The importance of disease prevalence in assessing the diagnostic value of a test: Endoscopic markers in celiac disease

Background/Aims: We evaluated the diagnostic variability and reproducibility of endoscopic signs in two populations with a different pretest likelihood of celiac disease (CD). Methods: We recruited 289 CD patients (both adults and children) in a multicenter prospective study. Group 1 (high risk) included 111 patients referred for positive serology. Group 2 (low risk) included 178 unselected patients. Mosaic pattern, reduction/loss of Kerckring's folds, scalloping of the valvulae conniventes and a nodular pattern were the endoscopic findings looked for in the duodenum. Results: In group 1, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of endoscopic findings were 100, 84.6, 94.2 and 100% in adults, and 86.8, 9.1, 82.1 and 12.5% in children. In group 2, the sensitivity, specificity, PPV and NPV of endoscopic findings were 33.3, 91.4, 7.7 and 98.5% in adults, and noncalculable, 78.3, 0.0 and 100% in children. Comparing group 1 and group 2, there was a statistically significant difference in sensitivity and PPV in adults, and in specificity, PPV and NPV in children. Concerning the reproducibility of endoscopic findings, a wide variability of K values was found. Conclusion: Endoscopic signs have low reproducibility for CD, and their diagnostic value in selecting patients for multiple intestinal biopsies is unacceptable, especially in populations with low disease prevalence. Copyright (C) 2013 S. Karger AG, Basel