First record: a methodological approach to counter sampling bias

The use of Geographic Information System (GIS) and non-GIS methods to assess the external validity of samples postcollection

External validity is fundamental to veterinary diagnostic investigation, reflecting the accuracy with which sample results can be extrapolated to a broader population of interest. Probability sampling methods are routinely used during the collection of samples from populations, specifically to maximize external validity. Nonprobability sampling (e.g., of blood samples collected as part of routine surveillance programs or laboratory submissions) may provide useful data for further posthoc epidemiological analysis, adding value to the collection and submission of samples. As the sample has already been submitted, the analyst or investigator does not have any control over the sampling methodology, and hence external validity as routine probability sampling methods may not have been employed. The current study describes several Geographic Information System (GIS) and non-GIS methods, applied posthoc, to assess the external validity of samples collected using both probability and nonprobability sampling methods. These methods could equally be employed for inspecting other datasets. Mapping was conducted using ArcView 9.1. Based on this posthoc assessment, results from the random field sample could provide an externally valid, albeit relatively imprecise, estimate of national disease prevalence, of disease prevalence in 3 of the 4 provinces (all but Ulster, in the north and northwest, where sample size was small), and in beef and dairy herds. This study provides practical methods for examining the external validity of samples postcollection.

Are Front Line Health Professionals Responsible for the Organ Crisis?

The process and techniques of organ transplantation have improved significantly; however, there remains a supply-demand mismatch that appears to grow wider as years go by. In this literature review, databases covering published studies from 1990 to 2006 were searched for studies focused on medical doctors' and/or registered nurses' attitudes towards human-to-human organ donation and/or transplantation. The results indicate that healthcare professionals do play a significant part in the procurement of organs for transplantation and may be partly responsible for the lack of transplantable organs available. However, the review further illustrates their complex role within the healthcare system, and suggests that responsibility for organ procurement may be best placed within the domain of specialist personnel.