Negative CLOtest pellet can be reused

Background: The CLOtest is based on the production of ammonia from urea in the presence of urease. In theory, substrate that has not been consumed in a negative test can be reused. Methods: We collected negative CLOtest pellets after their first use and st ored them at room temperature. Whenever a CLOtest was needed during endosco py, two biopsy specimens were taken from the antrum. One specimen was teste d with a new CLOtest and the other with one that had been used previously. Time to color change was observed in paired tests. Results: We used 216 previously used CLOtest pellets with biopsy specimens obtained from 317 patients. Of the paired tests, 204 matched positive and 1 08 tested negative. Only 5 paired tests had discrepant results. Three had p ositive results only with a new CLOtest, and 2 were positive only with the reused test. In positive paired tests, there was significant linear correla tion in log-transformed color change time between reused and new tests (p < 0.001). Ninety-two percent of previously used pellets were reused fewer th an three times before they yielded a positive color change; the interval to this occurrence ranged from 2 to 15 days. Compared with the new CLOtest, t he sensitivity of the reused CLOtest was 98.6% and the specificity was 98.2 %. Conclusions: A negative CLOtest kept at room temperature can be reused with in a short period of time, in circumstances in which there are environmenta l and economic considerations to be taken into account.