Potential waste in evidence synthesis for health screening: a scoping review and call for action

To estimate the extent of potential research waste in the production of evidence-synthesis products for health screening, providing an initial assessment of its magnitude.

Evidence-synthesis products supporting screening recommendations for adult populations, published by the UK National Screening Committee (UK NSC) and the US Preventive Services Task Force (USPSTF) between 2014 and 2024, were identified as anchor reviews. For each anchor review, Embase, Medline, and national and international organization websites were searched for overlapping evidence reviews on the same topic, defined as addressing the same research questions with at least partial overlap in the population, interventions, comparisons, and outcomes.

A total of 48 anchor reviews (covering 33 conditions) were identified from the UK NSC and USPSTF. Overlapping evidence reviews were identified for 92% (44/48) of these, with a median of 4 additional reviews per anchor review (range: 0-60; interquartile range [IQR]: 2-15). Of the overlapping reviews, 11% showed overlap with partial use of prior work, explicitly updating or building upon prior external work, but with new elements and scope differences that maintained their classification as overlapping. Focusing on a core subset of conditions of shared interest to both organizations, the median overlap increased to 13 (range: 2-47; IQR: 4-17), indicating substantial duplication in priority areas. Seventy percent of all reviews in the evidence base were conducted in North America (28%) and Western Europe (42%), with limited representation from low- and middle-income countries.

The results of this review highlight potential research waste due to duplication in evidence synthesis efforts. Coordinated action among organizations advising policymakers, such as NSCs, public health agencies, and evidence review bodies may help establish more efficient, collaborative approaches that enable reuse and adaptation across contexts. Such action could include real-time sharing of ongoing reviews, multiregion comprehensive reviews, and the use of stratified analyses to tailor findings to country-specific needs. These strategies should be explored to determine whether organizations can reduce unnecessary duplication, enhance equity, improve the timeliness and relevance of guidance, and redirect resources toward unmet research priorities and other pressing public health challenges.