How to design an effective electronic CRF

Why CRF design matters

An electronic Case Report Form (eCRF) is not a dressed-up Google Form. It's the primary collection instrument, and poor design multiplies queries, delays database lock, and compromises analytic integrity.

Three core principles

• Align with the protocol: every variable must exist in the protocol and support an outcome. If not, cut it.
• Minimize free text: open fields are the fast lane to dirty data. Use selects, scales, or calculated fields whenever possible.
• Respect the real clinical flow: order questions as the clinician will capture them, not as they appear in the protocol.

10 practical rules

1. One field, one datum. Never combine "randomization date + time" in a free input.
2. Use correct field types. Dates with date picker, numbers with range validation.
3. Apply validations at entry time, not at lock. Zod, yup, whatever — inline.
4. Use conditional logic. Hide irrelevant questions.
5. Mark required vs. optional explicitly. But don't require everything.
6. Always include an explicit "not applicable". Empty ≠ N/A.
7. Use consistent, documented units (kg vs lbs, mmol/L vs mg/dL).
8. For validated scales, respect original scoring. Don't reinvent CTCAE or SF-36.
9. Group sections with clear headers.
10. Preview on mobile. Half of collection will happen on a tablet.

Audit trail and versioning

Any eCRF claiming 21 CFR Part 11 or ICH-GCP compliance must be versioned with full audit trail. Any change after publish creates a new version; already collected records keep their original version link.

Trialinx applies this by default — you cannot edit a published form, only create a new version.

Conclusion

The CRF is your instrument. Treat it with the same care a pulmonologist treats a spirometer. Five extra hours of design save weeks of queries at the end of the trial.