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.