Starting with 8-h intervals from time-point 1 to 37, we decreased the frequency of image data collection, or "skipped" interim time-points, which diminished the density of the overall dataset.
Setting Five NHS acute hospital and mental health trusts that have been the focus of early implementation efforts and at which interim data collection and analysis are complete.
Therefore, based on current literature, we defined a priori a set of parameters for data collection regarding DMC characteristics, interim analysis and early termination.
The study design also did not allow for interim data collection so non-fatal end points, such as hospitalisation, were not explored.
The survey is an interim data collection of a nationally representative survey conducted every fourth year constituting the Danish contribution to the cross-national Health Behaviour in School-aged Children (HBSC) survey [ 1, 17].
About 40% of the delivery data were missed when using the original data collection method and the interim birth data were available for 1109 (51%) in the Routine iron group and for 1149 (54% of women) in the Selective iron group.
Women who move from their primary residence (their home at the time of recruitment) are not followed up at interim data collection visits, but extensive effort is made to trace and follow all women residing anywhere within Zimbabwe at the 18-month visit to collect trial endpoints for the intent-to-treat analyses.
We developed inter- and intra- reliability modules that allowed for interim feedback during data collection.
The strategy consisted of frequent contact information validity probes, an interim evaluation, and data collection wave, conducting study impact focus groups, maintaining community advisory board contacts, implementing field-based tracking and tracing, developing electronic tracking and tracing protocols, and mail and telephone contact protocols.
We thank the technical experts who provided support to one or more phases of the study and the participants in the project workshop that was held in Geneva to discuss the data-collection process, interim findings, and potential implications for dissemination and next steps.
