Computed Tomography and Ultrasonography To Detect Appendicitis
Authors: Toshiya Shiga, Zen'ichiro Wajima, Tetsuo Inoue
Journal: Annals of Internal Medicine (2005)

Letters3 May 2005Computed Tomography and Ultrasonography To Detect AppendicitisToshiya Shiga, MD, PhD, Zen'ichiro Wajima, MD, PhD, and Tetsuo Inoue, MD, PhDToshiya Shiga, MD, PhDFrom Nippon Medical School, Chiba Hokusoh Hospital, Chiba 270-1613, Japan.Search for more papers by this author, Zen'ichiro Wajima, MD, PhDFrom Nippon Medical School, Chiba Hokusoh Hospital, Chiba 270-1613, Japan.Search for more papers by this author, and Tetsuo Inoue, MD, PhDFrom Nippon Medical School, Chiba Hokusoh Hospital, Chiba 270-1613, Japan.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-142-9-200505030-00022 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR:We congratulate Terasawa and colleagues (1) for demonstrating the advantage of CT over ultrasonography in the diagnosis of acute appendicitis in adults and adolescents. We note that although they plotted the false-positive rate against the true-positive rate on their graph, they did not construct a summary receiver-operating characteristic (ROC) curve. The summary ROC curve, as described by Moses and colleagues (2), is a powerful tool for depicting diagnostic performance and showing how it is affected by the test threshold. Briefly, the regression model is expressed as D = a + b × S, where D is the diagnostic log odds ratio and S is the measure of how the test characteristics vary with the test threshold. We could not resist plotting summary ROC curves (figure not shown here) from Terasawa and colleagues' 2 × 2 contingency tables. We found that D = 5.2 − 0.49 × S for CT and D = 3.8 − 0.005 × S for ultrasonography.When we compared Terasawa and colleagues' original figure with ours, it was apparent that the diagnostic performance of CT is superior to that of ultrasonography in cases of appendicitis. Terasawa and colleagues stated that in most of the studies they reviewed, appendiceal diameter greater than 6 mm was used as the positive diagnostic criterion for appendicitis. But, judging from their Appendix Table 2, most of the studies seem to have several criteria. However, both regression coefficients b are between −1.0 and 1.0 (P > 0.05), suggesting no significant variation in diagnostic performance with threshold. The diagnostic log odds ratios (logit transformation of the ratio of positive to negative likelihood obtained by the Mantel–Haenszel method) of CT and ultrasonography are estimated to be 5.0 (95% CI, 1.3 to 8.7) and 3.4 (CI, 0.9 to 5.9), respectively, indicating again that CT is superior to ultrasonography.We also created a funnel plot to explore the publication bias. The funnel plot is asymmetric, indicating that publication bias is likely. It is possible that some studies of small samples that indicated low diagnostic accuracy for these tests were not published.Our additional analysis does not mean that Terasawa and colleagues' conclusion needs alteration; rather, it strengthens their conclusion. They provided an elegant systematic review.Toshiya Shiga, MD, PhDZen'ichiro Wajima, MD, PhDTetsuo Inoue, MD, PhDNippon Medical School, Chiba Hokusoh HospitalChiba 270-1613, JapanReferences1. Terasawa T, Blackmore CC, Bent S, Kohlwes RJ. Systematic review: computed tomography and ultrasonography to detect acute appendicitis in adults and adolescents. Ann Intern Med. 2004;141:537-46. [PMID: 15466771] LinkGoogle Scholar2. Moses LE, Shapiro D, Littenberg B. Combining independent studies of a diagnostic test into a summary ROC curve: data-analytic approaches and some additional considerations. Stat Med. 1993;12:1293-316. [PMID: 8210827] CrossrefMedlineGoogle Scholar Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAffiliations: From Nippon Medical School, Chiba Hokusoh Hospital, Chiba 270-1613, Japan.Disclosures: None disclosed. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoSystematic Review: Computed Tomography and Ultrasonography To Detect Acute Appendicitis in Adults and Adolescents Teruhiko Terasawa , C. Craig Blackmore , Stephen Bent , and R. Jeffrey Kohlwes Computed Tomography and Ultrasonography To Detect Appendicitis Masashi Goto Computed Tomography and Ultrasonography To Detect Appendicitis Teruhiko Terasawa and C. Craig Blackmore Computed Tomography and Ultrasonography To Detect Appendicitis Junaid A. Razzak Metrics 3 May 2005Volume 142, Issue 9Page: 798-799KeywordsAdolescentsAppendicitisComputed axial tomographyConflicts of interestSystematic reviewsUltrasound imaging ePublished: 3 May 2005 Issue Published: 3 May 2005 CopyrightCopyright © 2005 by American College of Physicians. All Rights Reserved.PDF DownloadLoading ...