Evaluation of a new biopsy urease test: Pronto Dry, for the diagnosis of Helicobacter pylori infection

BACKGROUND: The gastric biopsy urease test is the most frequently used test for the diagnosis of Helicobacter pylori infection in routine gastrointestinal endoscopy practice. In Malaysia up to recently, only one commercial biopsy urease test was available: the CLO test (Ballard Medical Products, Draper, Utah, USA). Large endoscopy units use their own 'homemade' unbuffered ultra rapid urease test for diagnosis of H. pylori infection.

OBJECTIVE: To compare the accuracy and reaction time of a new biopsy urease test, Pronto Dry (Medical Instruments Corporation, Solothurn, Switzerland) and the CLO test in the diagnosis of H. pylori infection.

METHODS: Consecutive patients presenting with dyspepsia to the endoscopy unit, University of Malaya Medical Centre were recruited for the study. Patients who were previously treated for H. pylori infection or who had received antibiotics, proton pump inhibitors or bismuth compounds in the preceding 4 weeks were excluded. H. pylori diagnosis was made based on the ultra rapid urease test and histological examination of gastric biopsies. Four antral and four corpus biopsies were taken for this purpose from all patients. A diagnosis of H. pylori infection was made when both the ultra rapid urease test and histology were positive in either the antral or corpus biopsies. A negative diagnosis of H. pylori was made when both tests from antral and corpus biopsies were all negative. Another four antral and four corpus biopsies (two each) were taken for the Pronto Dry and CLO tests. The Pronto Dry and CLO tests were stored and performed according to the manufacturer's instruction.

RESULTS: Two hundred and eight patients were recruited in the study. Eighty-six of the patients were males and 122 were females. The mean age was 46.3 years with a range of 15-82 years. The results for both the Pronto Dry and the CLO tests were completely concordant with sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of 98.1%, 100%, 100%, 98.1% and 99%, respectively. The Pronto Dry test showed a faster reaction time to positive compared with the CLO test, with 96.2% positive reaction by 30 min versus 70.8% and 100% positive reaction time by 55 min versus 83%. The colorimetric change was also more distinct with the Pronto Dry test compared with the CLO test.

CONCLUSIONS: Both the Pronto Dry and the CLO tests were highly accurate for the diagnosis of H. pylori infection. The Pronto Dry test showed a quicker positive reaction time and the positive colour change was more distinct.