Second, the study excluded 158 potential records from the analysis due to missing patient data required to calculate REMS.
Additionally, because of concerns that missing patient obstetrical charts might lead to selection bias [ 21], we systematically recorded the numbers of missing records and patient characteristics (patient age; vaginal birth versus caesarean section) based on data collected from the delivery register.
While it may be possible that women did not experience any complications, given that many other variables were also missing from patient records, it is possible that this information was not recorded.
Moreover, health care providers may not be aware that relevant information is missing in patient records, because of inadequate interoperability between information systems or patients' desire not to disclose certain information.
Within our own study, unquantifiable errors or omissions, that are also likely to be small, will have included missing any non-fatal accidents or DSH that do not present to hospital, and similarly missing patients who leave the area of record, in this case Scotland, before experiencing harm-related events.
The main limitations of our study are related to the single-centre design and the need to retrospectively extract missing data from patient records.
Missing data in patient records makes the calculation of performance measures based on dental records difficult [ 79].
*Sample size may vary due to missing values in the patient records.
The SCORE risk chart was not applicable in 563 patients (51.1%) due to missing data in the patient records, mostly on smoking habits.
We reviewed the registry data for missing or incorrect data items, and sought missing data elements from available patient records.
