title: Shelf life of unbuffered rapid urease test.
abstract: BACKGROUND
  Unbuffered rapid urease test (RUT) is an accurate and inexpensive method to detect Helicobacter pylori. However, the test is not always readily available because the reagents must be mixed freshly or stored at -20 degrees C after mixing. From our experience, storage at 4 degrees C for less than 6 days seemed to have no effect on the test's accuracy. This prospective study was undertaken to evaluate the shelf life of our unbuffered RUT.
  
  
  METHODS
  Forty-five patients were studied. From all patients, two sets of antral biopsy (X2) and body biopsy (X1) were taken. One set was subjected to histological examination; the other set was placed into a single capped Eppendorff tube for RUT. The tube was examined for any color change at 1 and 5 minutes.
  
  
  RESULTS
  Twenty-six patients (58%) were infected as defined by histological examination. The reagent was classified according to the storage time (group 1, < or = 5 days; group 2, > 5 days). The mean storage times of group 1 (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 minutes, 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.
  
  
  CONCLUSIONS
  RUT remains highly sensitive and specific when it was stored at 4 degrees C for up to 5 days but should be discarded after that period.
authors.affiliation: Department of Medicine, Ruttonjee Hospital, Hong Kong.
authors.forename: F H
authors.initials: FH
authors.lastname: Ng
authors.forename: S Y
authors.initials: SY
authors.lastname: Wong
authors.forename: C M
authors.initials: CM
authors.lastname: Chang
mesh_terms: D001431:Bacteriological Techniques / Q000592:standards*; D005189:False Positive Reactions; D016481:Helicobacter Infections / Q000175:diagnosis* / Q000382:microbiology; D016480:Helicobacter pylori / Q000302:isolation & purification*; D006801:Humans; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014510:Urease
chemical_list: D014510:Urease