Can non-invasive tests substitute for histology in the diagnosis of Helicobacter pylori (Hp infection?

Introduction: Rapid urease tests (RUT, e.g. CLOtest or Pyloritek) are performed during endoscopy to evaluate for Hp. RUT sensitivity varies from 80-90%, there-fore, many recommend histological examination of gastric biopsies to rule out Hp in RUT-negative patients. However, non-invasive tests may provide a more rapid diagnosis and be less expensive. Aim: Determine, if non-invasive tests (Urea Breath Test (UBT), serology, whole blood antibody tests) can substitute for histology in RUT-negative patients. Methods: 57 patients without prior treatment for Hp, not taking proton pump inhibitors, antibiotics, or bismuth within 4 weeks, underwent endoscopy for dyspepsia and tested RUT-negative (CLOtest or Pyloritek) by antral biopsy. All had the following: gastric biopsies (2 antral, 1 fundus; H&E, Alcian Yellow stain) examined for gastritis and Hp bacteria; 13C-UBT (Meretek; specimens mailed to the manufacturer for analysis); capillary blood by finger-prick for 3 commercially available tests: FlexSure HP (FS-WB, SmithKline Diagnostics, Inc. [SKD]), Quickview (QV, Quidel), and Accustat (Acc, Boehringer Mannheim) and one non-commercially available test (SDS, Saliva Diagnostic Systems); fresh serum for FlexSure HP (FS-Ser, SKD), and frozen serum sent to SKD for a commercially available EIA (HM-CAP). Hp was diagnosed if at least two of these three tests were positive: UBT, Hp identified on Histology, HM-CAP. Cost per patient ($US) was calculated using the cost per test plus the price of metronidazole, clarithromycin, and omeprazole treatment b.i.d. for 10 days ($200/patient) for all positive patients (AP) by each test. Results: AP TP AN TN Test Cost ($) Cost/Patient ($) Histology 2 2 55 53 199 206**UBT 10 4 47 47 125 164*HM-CAP 5 4 52 52 81 99*FS-WB 9 4 47 47 10 42 FS-Ser 7 4 48 48 10 35 QV 6 4 51 51 13 34 Acc 5 4 52 52 10 28 SDS 4 4 49 49 12 27 Excluded from analysis due to technical test failure: 1 FS-WB, 2 FS-Ser, 3 SDS. AP = All positive; TP = True positive; AN = All negative; TN = True negative.*p<0.001 vs. rapid antibody tests(t test)**p<0.001 vs. non-invasive tests(t test). Conclusions: Whole blood antibody testing is a rapid, accurate, and cost-effective means for establishing Hp-status in RUT-negative patients. Whole blood testing or serology should substitute for histology for diagnosis of Hp when the patient has not been previously treated for Hp. The UBT seems less specific than expected in RUT-negative patients.