Before You Collect Your First Patient

Start with the row, not the spreadsheet

Before creating columns, decide what one row represents: a participant, a visit, an admission, or a specimen. A participant with four visits needs a structure that preserves those visits. Combining them into an unexplained summary can remove information the analysis needs.

Write the primary question in one sentence. Then define the outcome, its measurement window, and the comparison. “Complications” is not an operational definition. Specify the events included, the assessment period, and who determines whether an event occurred.

Pilot five fictional records

Use artificial examples that expose awkward cases: a missed visit, a repeated admission, an impossible value, an ambiguous category, and an outcome outside the planned window. Ask two team members to enter them independently. Differences in their entries identify unclear instructions before real collection starts.

These fictional records are for testing the form, never for reporting study results. A successful pilot does not validate a clinical measurement instrument.

Agree on a small set of rules

• Use a pseudonymous study identifier and keep any identifying key separately.
• State units and date formats explicitly.
• Give category codes a dictionary; do not rely on color or cell comments.
• Distinguish “not assessed,” “not applicable,” and “unknown” where the analysis needs that distinction.
• Never let a blank automatically mean zero or absence of disease.
• Record versions and explain changes to definitions.

Review the form alongside the planned result tables. If a table requires follow-up time or a denominator that the form cannot supply, resolve the mismatch now.

A practical next step

Build a draft dictionary with the Data Collection Builder, then use the Research Rehearsal service to scope an analysis dry run.

Download the collection pilot checklist.

Reporting guidance can help identify information that should be described, but does not replace study-design decisions: EQUATOR’s explanation of STROBE.