Since measurement properties differ between study populations and settings, the PA questionnaire should be proven valid and reliable in the population of interest [ 12].
Despite technological advances in C. difficile microbiology and epidemiology (e.g. genotyping), asymptomatic C. difficile colonization remains as a complex and challenging health problem as its epidemiological features vary considerably between study groups and settings.
In order to enable comparison between different studies and different settings, MRSA rates should be assessed in a standardized way, e.g. the anterior nares should always be included and sampling should be performed by a trained person.
Use of the InterVA method ensured that causes of death were standardized between study settings and over time (a significant advantage in the current study) and classification of asphyxia cases based on probabilistic reasoning relating to multiple causes may overcome misclassification bias associated with lay-reports and alternative methods of verbal autopsy interpretation.
First, known, unknown and/or unrecognized differences between study settings may obstruct generalizability of results.
There were significant differences in the targeted risk factors between study settings: North American studies were more likely to evaluate the economics of interventions addressing smoking, dietary intake and dyslipidemia, while studies assessing interventions within a European context more often addressed high blood pressure and glucose levels.
Studies testing the same hypothesis will tend to find results that match the underlying true effect, but there will be some variation in their results due to differences between studies (different participants, researchers, settings, and so on).
Differences between studies in study designs, settings, data-collection methods, ages and numbers of included children, and types of included MUPS may partly explain the lack of association found in two studies.
