Comparison of Accuracy Between ¹³C- and ¹⁴C-Urea Breath Testing: Is an Indeterminate-Results Category Still Needed?

Helicobacter pylori infection is the leading cause of peptic ulcer disease. The purpose of this study was, first, to assess the difference in the distribution of negative versus positive results between the older ¹⁴C-urea breath test and the newer ¹³C-urea breath test and, second, to determine whether use of an indeterminate-results category is still meaningful and what type of results should trigger repeated testing. Methods: A retrospective survey was performed of all consecutive patients referred to our service for urea breath testing. We analyzed 562 patients who had undergone testing with ¹⁴C-urea and 454 patients who had undergone testing with ¹³C-urea. Results: In comparison with the wide distribution of negative ¹⁴C results, negative ¹³C results were distributed farther from the cutoff and were grouped more tightly around the mean negative value. Distribution analysis of the negative results for ¹³C testing, compared with those for ¹⁴C testing, revealed a statistically significant difference between the two. Within the ¹³C group, only 1 patient could have been classified as having indeterminate results using the same indeterminate zone as was used for the ¹⁴C group. This is significantly less frequent than what was found for the ¹⁴C group. Discussion: Borderline-negative results do occur with ¹³C-urea breath testing, although less frequently than with ¹⁴C-urea breath testing, and we will be carefully monitoring differences falling between 3.0 and 3.5 %Δ. ¹³C-urea breath testing is safe and simple for the patient and, in most cases, provides clearer positive or negative results for the clinician.