Correction: Ultrasonography Screening for Abdominal Aortic Aneurysms
Authors: Janelle M. Guirguis-Blake, Tracy L. Beil, Evelyn P. Whitlock
Journal: Annals of Internal Medicine (2016)

Corrections5 January 2016Correction: Ultrasonography Screening for Abdominal Aortic AneurysmsFREEJanelle M. Guirguis-Blake, MD, Tracy L. Beil, MS, and Evelyn P. Whitlock, MD, MPHJanelle M. Guirguis-Blake, MDFrom University of Washington, Tacoma, Washington, and Kaiser Permanente Center for Health Research, Portland, Oregon., Tracy L. Beil, MSFrom University of Washington, Tacoma, Washington, and Kaiser Permanente Center for Health Research, Portland, Oregon., and Evelyn P. Whitlock, MD, MPHFrom University of Washington, Tacoma, Washington, and Kaiser Permanente Center for Health Research, Portland, Oregon.Author, Article, and Disclosure Informationhttps://doi.org/10.7326/L160010 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR:In our article, "Ultrasound Screening for Abdominal Aortic Aneurysms: A Systematic Evidence Review for the U.S. Preventive Services Task Force" (1), we state that neither the individual population-based abdominal aortic aneurysm (AAA) screening trials, nor our pooled analysis of these trials, showed a statistically significant reduction in all-cause mortality. However, a careful reader, Frank Lederle, pointed out that the authors of MASS (Multicentre Aneurysm Screening Study), a large, good-quality trial, reported their hazard ratio (HR) for all-cause mortality to be statistically significant at 13-year follow-up (HR, 0.97 [95% CI, 0.95 to 0.99]) (2); these data are shown in Table 2 of the manuscript and seem to contradict our statement. Dr. Lederle also questioned whether pooled results for all-cause mortality with upper CIs of 1.00 may in some cases be statistically significant if carried to 3 decimal places. We would like to walk Annals readers through these issues and our series of analyses to clarify what may appear to be discrepancies in our results and conclusions.The overarching issues involved with seemingly contradictory interpretations of the evidence reflect the complexity of analysis for all-cause mortality, whereby the overall effect on this outcome is very small, and statistical significance of pooled results is highly dependent on analytic approaches and decisions. Further, readers should be aware that different risk measures (i.e., HR vs. relative risk [RR]) may affect results. Primarily due to study-level reporting, we focused our synthesis on RR measures to maximize data availability across trials.To harmonize reported outcome measures across trials, we recalculated study-level data to produce an RR for the 13 year timepoint in MASS (RR, 0.985 [CI 0.949 to 0.998]). We rounded this RR point estimate and 95% CI to 2 digits beyond the decimal, as is our convention. As a result, the 95% CI included 1.00 and was not considered statistically significant, in contrast to the study-reported HR. Our use of no more than 2 significant digits is long-standing and we believe appropriate, given that few studies report effect size measures beyond 2 digits, and study-level data are our primary data source. Although we stand by our rounding approach, we acknowledge that different approaches could lead people to somewhat different conclusions, particularly if one adheres to conventional indicators of statistical significance as their primary focus.In summarizing data across trials, we focused on 2 different time points commonly reported by trials to indicate short- and longer-term clinical impact: the initial 3- to 5-year end point available from all 4 trials (3–6), and the 13- to 15-year time frame available from only 3 of the 4 trials (2, 7, 8). Like others in the field, we pooled the longest available follow-up for all 4 included trials; this included the 3.6-year West Australian trial (6). In our original analysis for the U.S. Preventive Services Task Force, we presented pooled results using a random-effects model with the DerSimonian—Laird estimation method, with a sensitivity analysis examining a fixed-effects model, to provide comparisons to the work of previous reviewers in this area. Due to emerging consensus that this model can underestimate the 95% CI when a small number of trials are combined (9), we expanded our meta-analytic approach when developing our Annals manuscript. We also shifted our primary interpretation to emphasize the qualitative synthesis of the data, and to emphasize the more conservative profile likelihood estimation method for any pooled results.As shown in the Table below, the choice of statistical model as well as rounding approach makes subtle differences in the final interpretation of long-term mortality results as "statistically significant" or not. The DerSimonian—Laird random-effects models for all-cause mortality at either 13 to 15 years or longest follow-up do not cross 1.00 at the upper 95% CI bound (RR, 0.986 [CI, 0.972 to 0.999]); however, after rounding to 2 significant digits we concluded a lack of statistical significance at this longest time point. When the profile likelihood random effects model is used, point estimates are quite similar, but the upper bound of the 95% CI crosses 1.00, regardless of rounding. Since we agreed that this approach was most appropriate, we emphasized it as our "bottom line," best estimate of a pooled result for this outcome.Table. Relative Risk, All-Cause Mortality Effect of Abdominal Aortic Aneurysm Screening, Using 2 Random-Effects Models Although details of the analytic approaches can be important to appreciate, we believe that there are other, perhaps more important, considerations when interpreting whether AAA screening is associated with an effect on all-cause mortality. These include the consistency of findings (across analytic approaches), as well as the size and clinical significance of any effect. We believe that these 2 perspectives suggest that any effect of AAA screening on all-cause mortality is slight, if present, and depends on the analytic approach taken and the time point considered. Any uncertainty is offset by a clearly beneficial effect on AAA-related mortality, which has been sufficient for evidencebased policy makers to recommend this screening service (10).To avoid any confusion, we appreciate the opportunity to issue an erratum for Table 2, in order to clarify the source of the data in that table as representing those reported by the trials' authors. The title of Table 2 has been changed to the following: "All-Cause and AAA-Related Mortality Data for 1-Time Screening Trials at the Initial and Longest Follow-up as Reported in the Trials."We have also amended our text reflecting the summary findings to clarify our results. On page 324, the word "consistent" has been added to the first sentence of the first full paragraph. The sentence now reads as follows: "An invitation to AAA screening was not associated with a consistent statistically significant all-cause mortality benefit in any of the individual trials or in the pooled random-effects analysis at any time point up to 15 years…"These corrections have been made in the online version.References1. Guirguis-Blake JM, Beil TL, Senger CA, Whitlock EP. Ultrasonography screening for abdominal aortic aneurysms: a systematic evidence review for the U.S. Preventive Services Task Force. Ann Intern Med. 2014;160:321-9. [PMID: 24473919]. doi:10.7326/M13-1844 LinkGoogle Scholar2. Thompson SG, Ashton HA, Gao L, Buxton MJ, Scott RA; Multicentre Aneurysm Screening Study (MASS) Group.. Final follow-up of theMulticentre Aneurysm Screening Study (MASS) randomized trial of abdominal aortic aneurysm screening. Br J Surg. 2012;99:1649-56. [PMID: 23034729] doi:10.1002/bjs.8897] CrossrefMedlineGoogle Scholar3. Ashton HA, Buxton MJ, Day NE, Kim LG, Marteau TM, Scott RA, et al; Multicentre Aneurysm Screening Study Group.. The Multicentre Aneurysm Screening Study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial. Lancet. 2002;360:1531-9. [PMID: 12443589] CrossrefMedlineGoogle Scholar4. Scott RA, Wilson NM, Ashton HA, Kay DN. Influence of screening on the incidence of ruptured abdominal aortic aneurysm: 5-year results of a randomized controlled study. Br J Surg. 1995;82:1066-70. [PMID: 7648155] CrossrefMedlineGoogle Scholar5. Lindholt JS, Juul S, Fasting H, Henneberg EW. Screening for abdominal aortic aneurysms: single centre randomised controlled trial. BMJ. 2005;330:750. [PMID: 15757960] CrossrefMedlineGoogle Scholar6. Norman PE, Jamrozik K, Lawrence-Brown MM, Le MT, Spencer CA, Tuohy RJ, et al. Population based randomised controlled trial on impact of screening on mortality from abdominal aortic aneurysm. BMJ. 2004;329:1259. [PMID: 15545293] CrossrefMedlineGoogle Scholar7. Ashton HA, Gao L, Kim LG, Druce PS, Thompson SG, Scott RA. Fifteen-year follow-up of a randomized clinical trial of ultrasonographic screening for abdominal aortic aneurysms. Br J Surg. 2007;94:696-701. [PMID: 17514666] CrossrefMedlineGoogle Scholar8. Lindholt JS, Sørenson J, Søgaard R, Henneberg EW. Long-term benefit and cost-effectiveness analysis of screening for abdominal aortic aneurysms from a randomized controlled trial. Br J Surg. 2010;97:826-34. [PMID: 20473995] doi:10.1002/bjs.7001 CrossrefMedlineGoogle Scholar9. Cornell JE, Mulrow CD, Localio R, Stack CB, Meibohm AR, Guallar E, et al. Random-effects meta-analysis of inconsistent effects: a time for change. Ann Intern Med. 2014;160:267-70. [PMID: 24727843] LinkGoogle Scholar10. LeFevre ML; U.S. Preventive Services Task Force.. Screening for abdominal aortic aneurysm: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2014;161:281-90. [PMID: 24957320]. doi:10.7326/M14-1204 LinkGoogle Scholar Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAffiliations: From University of Washington, Tacoma, Washington, and Kaiser Permanente Center for Health Research, Portland, Oregon. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoUltrasonography Screening for Abdominal Aortic Aneurysms: A Systematic Evidence Review for the U.S. Preventive Services Task Force Janelle M. Guirguis-Blake , Tracy L. Beil , Caitlyn A. Senger , and Evelyn P. Whitlock Metrics Cited byRetrospective review of abdominal aortic aneurysm deaths in New Zealand: what proportion of deaths is potentially preventable by a screening programme in the contemporary setting?The U.S. Preventive Services Task Force 5 January 2016Volume 164, Issue 1Page: 70-72KeywordsAbdominal aortic aneurysmClinical trial reportingHazard ratioInformation storage and retrievalMortalityRelative riskStatistical dataStatistical modelsSystematic reviewsUltrasound imaging ePublished: 5 January 2016 Issue Published: 5 January 2016 Copyright & PermissionsCopyright © 2016 by American College of Physicians. All Rights Reserved.PDF downloadLoading ...