title: Procedures in the 13C octanoic acid breath test for measurement of gastric emptying: analysis using Bland-Altman methods.
abstract: OBJECTIVE
  The (13)C 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.
  
  
  METHODS
  For 78 GE tests using the (13)C 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 (r(2) = 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 (r(2) = 0.8335). Samples taken at a rate of one breath per min indicated lack of a visible T(lag).
  
  
  CONCLUSIONS
  Sampling for the (13)C OBT should be completed every 15 min for 6 h.
authors.affiliation: Functional Food Centre, School of Life Sciences, Oxford Brookes University, Oxford, UK. mclegg@brookes.ac.uk
authors.forename: Miriam E
authors.initials: ME
authors.lastname: Clegg
authors.forename: Amir
authors.initials: A
authors.lastname: Shafat
mesh_terms: D000328:Adult; D001944:Breath Tests / Q000379:methods*; D002210:Caprylates; D005260:Female; D005746:Gastric Emptying / Q000502:physiology*; D006801:Humans; D008297:Male; D013997:Time Factors
chemical_list: D002210:Caprylates