SHELF-LIFE OF UNBUFFERED RAPID UREASE TEST

Background, Unbuffered rapid urease test (RUT) is an accurate and inex pensive method to detect Helicobacter pylori. However, the test is not always readily available because the reagents must be mixed freshly o r stored at -20 degrees C after mixing. From our experience, storage a t 4 degrees C for less than 6 days seemed to have no effect on the tes t's accuracy. This prospective study was undertaken to evaluate the sh elf life of our unbuffered RUT. Material and Methods. Forty-five patie nts were studied. From all patients, two sets of antral biopsy (X2) an d body biopsy (X1) were taken. One set was subjected to histological e xamination; the other set was placed into a single capped Eppendorff t ube for RUT. The tube was examined for any color change at 1 and 5 min utes. Results. Twenty-six patients (58%) were infected as defined by h istological examination. The reagent was classified according to the s torage time (group 1, less than or equal to 5 days; group 2, > 5 days) . The mean storage times of group I (n = 24) and group 2 (n = 21) were 3.1 (1.7 SD) days and 7.7 (1.2 SD) days, respectively. At 1 and 5 min utes, the sensitivity of group 1 was consistently higher than that of group 2 (1 minute, 61% versus 38%; 5 minutes, 92% versus 62%), and no false-positive result was observed in either group. Conclusion, RUT re mains highly sensitive and specific when it was stored at 4 degrees C for up to 5 days but should be discarded after that period.