Missing data are ubiquitous in medical research. Although there is increasing guidance on how to handle missing data, practice is changing slowly and misapprehensions abound, particularly in observational research. Importantly, the lack of transparency around methodological decisions is threatening the validity and reproducibility of modern research. We present a practical framework for handling and reporting the analysis of incomplete data in observational studies, which we illustrate using a case study from the Avon Longitudinal Study of Parents and Children. The framework consists of three steps: 1) Develop an analysis plan specifying the analysis model and how missing data are going to be addressed. An important consideration is whether a complete records' analysis is likely to be valid, whether multiple imputation or an alternative approach is likely to offer benefits and whether a sensitivity analysis regarding the missingness mechanism is required; 2) Examine the data, checking the methods outlined in the analysis plan are appropriate, and conduct the preplanned analysis; and 3) Report the results, including a description of the missing data, details on how the missing data were addressed, and the results from all analyses, interpreted in light of the missing data and the clinical relevance. This framework seeks to support researchers in thinking systematically about missing data and transparently reporting the potential effect on the study results, therefore increasing the confidence in and reproducibility of research findings.
Isolated sheets of sheep rumen mucosa were studied in vitro by using the Ussing chamber technique. The pH of the mucosal solution was altered by adding HCl. Using 22Na and 36Cl unidirectional fluxes of sodium and chloride were measured across the short-circuited and voltage-clamped rumen mucosa at mucosal pH 7.4 and 5.5. Lowering mucosal pH to 5.5 caused a rapid decline in the short-circuit current (Isc). The conductance (Gt) increased about 10 min after the drop in Isc. At pH 5.5, mucosal-to-serosal movement of Na+ and Cl- was decreased thus leading to a decreased net transport. These alterations were seen 30 min after mucosal acidification. They were intensified 120 min thereafter. Further studies showed that a clamped transmural potential difference (20 mV) influenced Na+ and Cl- transport only slightly more in acidified epithelia. Light and electron microscopy showed a swelling of the cells and especially of their mitochondria after acid exposure. These data indicate that lowering mucosal pH causes alterations in transepithelial Na+ and Cl- transport. We suggest a predominant effect on cellular transport mechanisms.
On a HC diet, the subjects who had a higher positive CHO balance on day 15 while they were inactive gained less fat mass during 4 y, a predictive effect independent of S(I). As suggested in rodents, the capacity to expand the glycogen pool might reduce energy intake and protect against fat and weight gain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.