The CLO test in the UK: inappropriate reading and missed results

Background In endoscopy units, the CLO test is frequently used to detect Helicobacter pylori (H. pylori). informal survey suggested that practice deviated from that recommended, with little account taken of possible confounders such as acid-suppressing medication. Objectives To determine the influence of reading time and acid suppression on CLO tests and to estimate impact on test results in UK endoscopy units. Design Survey of use of CLO tests. Prospective study of time to positivity and concurrent medication in CLO tests from 782 patients. Setting Forty-eight endoscopy units throughout the UK, and a district hospital endoscopy unit. Participants Eighteen endoscopy units in the old Northern Region, and a random sample of 30 other UK units. Main outcome measures Time of reading of CLO tests in UK units, and time to positivity of CLO tests in one hospital. Results Endoscopy units most frequently used CLO tests to assess H. pylori colonization, with marked differences in the times when tests were read. Nineteen out of 37 units discarded tests considerably earlier than the recommended 24 h. Over 20% of CLO tests became positive more than 2 h after collection, with 11% taking 24 h to change colour. Acid-suppressing medication prolonged time to positivity. Conclusions The majority of endoscopy units read tests earlier than recommended. Acid-suppressing medication delays the development of CLO tests and may increase numbers of false-negative tests. Endoscopy units should read tests at 24 h and preferably test patients off ulcer healing medication. (C) 1999 Lippincott Williams & Wilkins.