A valid, accurate, office based non-radioactive test for gastric emptying of solids

Abstract

Background: Current breath tests for measurement of gastric emptying of solids are expensive, possibly inaccurate, and require cumbersome calculations.

Aims: We wished to validate a simplified solid gastric emptying test using a [(13)C]Spirulina platensis breath test for accurate results relative to scintigraphy.

Subjects: Thirty healthy volunteers.

Methods: We measured gastric emptying of egg containing [(13)C]S platensis and (99m)Tc sulphur colloid by breath (13)CO(2) and scintigraphy over six hours. A generalised linear regression model was used to predict t(1/2) and t(LAG) by scintigraphy from breath (13)CO(2) data. The model was cross validated and normative data calculated for a prepacked [(13)C]meal.

Results: Regression models using all breath data over six hours, for the first three hours, and for samples at 75, 90, and 180 minutes ("reduced model") predicted t(1/2) and t(LAG) values similar to scintigraphy (t(LAG) 43 (SD 12) min; t(1/2) 100 (20) min). Standard deviations of differences in t(1/2) and t(LAG) between scintigraphy and the "reduced model" were both 10 minutes. Gastric t(1/2) for the prepacked [(13)C]meal was 91 (15) min (10-90% range: 74-118).

Conclusion: The [(13)C]S platensis breath test and a simple formula using breath (13)CO(2) at baseline, 90, and 180 minutes measured gastric emptying t(1/2) for solids with results that were comparable with scintigraphy.

Figure 1

Association between lag phases (t_LAG ) and half-emptying times (t_1/2) for scintigraphy values compared with estimates from a generalised linear regression model based on breath test values from the first three hours of data (A, B) and for two time points from the first three hours of sampling (C, D; the y=x line is shown for comparison). Note the significant correlation between estimates. The variation in differences between estimates by the two methods is expressed as SD_Δ and range.

Figure 2

Comparison of gastric lag phase duration (t_LAG) (A) and half-emptying times (t_1/2) (B) from scintigraphy and [¹³C]S platensis breath tests using the generalised linear regression models (GLM), shown as median values (bars), interquartile ranges (boxes), range from 10th to 90th percentiles (bar caps), and practical data over the 10th to 90th percentiles (dots) for scintigraphy and breath tests. Note the excellent agreement between scintigraphy and generalised linear models.

Figure 3

Cross validation results for generalised linear regression reduced model using the leave-one-out approach. Note the significant correlation between estimates. The variation in differences between estimates by the two methods is expressed as SD_Δ and range. Cross validated estimate of the differences between scintigraphic t_1/2 and estimated t_1/2 from the reduced model using three time points from the breath test had a standard deviation of 13 minutes (−29 to 31) while that for t_LAG was 11 minutes (−23 to 23).

Figure 4

Distribution of t_LAG (A) and t_1/2 (B) using [¹³C]S platensis in an egg meal and in a biscuit meal in 27 healthy subjects, shown as median values (bars), interquartile ranges (boxes), range from 10th to 90th percentiles (bar caps), and observed data over 10th to 90th percentiles (dots). Note the good agreement between results from the two meals.