Most data queries are designed in, not entered in. Twelve practical rules for turning a protocol into case report forms that sites complete correctly the first time, with examples from real form builds.
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Medication name
CMTRTDose per administration
CMDOSEFrequency
CMDOSFRQStart date
CMSTDATOngoing?
CMONGOThe short version
Principles
An eCRF exists to collect the data the protocol requires, in a form the statistical analysis plan can use. That sounds obvious, but many forms are built by copying the previous study's forms and adding to them. The result is a casebook where sites fill in fields nobody analyses, and monitors verify data nobody needs.
A better starting point is the schedule of activities and the endpoints. For each assessment in the schedule, ask what data points the analysis needs, at which visits, in what units. Those become your fields. Anything else should earn its place: a safety reason, a regulatory requirement, or a clear operational use. The clinical trial protocol template shows how a well-structured protocol makes this mapping straightforward.
A field called "blood pressure" with a value of "120/80" is two measurements in one box, which means it cannot be range-checked or analysed without parsing. Split it into systolic and diastolic. The same applies to dose and unit, date and time, and anything a statistician will want to count separately.
Capture offers ten question types: short text, number, linear scale, slider, single choice, multiple choice, dropdown, date, time and long text, plus table sections for repeating rows. Use numbers for anything measured, single choice for mutually exclusive categories, multiple choice only when more than one answer can genuinely apply, and dates for dates. Keep long text for comments that nobody will analyse.
Put the unit in the field definition rather than asking sites to type it. If sites work in different units (pounds and kilograms, mg/dL and mmol/L), decide on one and convert at source, or add a unit selector and convert in analysis. Mixed units in one field are one of the most expensive problems to clean up.
CDASH, the CDISC standard for data collection, defines variable names and controlled terminology for common domains such as demographics, vital signs, adverse events and concomitant medications. Using CDASH-style names (AETERM, VSORRES, CMTRT) makes forms familiar to data managers and simplifies mapping to SDTM. Capture's templates carry an OID and an SDTM domain label on every form.
| Analyte | Result | Unit | Ref. range |
|---|---|---|---|
| Haemoglobin | 13.8 | g/dL | 13.0 to 17.0 |
| White blood cells | 6.2 | 10^9/L | 4.0 to 10.0 |
| Platelets | 412 | 10^9/L | 150 to 400 |
Choosing field types
| Data | Question type | Why | Example |
|---|---|---|---|
| Measured value | Number with fixed unit and decimals | Range checks and analysis without parsing | Weight 81.4 kg |
| Category, one answer | Single choice or dropdown | Coded values, no spelling variants | Sex, outcome of AE |
| Category, several answers | Multiple choice | Each option exported as its own flag | Seriousness criteria |
| Rating scale | Linear scale | Anchored, coded 0 to n | PHQ-9 items |
| Continuous self-rating | Slider with anchors | Visual analogue scales with no preset value | VAS pain 0 to 100 |
| Date | Date, partial dates allowed where needed | Consistent format, partial dates preserved | AE onset UNK-JUN-2026 |
| Clock time | Time | 24-hour, unambiguous | Bedtime 23:30 |
| Derived value | Calculated field | Never disagrees with its inputs | BMI, eGFR, QTcF |
| Repeating entries | Table section or log form | One row per event, own audit trail | Con meds, lab analytes |
| Free comment | Long text | Only where analysis does not need it | Investigator comment |
Form structure
Data collected at a scheduled visit (vital signs, questionnaires, physical exam) belongs on visit forms placed on the schedule. Data that happens on its own timeline (adverse events, concomitant medications, protocol deviations) belongs on log forms with repeating rows. Mixing the two, for example asking "any new AEs?" as a visit form question and then recording details elsewhere, creates duplicates and reconciliation work.
A form should cover one assessment. Separate forms can be scheduled independently, reused across studies, verified with different SDV settings and locked separately. A 200-field "Visit 3" form can do none of that.
If a follow-up question applies only to some answers, show it only for those answers. Conditional branching removes blank fields that monitors have to query ("was this left empty on purpose?") and keeps forms shorter for sites.
A blank field is ambiguous. Capture exports distinguish not done (ND), not available (NA), visit not done (VND) and not applicable from a genuinely missing answer, so data managers can tell an assessment that was skipped from one that was forgotten.
Medical history and adverse event onset dates are often known only to the month or year. Accepting partial dates such as UNK-JUN-2026 avoids invented days that later contradict source documents.
Stage 1
DraftBuild and edit freely
Stage 2
ApprovedLocked for live use
Stage 3
In the casebookOnly approved forms
SDV requirement changed on Systolic BP
Data manager · Reason: critical safety value
Form approved: Vital Signs (VS) v2
Study owner · Locked for live use
Answer changed: Weight 68.0 to 68.5 kg
Site coordinator · Reason: transcription error
Rule 9 and 10
Edit checks catch errors while they can still be fixed from memory. Range checks with a high and low limit, and custom-value rules with a priority, raise an auto-query in the site action list as soon as a value breaks the rule. Calculated fields such as BMI, body surface area, eGFR (CKD-EPI 2021), creatinine clearance, QTc (Bazett and Fridericia) and age from date of birth are shown read-only during entry, so they are never typed or mistyped.
Edit checks / auto-queries
2Type
Range High
Operator
Greater than
Value
180
Priority: High
Type
Range Low
Operator
Less than
Value
80
Priority: Normal
Query raised automatically
Value 192 violates limit (180). Please verify.
Rule 11
Nobody needs to type 40 lab analytes by hand. Capture's AI form builder drafts questions or a lab table from a description or an uploaded CSV, XLSX, PDF or DOCX, including units and reference ranges split by sex and age where the source has them. Nothing is saved until a person reviews and applies it, and it only works on draft forms, so the design decisions stay with you.
Question form
CRF or ePRO
Lab table
Analytes, units, ranges
1. Systolic blood pressure
Required · Number · mmHg · 0 dp
2. Diastolic blood pressure
Required · Number · mmHg · 0 dp
3. Pulse rate
Required · Number · beats/min
4. Body temperature
Required · Number · °C · 1 dp
5. Position during measurement
Required · Sitting, Supine, Standing
Build an eCRF in the free sandbox, enter test data that should fail your checks, and see what sites will see.
Rule 12: review before release
Forms move through a draft to approved lifecycle in Capture. Only approved forms appear in the casebook, and approved forms are locked for live use.
Build forms from the protocol, templates or AI drafts. Change anything while in draft.
Create test subjects and enter realistic and deliberately wrong data to exercise every check and branch.
Approve each form when it matches the protocol. Approved forms are locked and identical at every site.
Export the blank eCRF PDF (cover page, form index, visit-by-form matrix) for the ethics or IRB package.
Design review
Each field supports an endpoint, a safety requirement or a regulatory need.
One measurement or concept per field.
Defined on the field, not typed by sites.
AEs, con meds and deviations on logs with repeating rows.
Edit checks on the data that matters, not on every field.
Short instructions for anything a site could interpret two ways.
It collects only the data the protocol needs, uses question types that match the data, applies checks at entry, and is tested with realistic data before release.
The Clinical Data Acquisition Standards Harmonization standard from CDISC. It defines standard fields and names for common data collection domains, which simplifies later mapping to SDTM.
Use it as input, not as a template. Electronic forms can use skip logic, checks and calculated fields that paper cannot, so a direct copy misses most of the benefit. See paper CRF to eCRF conversion.
Enough to catch the errors that matter for safety and endpoints. Too many checks create query fatigue at sites without improving the data that drives the analysis.
Typically the data manager, a clinical representative, the statistician and someone from a site who will actually complete it.
AI can draft questions and lab tables from a description or file. People should still decide what the study collects and review every field before approval.
Usually a blank CRF. Capture exports a blank eCRF PDF with a cover page, form index, visit-by-form matrix and every approved form printed empty.
Keep exploring
eCRF templates
AE, demographics, vitals, eligibility and validated instruments.
CRF builder
Build forms with AI drafting.
What is a CRF?
Case report forms explained.
Edit checks software
Checks and auto-queries in depth.
Adverse event eCRF template
A log form done right.
Paper CRF to eCRF
Moving an existing study off paper.
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