Diagnostic accuracy of reused Pronto Dry® test and CLOtest® in the detection of Helicobacter pylori infection

Background: Unchanged substrate in a negative rapid urease test may be reused to detect Helicobacter pylori (H. pylori). This could potentially reduce costs and wastage in low prevalence and resource-poor settings. We thus aimed to investigate the diagnostic accuracy of reused Pronto Dry® and CLOtest® kits, comparing this to the use of new Pronto Dry® test kits and histopathological evaluation of gastric mucosal biopsies. Methods: Using a cross-sectional study design, subjects who presented for upper endoscopy due to various non-emergent causes had gastric biopsies obtained at three adjacent sites. Biopsy samples were tested for H. pylori using a reused Pronto Dry® test, a reused CLOtest®, a new Pronto Dry® test and histopathological examination. Concordance rates, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy were then determined. Results: A total of 410 subjects were recruited. The sensitivity and diagnostic accuracy of reused Pronto Dry® tests were 72.60 % (95 % CI, 61.44 - 81.51) and 94.15 % (95 % CI, 91.44 - 96.04) respectively. For reused CLOtests®, the sensitivity and diagnostic accuracy were 93.15 % (95 % CI 85.95 - 97.04) and 98.29 % (95 % CI 96.52 - 99.17) respectively. There were more true positives for new and reused Pronto Dry® pallets as compared to new and reused CLOtests® when comparing colour change within 30 min vs. 31-60 min (P < 0.001 and P = 0.7 respectively). Conclusion: Negative Pronto Dry® and CLOtest® kits may be reused in a low prevalence setting where cost issues remain paramount. Reused CLOtest® kits have better accuracy than reused Pronto Dry® tests. Reused Pronto Dry® tests however have a more rapid colour change whilst maintaining diagnostic accuracy.