Diagnostic criteria for autoimmune hepatitis: What is the gold standard?
Authors: Rajan Kochar, Michael Fallon
Journal: Hepatology (2009)

We read the article by Yeoman et al. with great interest.1 They identified patients with autoimmune hepatitis (AIH) retrospectively from a single tertiary referral center in order to examine the validity and utility of the simplified diagnostic criteria for the diagnosis of AIH proposed by the International Autoimmune Hepatitis Group (IAIHG).2 The authors also assessed the utility of the diagnostic criteria for AIH in the specific patient group presenting with fulminant hepatic failure (FHF). Although they deserve credit for being the first to assess the utility of these criteria, there are several issues that merit discussion. First, the criteria used by the authors to classify study patients as having a diagnosis of AIH are unclear. Because there is no perfect "gold standard" test for the diagnosis of AIH, it is possible that some of the 221 study patients were misdiagnosed as AIH. However, the sensitivity and specificity of both the scores (simplified diagnostic criteria and the original revised 1999 IAIHG criteria) for a probable or definite diagnosis of AIH were calculated assuming 100% accuracy of the study patients' diagnoses of AIH. Therefore, caution must be exercised while interpreting these results. Second, only those patients were included in the study that had all the demographic, clinical, and laboratory information required for calculating scores for both the diagnostic criteria. This may have resulted in the selective inclusion of patients with severe or complicated disease, because these patients are more likely to have extensive testing. This could lead to overestimation of accuracy of the diagnostic criteria because more patients would have autoimmune antibody testing or could lead to underestimation of the accuracy if the majority of these patients were complicated and difficult to diagnose. Third, the authors demonstrate the increased sensitivity of the simplified diagnostic criteria after addition of the "responsiveness to steroids" variable, advocating its inclusion as the fifth criterion. We acknowledge the utility of responsiveness to steroids in aiding the diagnosis of AIH; however, these criteria were formulated to allow "bedside" diagnosis in routine clinical practice and to guide management. Application of the criteria after steroid therapy has been instituted would only be useful in retrospect. In addition, including response to steroid therapy would render the two criteria near identical in their applicability and ease of use. Finally, the authors emphasize the lower sensitivity of the simplified criteria for 'definite' diagnosis of AIH (70%) compared to "overall" diagnosis of AIH (90%) and suggest this as the major limitation. However, since majority of the patients diagnosed as "probable" AIH using the simplified criteria would be treated in a fashion similar to those diagnosed as "definite" AIH, we would argue that the sensitivity for "overall" diagnosis of AIH is more relevant. In summary, the results of this study are difficult to interpret because the accuracy of AIH diagnosis in study patients is unknown. Until a reliable gold standard test for AIH is devised to accurately assess the sensitivity and specificity of these criteria, it would be prudent to limit their use as an adjunct to clinical judgement in guiding diagnosis and management of patients with AIH. Rajan Kochar*, Michael Fallon*, * Division of Gastroenterology & Nutrition Hepatology, The University of Texas Health Science Center at Houston, Houston, TX.