THE ¹³C UREA BREATH TEST (¹³CUBT) - IS A 30-MINUTE SAMPLING INTERVAL NECESSARY?

D Armstrong, V Radovic, M Wolfe, P Bercik, K Croitoru

Division of Gastroenterology, McMaster University, Hamilton, Ontario

BACKGROUND: The ¹³C UBT is widely accepted as a highly accurate, non-invasive test for the diagnosis of active H. pylori infection; extensive validation studies indicate that it has a sensitivity and specificity of ~95-99% using a threshold of d¹³CO₂ of 3.5% when comparing breath samples obtained at baseline and 30-min post ingestion of ¹³C urea.
AIM: To determine whether ¹³C UBT accuracy is reduced if the sampling interval is shortened.
METHODS: Patients undergoing endoscopy and biopsy for histology and culture also completed a ¹³C UBT (Helikit^®, Isodiagnostika, Edmonton, AB) with breath samples obtained at baseline and at 5-minute intervals up to 30 minutes. All breath samples were analysed using an isotope ratio mass spectrometer (BreathMat^TM, Isomass, Calgary, AB); the UBT was considered positive if d¹³CO2 was ³3.5% at 30 minutes.
RESULTS: A total of 65 patients completed the endoscopy and the ¹³C UBT; 15 (23.1%) were H. pylori positive by ¹³C UBT at 30 minutes and, of these, 13 (86.7%) were positive by histology and culture. The remaining 50 (66.9%) were negative by 13C UBT, histology and culture.
At all time points from 10 to 25 minutes post-test dose, the 13C UBT results were the same as those from samples obtained at 30 minutes, using a d13CO2 of 3.5%.
SUMMARY: ¹³C UBT samples obtained 10 minutes post-test dose produced results that were identical to those from a standard, 30-minute test protocol (intraclass correlation coefficient: 0.9373 [95%CI 0.9002-0.9615]).
CONCLUSIONS: The ¹³C UBT is an accurate, non-invasive test even when the sample interval is reduced to 10 minutes; the use of a shorter test protocol should facilitate routine clinical practice and increase patient acceptance with no loss of test performance for the management of H. pylori.

Support: Hamilton Health Sciences Foundation.