Reporting of "Theoretical Design" in Explanatory Research: A Critical Appraisal of Research on Early Life Exposure to Antibiotics and the Occurrence of Asthma.

"Theoretical design" comprises the development of an occurrence relation and the specification of the study domain. In explanatory research, the occurrence relation causally relates one determinant to the occurrence (of an event or a state) taking into account other relevant characteristics (confounders and modifiers). Conflicting results in explanatory research might be (partially) explained by differences in the "theoretical design" or by a mismatch between the "theoretical design" and the "design of data collection". In this critical review, the reporting of "theoretical design" is assessed in articles on the association between early life antibiotic use and the occurrence of asthma. Articles investigating a relationship between early life antibiotic use and the occurrence of asthma were searched in PubMed and systematically selected for critical review. The full text was read and important elements of study design were extracted (the research question/hypothesis, seven key elements of "theoretical design" (measure of occurrence, case (event or state) definition, conceptualization (and operationalization) of the exposure, temporal relation between outcome and exposure, confounders and effect modifiers taken into account and the domain of the study), the method of data collection and the method of data processing). A comparison was made between articles published before and after the publication of the "Strengthening the Reporting of Observational Studies in Epidemiology" (STROBE) statement (2007). Sixty-three articles were included for review. Thirteen articles reported the seven key elements of "theoretical design" that were questioned. No marked differences in reporting were observed pre- and post-STROBE. All articles reported some key elements of "theoretical design"; however, the reporting is not structured and not linked to the concept of "theoretical design". Conceptualizing, delineating and explicit reporting of "theoretical design" is quintessential for the quality and transparency of explanatory research.