systems support this through:

• Timestamps that record when an entry was made
• Time windows that restrict when data can be entered, preventing backdating

Original

The source is the first instance of data being recorded, whether that is a handwritten note or a direct entry into an electronic system. The original must be preserved, even if it is superseded by a correction. In EDC:

• Never overwrite original records
• Keep all versions with timestamps
• Use version numbers when appropriate

Accurate

Data must be correct. Errors should be identified and resolved promptly through documented corrections rather than silent edits. Field-level validation, data type restrictions, and the ability to make auditable amendments all support accuracy in EDC.

Complete

A complete dataset includes not just the data itself but the metadata surrounding it: who collected it, when, under what conditions, and with what supporting documents. This means:

• User access roles for everyone involved
• Defined and documented roles for all staff
• Training records for all system users
• Version-controlled supporting materials stored alongside the data they relate to

ALCOA+ terms: Consistent, Enduring, Available

Three additional principles extend the framework, and the MHRA's guidance treats these as equally binding rather than optional extras:

Consistent. Records should follow a common reference point (such as server timestamps) so that events can be traced in a logical sequence, particularly important in multi-site or multi-time-zone studies.

Enduring. Records need to be stored in formats that will remain accessible over time, with permanence being the specific standard the MHRA guidance calls out. Paper degrades. CDs fail. SSD storage with robust backup systems, including cloud backup, is more reliable for long-term archiving than any single physical medium.

Available. In high-risk studies especially, data must be accessible quickly when needed. This includes being able to produce human-readable exports without delay, and understanding exactly how your EDC system handles emergency unblinding or integration with electronic health records.

The full framework at a glance

Adhering to ALCOA-C, and the three additional ALCOA+ principles alongside it, provides a foundation for trustworthy findings. When the data is right, the claims that follow it are defensible. And in research, that is the whole point.