Evidence-Based Medicine and Shaken Baby Syndrome: Part I: Literature Review, 1966–1998

In recent years, there has been a clear move toward basing medical practice and opinions on the best available medical and scientific evidence. This process has been termed evidence-based medicine (EBM) and involves a review of the quality of evidence that is available in various diseases and fields of inquiry within medicine. This is the first of 2 articles that attempts to formally rank the available medical scientific evidence by internationally accepted methods, to determine the degree of confidence that can be held on various claims about the condition termed shaken baby syndrome (SBS). Areas with good scientific evidence are identified, and shortcomings in the research and publications on the subject are addressed. Approximately half of all indexed medical publications on the subjects of SBS and shaken-impact syndrome were published before 1999 and half since that time. Given that 1998/1999 is regarded as the turning point in acceptance of the tenets and practice of EBM, it seemed reasonable to assess the quality of evidence before 1999 and compare it with the quality of evidence on the same subject matter since that time. At the conclusion of Part II, the 2 periods are compared to determine the extent to which EBM has affected the field of SBS in terms of quality of available evidence. The aim of this review is to be neutral on the subject of SBS. Neutrality is difficult to define in this field, in part because of the polarization of opinions on the highly emotional subject of infant injury and death and in part because of clear data deficiencies arising from difficulties in performing experiments. It is clearly unethical to intentionally shake infants to induce trauma, and there is an obvious problem with studies and reports that rely on either indirect or disputed evidence of the occurrence, severity, or type of trauma. Many studies lacking these critical data make the obvious logical error of selecting cases by the presence of the very clinical findings and test results they seek to validate as diagnostic. Not surprisingly, such studies tend to find their own case selection criteria pathognomonic of SBS. Neutrality in this review simply means that there is no selective quotation of the available literature, and literature is not chosen to support any particular view. The assessment is of the methods and quality of the actual research, and until this assessment is complete, the content, findings, and recommendations are irrelevant. At the end of the ranking, those studies that achieve the highest QER scores are reviewed for their content, findings, and recommendations. Their outcomes are collated, and the entire published data set is then reviewed as a whole to determine the summarized recommendations, noting areas of agreement, conflict, or controversy. From this, the problems with the published evidence are noted, and data gaps are identified. Recommendations can then be made according to the summarized data. In assessment of the quality of the available scientific evidence, the author has taken an approach recently defined worldwide as an appropriate scale for review of quality of evidence. This approach has been described recently in context of setting Australian clinical guidelines. Genuine hypothesis testing requires use of appropriate research methodologies, including collection of relevant control data, and suitable statistical analysis. The interpretation of individual study findings may be constrained by factors such as whether the cohort examined was adequately representative of the patient population in general. Replication across studies and in independent research centers is a key factor in the reliability of evidence. Compelling evidence comes from consistent findings in 2 or more well-constructed, controlled trials or populationbased epidemiologic studies (i.e., level I or level II evidence). By contrast, clinical practice guidelines with level IV evidence represent consensus statements of the expert panel according to clinical experience and limited scientific data. Although these statements may influence current practice, Manuscript received December 2, 2002; accepted May 29, 2003. From Mosman, New South Wales, Australia. Address correspondence and reprint requests to Mark Donahoe, PO Box 328, Mosman, New South Wales, Australia. E-mail: drmark@bigpond.net. au Copyright © 2003 by Lippincott Williams & Wilkins 0195-7910/03/2403-0239 DOI: 10.1097/01.paf. 0000083635.85457. 97