gms | German Medical Science

Background: Randomized controlled trials (RCTs) are the only way to ensure internal validity. However RCTs are usually expensive. Moreover the lack of external validity is often criticized.

Registries enable rapid recruitment of patients and cost-effective acquisition of “real world” data. The pros of registries correspond almost exactly to the drawbacks of RCTs and vice versa. This leads to the attention to registry RCT (rRCTs).

The objective was to analyse methodological features, feasibility challenges and areas of application of rRCTs.

Material/Methods: A systematic literature search was performed (01/2016, MEDLINE). References of discussion papers on rRCTs were cross-checked. We included randomized trials which collected at least one outcome via a registry. Study selection was performed independently by two reviewers.

Information on patients, health technology (HT), outcomes, study design aspects, the registry and country/setting was extracted in standardized tables by one reviewer and 10% were verified by a second.

Results: We included 74 relevant rRCTs. The majority of studies were performed in Scandinavia followed by USA, Canada and UK and evaluated HTs for prevention. Screening and vaccination were evaluated most often, followed by medical devices, surgical procedures, and coordination and organization of care. Sample size of most rRCTs was very large (up to 246.079 patients) and trials had long follow-up periods (up to 27 years). Different types of registries were used to collect data; national patient registries, vaccination registries, death registries and patient registries on chronic diseases. In most of the studies the registry was not the only data source. The outcome that was most often gathered was mortality. Information on data quality (e.g. missing values) was often insufficient. In studies that did not use the registry as the only data source, data were commonly linked via the personal social insurance number. In studies that exclusively used registry data, mostly a randomization indicator was included in the registry.

Conclusion: A considerable amount of rRCTs exists. rRCT seem a valuable tool to gather effectiveness data. Our analyses showed that rRCTs allow an efficient recruitment of large sample sizes and a long-term assessment of patient important outcomes. For the use in systematic reviews the reporting of information on the registry must be improved to enable a sufficient assessment of data validity.