Allternative Metrics ("Altmetrics") for Assessiing Artricle Impact in Populer General Radiology Journals

Rationale and Objectives: Emerging alternative metrics leverage social media and other online platforms to provide immediate measures of biomedical articles' reach among diverse public audiences. We aimed to compare traditional citation and alternative impact metrics for articles in popular general radiology journals. Materials and Methods: All 892 original investigations published in 2013 issues of Academic Radiology, American Journal of Roentgenology, Journal of the American College of Radiology, and Radiology were included. Each article's content was classified as imaging vs nonimaging. Traditional journal citations to articles were obtained from Web of Science. Each article's Altmetric Attention Score (Altmetric), representing weighted mentions across a variety of online platforms, was obtained from Altmetric.com. Statistical assessment included the McNemar test, the Mann-Whitney test, and the Pearson correlation. Results: Mean and median traditional citation counts were 10.7 +/- 15.4 and 5 vs 3.3 +/- 13.3 and 0 for Altmetric. Among all articles, 96.4% had traditional citation vs 41.8% for Altmetric (P < 0.001). Online platforms for which at least 5% of the articles were represented included Mendeley (42.8%), Twitter (34.2%), Facebook (10.7%), and news outlets (8.4%). Citations and Altmetric were weakly correlated (r = 0.20), with only a 25.0% overlap in terms of articles within their top 10th percentiles. Traditional citations were higher for articles with imaging vs nonimaging content (11.5 +/- 16.2 vs 6.9 +/- 9.8, P < 0.001), but Altmetric scores were higher in articles with nonimaging content (5.1 +/- 11.1 vs 2.8 +/- 13.7, P = 0.006). Conclusions: Although overall online attention to radiology journal content was low, alternative metrics exhibited unique trends, particularly for nonclinical articles, and may provide a complementary measure of radiology research impact compared to traditional citation counts.