Observational Study Design in Veterinary Pathology, Part 1: Study Design

Abstract

Observational studies are the basis for much of our knowledge of veterinary pathology and are highly relevant to the daily practice of pathology. However, recommendations for conducting pathology-based observational studies are not readily available. In part 1 of this series, we offer advice on planning and conducting an observational study with examples from the veterinary pathology literature. Investigators should recognize the importance of creativity, insight, and innovation in devising studies that solve problems and fill important gaps in knowledge. Studies should focus on specific and testable hypotheses, questions, or objectives. The methodology is developed to support these goals. We consider the merits and limitations of different types of analytic and descriptive studies, as well as of prospective vs retrospective enrollment. Investigators should define clear inclusion and exclusion criteria and select adequate numbers of study subjects, including careful selection of the most appropriate controls. Studies of causality must consider the temporal relationships between variables and the advantages of measuring incident cases rather than prevalent cases. Investigators must consider unique aspects of studies based on archived laboratory case material and take particular care to consider and mitigate the potential for selection bias and information bias. We close by discussing approaches to adding value and impact to observational studies. Part 2 of the series focuses on methodology and validation of methods.

Morphological features of hepatic lipid changes in bearded dragons (Pogona vitticeps), and a proposed grading system

“…5 Finally, due to limited access to case information, it was not possible to determine whether cases were from the same household or pet store, which could have resulted in clustering of data and bias. 5…”

Pathology Principles and Practices for Analysis of Animal Models

“…47,48,50,[64][65][66][67] As clinical trials are increasing and the effectiveness of new chemotherapeutic drugs and other treatment modalities is studied, it has become necessary to devise numeric-based scoring systems that measure treatment efficacy and outcomes for specific diseases (Meyerholz et al 2018 [this issue]). [68][69] Depending on the goals of the study, the pathologist may devise a specific semiquantitative scoring scheme based on recommendations in the literature and on the biology of the specific model. Semiquantitative scoring systems assign numeric grades and yield ordinal data.…”

“…Comparative pathologists may be found in academia, commercial diagnostic laboratories, industry via a contract research organization or biopharmaceutical company, as well as independent consultants, but as of yet, there is no central registry or resource for finding experienced pathologists. 68 Pathologists may be accessed via social media oulets such as LinkedIN. 73 The Comparative Pathologist Consortium on LinkedIN is a social network and resource for comparative pathologists.…”

Observational Study Design in Veterinary Pathology, Part 2: Methodology

“…This is essential for major findings that change routine practice. Cancer grading schemes are an example: a new grading scheme is not rock solid until it has been validated in a second population of study subjects (see Hill’s criterion of consistency 6 ). We have illustrative examples of this in veterinary pathology.…”