THE DIAGNOSIS OF HELICOBACTER-PYLORI INFECTION IN UREMIC PATIENTS

Two urease-based tests-the urease slide test and the radiolabeled urea breath test, are commonly used for the diagnosis of Helicobacter pylori infection of the stomach. The reliability of these tests in chronic uremia was compared with serological tests for H pylori antibodies, and with direct detection of the organism by microscopy or culture of gastric antral biopsies. Twenty-seven patients with chronic renal failure and dyspepsia underwent upper gastrointestinal endoscopy. Twelve of these patients (46%) were judged to be infected with H pylori on the basis of identification of the organism on microscopy or culture of antral biopsy. Both urease-based tests were able to determine H pylori status, despite the markedly increased concentrations of urea in the gastric juice found in chronic renal failure. The urease slide test performed on antral biopsies obtained at endoscopy proved reliable in determining H pylori status with no false-positive nor false-negative results after 20 minutes and 24 hours of incubation. The 14C-urea breath test also differentiated the infected from the uninfected patients. The 20-minute 14CO2 excretion (kg %dose/mmol CO2 × 100) ranged from 50 to 834 in the H pylori-infected patients, compared with 0.3 to 27 in the H pylori-noninfected patients (P < 0.0001); the 90-minute values ranged from 88 to 398 in the former, compared with 1 to 79 in the latter (P < 0.0001). The excretion of 14CO2 (derived from bacterial hydrolysis of ingested 14C-urea) was higher in all the uremic patients compared with nonuremic controls, and in half of the H pylori-noninfected uremic patients there was a late increase in 14CO2 excretion. On serological testing, nine of 11 patients in the H pylori-infected group were found to have an antibody titer of 20 U/mL or greater, but none of the H pylori-non infected group, giving a sensitivity of 82% and a specificity of 100%. Tests based on detection of the urease activity of H pylori remain a reliable means of determining H pylori status in chronic renal failure, although a higher cutoff value to indicate infection in the 14C-urea breath test is needed. We recommend a value of 50 kg %dose/mmol CO2 × 100 at 20 minutes as the upper limit of normal, rather than the value of 20 kg %dose/mmol CO2 × 100 that is normally used in subjects with normal renal function. © 1992, National Kidney Foundation, Inc.. All rights reserved.