Confidence Intervals with Birth Defects SurveillanceData: A Tempest in a Teapot or Honestly Significant

Differences of Opinion?

Pamela Costa1 and Russell S. Kirby2

1National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA 303412University of Alabama-Birmingham, Birmingham, AL 35294-0022

The article which follows can stand on its own merit, butreaders unfamiliar with the history of the National BirthDefects Prevention Network (NBDPN) may benefit fromsome introductory comments. For the past several years,both at National Birth Defects Prevention Network annualmeetings and during task-oriented conference calls, thesubject of the use of confidence intervals in statistical tab-ulations and summaries of surveillance data has generatedpassionate, but friendly, debate. Recognizing that theseextended conversations may otherwise continue ad infini-tum, perhaps deflecting attention from more serious scien-tific and methodological issues, NBDPN in its traditionalstyle organized a subcommittee to offer some solutions.The subcommittee, chaired by Pam Costa, realized that thisis not a subject where people’s opinions were likely to bechanged, nor perhaps, a consensus reached. However, inorder for the work of the NBDPN to go forward, thesub-committee felt that the key issues had to be identifiedand addressed in an objective manner. Subsequently, thesub-committee decided to pursue the development of amanuscript(s) that would incorporate the best statisticalthinking into a balanced presentation of the issues at hand.

The subcommittee sought out and then invited severalmathematical statisticians and birth defects epidemiolo-gists to prepare statements, both ‘pro’ and ‘con’, on thesubject of whether and when it is appropriate to use con-fidence intervals in birth defects surveillance reports. Toensure a balanced approached, representatives of each ofthe two positions were asked to draft their thoughts andshare them with the other side. In this manner, the sub-committee felt that the most comprehensive and thoroughdiscussions would be prepared and presented. As theworking group engaged in its work it became apparent

that it would make more sense to organize the discussioninto a single paper, addressing the issues of random errorin samples and ascertainment bias (especially undercount-ing) in surveillance databases. After numerous conferencecalls and drafts, the paper appearing here took form.

This paper presents the culmination of the dedicatedefforts of the authors. They are to be commended forgenerating such a balanced and objective presentation ofissues that originally came from passionate opinions. Weare not so naı̈ve as to believe that this publication will settlethe question of whether to publish confidence intervals inreports or scientific publications derived from birth defectssurveillance data. We do feel, however, that this paperpresents the primary issues researchers should consider inmaking this decision. As always, the choice ultimatelyremains for the reader to make.

ACKNOWLEDGMENTSThe Confidence Interval Sub-Committee of the NBDPN

Data Committee: Pam Costa (Chair, CDC), Leslie Beres-Sochka (New Jersey Department of Health and Senior Ser-vices), Adolfo Correa (CDC), Charlotte Druschel (NewYork State Department of Health), Jane Fornoff (IllinoisDepartment of Public Health), Tracy Miller Jewell (Ken-tucky Department of Pubic Health), Russel Kriby (Univer-sity of Alabama, Birmingham), and Cara Mai (CDC).

†This article is a US government work and, as such, is in the public domain inthe United States of America.Published online in Wiley InterScience (www.interscience.wiley.com).DOI: 10.1002/bdra.10109

Published 2003 Wiley-Liss, Inc.† Birth Defects Research (Part A) 67:609 (2003)

Birth Defects Research (Part A): Clinical and Molecular Teratology 67:609 (2003)