Schatzki ring, statistically reexamined

In the article by Schatzki published in 1963, data about the lower esophageal ring relate ring diameter to presence of dysphagia. Statistical analysis of these measurements was performed to quantify conclusions of Schatzki and to extract additional information from the data. Ring diameters in 332 patients with and without dysphagia are described in a histogram in the original article of Schatzki. Data were evaluated with analysis of variance, logistic regression, and receiver operating characteristic (ROC) analysis to quantify the relationship between ring diameter and dysphagia. Follow-up information was available in 36 symptomatic and 30 asymptomatic patients of Schatzki. Logistic regression indicated that there was a highly significant difference in ring diameter between the asymptomatic group and patients with recurrent dysphagia (P <.001) but not in patients who had a single episode of dysphagia at presentation (P =.229). Odds ratio of 0.686 indicated that a 1-mm increase in ring diameter decreased the likelihood of dysphagia by 31%; conversely, a 1-mm decrease in ring diameter increased the likelihood of dysphagia by 46%. ROC curve of sensitivity and specificity of ring diameter and symptoms showed that the 20-mm cutoff of Schatzki had a 96% (104 of 108) sensitivity and a 58% (130 of 224) specificity, with area under the ROC curve of 0.888. Retrospective statistical analysis of original data of Schatzki validated his major conclusions about the data. Some important questions remain unanswered because of missing data in the study of Schatzki.