Procedures in the ¹³C octanoic acid breath test for measurement of gastric emptying: analysis using Bland–Altman methods

Abstract

Objective. The ¹³C octanoic acid breath test (OBT) was first developed as an alternative method of measuring gastric emptying (GE) to scintigraphy. There has been much debate about the test duration and how often measurements need to be taken. This study aims to address these issues. Material and methods. For 78 GE tests using the ¹³C OBT, GE lag phase (T_lag) was calculated while sampling more frequently than the recommended every 15 min. Comparisons between T_lag were completed using Bland–Altman plots. Similarly, 4 or 6 h test durations were assessed to establish if they yield the same GE half time (T_half). From one volunteer, samples were taken every 1 min for the first 30 min and then every 15 min until 6 h. GE times were then calculated using different combinations of sampling times. Evidence of a visible T_lag was also explored from this data. Results. Findings indicated that taking samples every 5 min for the first 30 min instead of every 15 min did not change the GE T_lag based on Bland–Altman plots. The correlation between these two methods was also high (r² = 0.9957). The findings showed that the difference between the two sampling durations 4 and 6 h was large and the correlation between the methods was low (r² = 0.8335). Samples taken at a rate of one breath per min indicated lack of a visible T_lag. Conclusions. Sampling for the ¹³C OBT should be completed every 15 min for 6 h.

Key Words::

• ¹³C octanoic acid breath test
• gastric emptying
• half time
• lag phase

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.