. 2019 May 29;20:294. doi: 10.1186/s13063-019-3322-7

Table 4.

Advantages and challenges of generic and comparison-specific case report forms

CRF type	Generic	Comparison-specific
Advantages	• Efficient if data requirements are similar across comparisons • Data are captured consistently across comparisons • Capacity to still make sections specific by arm, comparison, sites, patient sub-group, etc. • CRF changes need to be made on only one set of CRFs, reducing time taken for development/amendments • Generally fewer CRFs overall	• Efficient if data requirements are substantially different across comparisons • Only data required for a single comparison is captured • Not likely to become as complex as generic CRFs. May therefore be easier for site staff to use. • Each CRF is easier to maintain for comparison-specific changes • Not all changes across life of the trial must be included, only those during the lifespan of the CRF
Challenges	• Adding comparisons/questions. - Increasing length and complexity as additional data requirements are added - Question numbering can become unwieldy if new questions are needed within the existing CRF - Unanticipated changes may require existing CRF to be redeveloped or a new CRF to be developed^a - Shared control arm participants may be affected by new comparisons requiring conditional questions/sections to be added^b • Less flexibility in collecting data - Must ensure CRFs can be relevant for all comparisons • Changes external to the trial may be more likely to impact generic CRFs^c - Universal coding lists changing the names or values of items on the list^d - Changes in standard of care	• Generic changes will need to be made across specific CRFs separately, increasing maintenance time and risk of errors. • More CRFs in total - Can take longer to train site staff on each individual CRF if they are different from each other - Version control/CRF tracking. Multiple similar versions with differing version numbers. Data management staff must be more careful to ensure correct version is used. • If a shared control arm is being used, CRFs for this arm must still capture data required for multiple comparisons whilst ensuring this does not introduce bias; additional questions may lead to events being more likely to be reported or introduce other biases. Some questions may need to be added to all comparison-specific CRFs to avoid this.

CRF type

Generic

Comparison-specific

Advantages

• Efficient if data requirements are similar across comparisons

• Data are captured consistently across comparisons

• Capacity to still make sections specific by arm, comparison, sites, patient sub-group, etc.

• CRF changes need to be made on only one set of CRFs, reducing time taken for development/amendments

• Generally fewer CRFs overall

• Efficient if data requirements are substantially different across comparisons

• Only data required for a single comparison is captured

• Not likely to become as complex as generic CRFs. May therefore be easier for site staff to use.

• Each CRF is easier to maintain for comparison-specific changes

• Not all changes across life of the trial must be included, only those during the lifespan of the CRF

Challenges

• Adding comparisons/questions.

- Increasing length and complexity as additional data requirements are added

- Question numbering can become unwieldy if new questions are needed within the existing CRF

- Unanticipated changes may require existing CRF to be redeveloped or a new CRF to be developed^a

- Shared control arm participants may be affected by new comparisons requiring conditional questions/sections to be added^b

• Less flexibility in collecting data

- Must ensure CRFs can be relevant for all comparisons

• Changes external to the trial may be more likely to impact generic CRFs^c

- Universal coding lists changing the names or values of items on the list^d

- Changes in standard of care

• Generic changes will need to be made across specific CRFs separately, increasing maintenance time and risk of errors.

• More CRFs in total

- Can take longer to train site staff on each individual CRF if they are different from each other

- Version control/CRF tracking. Multiple similar versions with differing version numbers. Data management staff must be more careful to ensure correct version is used.

• If a shared control arm is being used, CRFs for this arm must still capture data required for multiple comparisons whilst ensuring this does not introduce bias; additional questions may lead to events being more likely to be reported or introduce other biases. Some questions may need to be added to all comparison-specific CRFs to avoid this.

CRF Case report form

^aSee practical examples from STAMPEDE CRF amendments

^bEasier to accomplish in electronic data capture with conditional formatting in the study database

^cCould still be a challenge for comparison-specific CRFs

^dE.g. Common Terminology Criteria for Adverse Events (CTCAE) update V3.0 to V4.0