Evaluation of the reported data linkage process and associated quality issues for linked routinely collected healthcare data in Multimorbidity research: a systematic review

Abstract

Background: Datasets from multi-sources that routinely collect healthcare information such as patient medical records, admissions and disease registries are increasingly used for medical research. In some cases, multiple sources are combined using data linkage techniques to create comprehensive datasets. The patient records are linked on an individual level using available person level identifiers. Errors in this process can introduce bias of unknown size and direction. the objective of this systematic review was to examine how the record linkage process was reported and to understand challenges related to accessing, linking, and analysing linked routinely collected data. Methods: A systematic search for relevant studies was conducted in three online databases (Medline, Web of Science and Embase) in May 2021 using predefined search terms, and inclusion and exclusion criteria. All published studies using linked routinely collected data for multimorbidity research were included. Information was extracted on how the linkage process was reported, which conditions were studied together, which data sources were used, as well as challenges encountered during the linkage process or with the linked dataset. Results: Twenty studies were included, of which seventeen investigated at the relationship between two specified long-term conditions. Fourteen studies received the linked dataset from a trusted third party. Hospital Episode Statistics was the most common source of data (n = 5). Eight studies reported variables used for the data linkage, while only two studies reported pre-linkage checks. The quality of the linkage was assessed only by three studies, of which two reported linkage rate and one reported raw linkage figures. Only one study checked for bias by comparing patient characteristics of linked and non-linked records. Conclusions: The linkage process was poorly reported in multimorbidity research, even though this might introduce bias and potentially lead to inaccurate inferences drawn from the results. There is therefore a need for increased awareness of linkage bias and transparency of the linkage processes, which could be achieved through better adherence to reporting guidelines.