Table 4 Categories describing how RCHD was used to inform or supplement participant data

1

The RCHD alone is used as trial data, and there is no cross-checking or comparison against any other data.

One of the included RCTs was a cluster-randomised trial of GP practices. Outcome data specific to the trial were extracted at the level of the cluster (GP practice) from CPRD.

2

RCHD is used to cross-check against or verify known trial data, namely data already being collected on CRFs as part of the trial (arising from clinical observations and measurements).

In one case, death and cause of death of participants are captured on CRFs at each site. NHS Digital also sends the trial team quarterly reports of all new deaths. The trial team then compares the events and cause of death from both sources.

3

RCHD is used to cross-check against or verify self-reported trial data, namely data already being collected from participants, such as by questionnaire.

In one trial, participants are asked to complete a questionnaire every 3 months which asks whether they had any unexpected stays in hospital. This information is cross-checked against Hospital Episode Statistics data obtained from NHS Digital.

4

RCHD is used to alert or flag trial teams to a potential outcome/event, prompting medical note review to confirm the outcome/event. The specific outcome/events being flagged are not otherwise being captured as trial data. This may be accompanied by clinical end-point review or adjudication of events and outcomes.

In one RCT, participants were flagged in the UK Transplant Registry for notification of transplant rejection and failure. When participants were identified as having a transplant rejection or failure, study staff sought extra information from hospital records. The collated information was redacted and used for central adjudication by trained clinicians.

5

RCHD from one source is used to cross-check against or compared with RCHD from another source.

One of the included RCTs accessed RCHD from NHS Digital, ICNARC and OHCAO, and all had provided the same fields, such as length of stay in intensive care.

6

RCHD is being used for health economic analysis or cost-effectiveness purposes, rather than a clinical outcome.

In one study, Hospital Episode Statistics data were used to calculate the cost of secondary resource use within 90 days of randomisation.

7

RCHD is not used directly for trial purposes but to evaluate the quality of these data compared with trial data or other RCHD, or RCHD is used to generate an algorithm or equation that hopes to predict or replicate the frequency of events/outcomes.

In a breast cancer trial, cancer data from NCRAS were accessed and compared against the trial data to assess the completeness, validity and consistency of the two data sources.

Unclear

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