Explaining variations in test ordering in primary care: protocol for a realist review

Variation in diagnostic test ordering is well-documented in primary care settings. While some variation may reflect appropriate clinical judgment, other cases suggest underuse or overuse of tests. Underuse risks diagnostic delays, while overuse can lead to unnecessary interventions and patient harm. Prior research has shown that these patterns are observed across multiple health systems and test types. However, the underlying mechanisms driving these variations remain unclear. Existing studies have not fully explained the contexts and decision-making processes that lead to inconsistent test ordering. This gap motivates the need for a deeper exploration of the factors influencing diagnostic test use. A better understanding is essential to guide interventions that could improve diagnostic accuracy and patient safety. This paper addresses that need through a novel theoretical approach.

This realist review aims to clarify the contexts and mechanisms that influence diagnostic test ordering in primary care. The study seeks to move beyond descriptive accounts of variation by identifying the conditions under which certain tests are ordered or not ordered. The goal is to develop a program theory that explains how and why test ordering decisions are made. This approach will help identify patterns in decision-making that are not apparent through traditional methods. The study will focus on the interplay between clinical settings and practitioner behavior. It will also examine how contextual factors shape test use. By doing so, the review will provide a framework for understanding variability in diagnostic testing. The findings will support the development of targeted interventions to reduce inappropriate test use.

The realist review will follow a theory-driven approach, guided by realist philosophy of science. An initial program theory will be developed in collaboration with stakeholders to frame the review. This theory will be refined through an iterative and purposive search of secondary evidence. The evidence will be gathered from diverse sources to ensure a comprehensive analysis. The data will be analyzed using realist principles to identify patterns in test ordering decisions. The review will focus on the relationships between contexts and generative mechanisms. The findings will be synthesized to produce a refined program theory. The review will be conducted in line with RAMESES standards to ensure transparency and rigor.

The review will produce a refined program theory that explains the contexts and mechanisms behind test ordering decisions in primary care. The analysis will identify the conditions under which tests are considered necessary or unnecessary by clinicians. It will also explore how these decisions are influenced by factors such as patient characteristics, clinical guidelines, and resource availability. The findings will highlight the interplay between clinical judgment and external pressures. The program theory will be tested and refined using available secondary evidence. The results will be structured to show how different contexts lead to different decision-making patterns. The review will also identify gaps in the current evidence base. These findings will inform recommendations for reducing inappropriate test use.

The realist review will provide a detailed explanation of the factors influencing test ordering in primary care. The refined program theory will clarify the contexts and mechanisms that lead to underuse or overuse of diagnostic tests. The findings will support the development of targeted interventions to improve diagnostic accuracy and patient safety. The review will also highlight areas where further research is needed. The program theory will be informed by stakeholder input and secondary evidence. The results will be structured to guide policy and practice improvements. The review will be disseminated to relevant stakeholders to maximize its impact. The approach will serve as a model for future studies on diagnostic test use.