Low lactase levels: Evaluation of the radiologic diagnosis

23 patients with low lactase levels and 13 lactase normal subjects (as determined by disaccharidase assay of jejunal biopsy) underwent a regular small bowel series, a small bowel series with 25 g lactose added to barium sulfate, and a lactose tolerance test. The lactose barium small bowel study is a sensitive and specific test for individuals with low lactase levels that compares favorably with the lactose tolerance test. The 1 hr lactose barium study, evaluated as a screening procedure, was 90% accurate in predicting low lactase individuals but had an overall 10% false positive rate in lactase normal subjects.