SEARCH

SEARCH BY CITATION

Keywords:

  • Breath test;
  • Dumping;
  • Dyspepsia;
  • Gastric emptying;
  • Gastroparesis

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

Background  The [13C]-Spirulina platensis gastric emptying breath test (GEBT) with five samples is accurate relative to scintigraphy. This study was primarily designed to further validate this GEBT using a slightly different process for incorporating [13C] in Spirulina and to evaluate the utility of additional samples for assessing early gastric emptying.

Methods  After a 223 kcal, test meal labeled with 99mTc and [13C]-S. platensis, scintigraphic images, and five breath samples (45, 90, 120, 180, and 240 min, GEBT5) were collected in 14 controls (Part A). In Part B, nine breath samples were collected at 15, 30, 45, 60, 90, 120, 150, 180, and 240 min (GEBT9) in 30 subjects (15 controls, 15 dyspepsia). Using correlation between [13C] breath excretion and scintigraphic emptying, lag time (t10, time for 10% emptying), emptying at 30 min (GE30), and half time (t50) were estimated for GEBT5 (Parts A and B) and GEBT9 (Part B).

Key Results  Half time values for scintigraphy, GEBT5, and GEBT9 were highly concordant. t10 by GEBT9 (90%CI, 6–15 min) was more strongly correlated [CCC 0.80 (95% CI, 0.63–0.90)] with scintigraphy (90% CI, 5–12 min), than GEBT5 [10–19 min, CCC 0.73 (95% CI, 0.54–0.85)]. The correlation between estimated values (GEBT9) and linearly interpolated values (GEBT5) was closer at 60 [CCC 0.95 (95% CI, 0.91–0.97)] than 30 min [CCC 0.81 (95% CI, 0.71–0.89)].

Conclusions & Inferences  The [13C]-S. platensis GEBT can accurately measure GE. While 5- and 9-samples are equally accurate for measuring t50, GEBT9 provides a more comprehensive assessment of early GE (t10 and GE30).


Abbreviations:
BT

Breath test

[13C]

13-carbon

CCC

concordance correlation coefficient

CV

coefficient of variation

DOB

delta over baseline

GE

gastric emptying

GEBT

gastric emptying breath test

GEBT5

gastric emptying breath test with 5 breath samples

GEBT9

gastric emptying breath test with 9 breath samples

PCD

percent dose

kPCD

percent dose multiplied by 1000

ROI

region of interest

[99mTc]

99m- technetium

t10

time for 10% emptying

GE30

gastric emptying in 30 min

t50

gastric emptying half time

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

Compared with current scintigraphic methods, the measurement of gastric emptying (GE) by stable isotope gastric emptying breath tests (GEBT) has practical and safety advantages. In contrast with scintigraphy, GEBT does not require elaborate detection equipment and can be performed at the point of care, as in the office or bedside because the collected breath samples are collected simply with a straw and sealable container, and the excreted 13CO2 is stable. Samples can be sent to a remote site for analysis. In addition, GEBT does not entail radiation exposure, and is safer than scintigraphy, particularly if repeated assessments are required, or, when GE needs to be assessed in pregnant or breast feeding women and in children. Our group has previously focused on developing an accurate mathematical analysis1 and reducing the number of breath samples necessary, thereby reducing the cost of the test. Using five breath samples over 3 h (i.e., before as also 45, 90, 120, and 180 min after a meal), we showed that the intra- and interindividual coefficients of variation for gastric emptying half time (t50) measured by [13C]-octanoate and [13C]-Spirulina platensis GEBT were comparable to corresponding values for scintigraphy.2–6 The most recent version of the [13C]-S. platensis GEBT uses a standardized test meal with shelf-stable components including [13C]-S. platensis7 that was validated against scintigraphy in healthy subjects, patients with accelerated and delayed gastric emptying, and healthy subjects with atropine-induced delayed gastric emptying.6 The GEBT has been endorsed by consensus statements issued by the American and European Neurogastroenterology and Motility societies.8

There is increasing recognition that rapid gastric emptying may occur not only in diabetes mellitus or after fundoplication but also in patients with functional diarrhea, functional dyspepsia, and autonomic dysfunction.9–17 We have observed that some patients with rapid early gastric emptying (e.g., at 30 or 60 min) have a normal gastric emptying t50 probably because the emptying rate slows after the initial rapid phase. It is conceivable that additional early (i.e., at 15, 30, and 60 min) and late (i.e., at 240 min) postprandial breath samples will increase the accuracy of the GEBT for identifying rapid and delayed gastric emptying relative to scintigraphy, respectively.

By growing S. platensis in a closed hydroponics chamber charged with a pure source of 13C, the cellular content of 13C is increased to 99%.7 In comparison to a previous study validating the [13C]-S. platensis GEBT,6 this study utilized a slightly modified algal growth process to enhance the yield and process efficiency. Hence, the specific aims of this study were: to (i) to estimate normal ranges for scintigraphy with this test meal; (ii) to appraise the performance characteristics (interindividual coefficients of variation (CV) of both scintigraphy and [13C]-S. platensis GEBT) in healthy volunteers; (iii) to assess the ability of the [13C]-S. platensis GEBT breath kPCD (percent dose excreted *1000) values to predict scintigraphic GE proportions at the different times, and hence to measure GE t10, GE at 30 min, and t50; (iv) to categorize GE as delayed, normal or accelerated, and (v) to ascertain whether additional early postprandial breath samples increase the accuracy of characterizing the early phase of gastric emptying.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

Experimental design

This is a report of two prospective, open-label comparison validation studies which were approved by the Mayo Clinic Institutional Review Board. In both studies, gastric emptying was simultaneously evaluated by the [13C]-S. platensis GEBT and scintigraphy. In the first study labeled, Part A, breath samples and scintigraphic images were obtained at 5 time points in 14 healthy subjects. Thereafter, we were prompted, by increasing awareness of rapid gastric emptying in our clinical practice, to assess the potential utility of collecting additional samples after the GEBT5 study was completed. Hence, breath samples and scintigraphic images were obtained at 9 specific time points in the second study (‘Part B’), in 30 participants – 15 healthy subjects and 15 patients with symptoms of dyspepsia.

Eligibility criteria for participants

Patients and healthy volunteers were recruited through public advertisement and a clinic. Participants (males and females) were aged 18–70 years and did not have clinically significant cardiovascular, respiratory, renal, hepatic, gastrointestinal, hematological, neurological, psychiatric, or other disease that may interfere with the study. Other exclusion criteria were a history of abdominal surgery other than appendectomy, cholecystectomy, tubal ligation, or hysterectomy; use of any medications that alter GI motility within 2 days of the study; any allergies to eggs, wheat, or milk or unwilling to consume such products; or receipt of an investigational drug within 30 days prior to the study. Although healthy subjects did not have symptoms of a functional GI disorder by questionnaire, patients had symptom criteria for functional dyspepsia.18 Participants were excluded if they had severe nausea or vomiting precluding study assessments; any history of malabsorption due to mucosal disease, pancreatic disease, liver dysfunction, or other causes.

Procedures

All participants had an interview and physical examination and completed questionnaires. (i.e., Hospital Anxiety and Depression Questionnaire and gastrointestinal symptom questionnaires based on Rome III criteria).18,19 Healthy subjects did not have symptom criteria for functional dyspepsia or a functional bowel disorder. Patients had Rome III symptom criteria for dyspepsia. In women of childbearing potential, a negative urine pregnancy test was required within 48 h of the gastric emptying test. After an overnight fast (minimum 8 h), the dual-label GE test was performed at the study center. Patients consumed the test meal containing 13C-Spirulina and 99mTc-sulfur colloid in no more than 10 min. Scintigraphic images and breath samples were obtained upon completion of the meal and at 45, 90, 120, 150, and 180 min after the meal in Part A or at 15, 30, 45, 60, 90, 120, 150, 180, and 240 min after the meal in Part B. In both Parts A and B, a breath sample was also collected before the test meal. Gastric images were acquired with sequential 2-min anterior and posterior images in the standing position with a single-head camera. The breath samples were collected while the posterior image was being acquired.

Test meal

The test meal consisted of 27 g freeze dried egg mix, six saltine crackers, and 180 mL of water. The caloric content of the meal is 223 kcal, and the meal has a balanced composition of 19.2 g carbohydrates, 12 g protein, and 10.9 g fat. The nature and size of the meal were selected to ensure stability at room temperature, palatability, and calorie content that would be consumed entirely, even by patients with suspected gastroparesis and upper abdominal symptoms. The meal was labeled with 0.5 mCi 99mTc-sulfur colloid and 100 mg of 13C-S. platensis, with a 13C content of 43%.

Substrate for 13CO2 Breath Test (13C-S. platensis)

Spirulina platensis is a protein-rich, blue-green algae eaten as a food source in many parts of the world, and is sold as a dietary supplement in the United States.20,21 It contains 50–60% protein, 30% starch, and 10% lipid.22 The natural level of 13C in S. platensis and in all living things is about 1%.23 The S. platensis used in this study was grown in a closed hydroponics chamber charged with pure 13C-source, raising the level of 13C in the resultant cells to 99%.7 In an attempt to enhance the yield and process efficiency, this algal growth process was slightly modified from the previous study utilizing additional culture agitation and an abbreviated harvest procedure. The 13C content and distribution of 13C-labeled protein, carbohydrate, and lipids was comparable to prior lots.6 Because the contents of the algal cells are not freely diffusible, incorporation of 13C-labeled S. platensis into the egg mix provides a way to assess the emptying of the solid phase of the meal. 13C can only be released from the algal cells after the egg mix is emptied from the stomach, the cells are digested, and the 13C-labeled substrates (algal protein, fat, and carbohydrate) are absorbed and metabolized. In this way, 13C-S. platensis gives rise to respiratory CO2 that is enriched in 13C.

Measurement of Breath 13CO2 during [13C]-S. platensis GEBT

Breath samples were taken at baseline before the meal and thereafter on the same time schedule as the scintigraphic procedures. End-tidal breath samples were collected while the participant’s abdomen was being imaged by the gamma camera. Breath samples were stored in duplicate in glass screwcap Exetainer® tubes (Labco Limited, High Wycombe, UK) using a straw to blow into the bottom of the tube to displace contained air. After recapping the tubes, the 13CO2 breath content was determined in a centralized laboratory (AB Diagnostics, Brentwood, TN, USA) by Gas Isotope Ratio Mass Spectrometry. The 13C enrichment was expressed as the delta per mL difference between the 13CO2/12CO2 ratio of the sample and the standard. To calculate the quantity of 13C appearing in breath per unit time, delta over baseline (DOB) was used where: 0.0112372 is the isotopic abundance of the limestone standard, Pee Dee Belemnite, and CO2 production was corrected for age, gender, height, and weight using the algorithms of Schofield et al., as described by Klein et al.24

Analysis of GEBT and scintigraphy data

GEBT  The currently preferred GEBT metric is the percent dose (abbreviated PCD) excreted at time t after consumption of the test meal.25 To provide a more convenient scale, we multiply PCD by 1000 to produce kPCD at any time, t.

  • image

where: DOB = The measured difference in the ratio [13CO2/12CO2] between a postmeal breath specimen at any time (t-min) and the baseline breath specimen.

CO2 PR = CO2 Production Rate (mmol CO2 min−1) calculated using Schofield equations26 which incorporate the patient’s age, gender, height, and weight.

Rs = The ratio [13CO2/12CO2] in the reference standard (Pee Dee belemnite) for these measurements, Rs = 0.0112372.

13 = the atomic weight of Carbon-13.

10 = A constant factor for converting units.

dose = the weight (mg) of Carbon-13 in the dose of [13C]-S. platensis administered to the patient in the test meal. Since [13C]-S. platensis is approximately 43% Carbon-13, a dose of 100 mg [13C]-S. platensis corresponds to approximately 43 mg of Carbon-13.

Scintigraphy  A region of interest (ROI) was drawn around the stomach on the anterior and posterior images for each time frame. Data were corrected for decay of 99mTc. To correct for depth or tissue attenuation, the counts of each anterior and posterior ROI were multiplied together and the square root of the product was taken to obtain the geometric mean. The scintigraphic GE metric, Propt, is the proportion of tracer emptied from the stomach at time, t. A linear interpolation was used to estimate the gastric emptying t50 values for each subject (i.e., linearly interpolate between the GE proportions around 0.5 to estimate the value corresponding to emptying of 50% of the meal.

Statistical methods  The individual proportions of gastric emptying at each time point and the calculated t½ values obtained from scintigraphic data in 30 subjects were summarized. The 10th and 90th percentile values in healthy volunteers for five sample and separately nine sample data were used to define normal, delayed, and accelerated GE. Because there were only 15 healthy subjects for nine sample data, more accurate estimates of 10th and 90th percentiles can be obtained than for 5th and 95th percentiles. The pairwise correlations between scintigraphic GE proportions and GEBT kPCD values were estimated.

As the generalizability of discriminant models is limited by differences in study populations, a bootstrap validation approach was used to generate a multiple linear regression model predicting the scintigraphic GE proportion at each time point (dependent variable) from GEBT kPCD values; gender and BMI were covariates. A total of 200 bootstrap samples were used to obtain a final model to predict the individual scintigraphic GE proportions at each of 9 time points using the set of 9 kPCD values (i.e., Part B) and separately, at each of 5 time points (i.e., the corresponding 5 time points from Part A and the same 5 time points in Part B).27 Including the baseline sample, a total of 6 and 10 breath samples were obtained. However, since only post baseline kPCD values were used in the models, these models are referred to as five sample and nine sample models, respectively. From the predicted GE proportions, a breath test estimate of the corresponding t50 values could be computed using the linear interpolation approach (as described above). The lag time which was estimated as the time required for 10% GE (t10), could also be estimated from the scintgraphic proportions remaining and the corresponding GEBT estimated proportions again using linear interpolation. The agreement between the scintigraphic and GEBT estimated t50 and t10 values was then assessed [Lin’s concordance correlation coefficient (CCC)]28 and a Bland–Altman plot generated to examine whether this would be a useful method to estimate gastric emptying t50 values for use in clinical practice or research. The GEBT predicted values obtained from the 9 time-point model (Part B) were compared with breath test predicted t50 values from the 5 time-point model (Parts A and B). The SAS/STAT® software package (version 9.2, SAS Institute Inc., Cary, NC, USA) was used for all statistical analyses.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

Clinical characteristics

There were 14 healthy subjects in Part A and 15 healthy subjects and 15 patients in Part B (Table 1). All patients had symptoms of dyspepsia by Rome III criteria; six had postprandial distress syndrome, two had epigastric pain syndrome, and seven had both. In addition, six had diabetes mellitus (DM; four of whom had type 2 DM), two had an autonomic neuropathy, and three had a cholecystectomy. Seven patients, including four with DM, had a history of delayed gastric emptying. Malabsorption and significant liver disease were excluded by reviewing the medical history and clinical records, respectively.

Table 1.   Demographic features
 MalesFemales
Part A (5-breath sample GEBT)
 N (Healthy subjects)59
 Median age (IQR) years29.0 (26.0, 30.6)31.9 (26.8, 41.1)
 Median body mass index (IQR) kg m−226.0 (25.1, 26.1)24.2 (23.5, 27.0)
Part B (9-breath sample GEBT)
 N (Total, healthy subjects, patients)10, 5, 520, 10, 10
 Median age (IQR) years41.5 (23.0, 52.0)46.5 (29.9, 54.0)
 Median body mass index (IQR) kg m−224.3 (22.1, 29.5)25.5 (22.8, 30.4)

The results for scintigraphy vs GEBT5 and separately for scintigraphy vs GEBT9 are presented separately and followed by a comparison of GEBT5 vs GEBT9.

Assessment of gastric emptying from healthy subjects & patients using the 5-breath sample model (Parts A and B)

In addition to all participants in Part A who had a 5-breath sample GEBT, the 5-breath sample model also incorporated the data from five selected breath samples (i.e., 45, 90, 120, 150, and 180 min) in all Part B participants, in whom nine breath samples were obtained.

Performance and correlations  Interindividual CV% for scintigraphic GE proportions and the GEBT kPCD values were, respectively, 34.5% and 39.0% at 45 min; 28.5% and 34.8% at 90 min; 24.5% and 29.4% at 120 min; 20.0% and 25.9% at 150 min; and 17.4% and 22.9% at 180 min.

Tables 2 and 3 demonstrate the excellent correlation between GE parameters by scintigraphy and the corresponding GEBT values, which establishes the strong association between these variables. In each subject, equations derived from multiple linear regression models were used to predict GE proportions from breath test kPCD values at 45, 90, 120, 150, and 180 min, including gender and BMI as covariates (Table S1). The corresponding proportions remaining in the stomach averaged across all subjects for the scintigraphic proportions and separately the breath test-estimated proportions are shown in Fig. 1.

Table 2.   Gastric emptying characteristics using 5-point model (Parts A and B)
 All subjects (N = 44)Healthy subjects only (N = 29)
ScintigraphyBreath test estimatesScintigraphyBreath test estimates
  1. Values are Mean ± SD.

T10%, min15.8 ± 7.615.01 ± 5.613.3 ± 4.012.8 ± 2.7
T ½, min82.2 ± 34.682.5 ± 33.265.9 ± 14.767.3 ± 14.0
GE 45 min0.330 ± 0.1140.329 ± 0.0910.365 ± 0.0900.366 ± 0.067
GE 90 min0.587 ± 0.1670.588 ± 0.1540.667 ± 0.1040.659 ± 0.105
GE 120 min0.719 ± 0.1760.720 ± 0.1650.809 ± 0.0990.798 ± 0.104
GE 150 min0.813 ± 0.1630.813 ± 0.1480.894 ± 0.0860.882 ± 0.086
GE 180 min0.869 ± 0.1510.868 ± 0.1330.942 ± 0.0720.927 ± 0.073
Table 3.   Correlations between proportion emptied from the stomach by scintigraphy and kPCD by [13C]-Spirulina platensis GEBT at a priori chosen time points in all participants. 5-point model
Pearson correlation coefficients, n = 44
  GE45 GE 90 GE120 GE150 GE180
  1. All correlations marked ‘*’ have a P ≤ 0.0010 and correlations marked ‘†’ have a P > 0.0 10 and ≤0.0050.

  2. BT = breath test kPCD; GE = proportion of gastric emptying at specified times.

BT450.616*0.673*0.656*0.638*0.571*
BT900.649*0.842*0.844*0.887*0.782*
BT1200.644*0.846*0.885*0.898*0.864*
BT1500.524*0.734*0.790*0.844*0.841*
BT1800.4170.610*0.656*0.752*0.787*
image

Figure 1.  Summary of gastric emptying results from the 5 time-point model in 44 subjects. Left panel illustrates mean 13CO2 enrichment of breath excreted over 3 h (right Y-axis κPCD × 10−2), as well as the mean observed proportion emptied from the stomach by scintigraphy (left Y-axis) and the mean predicted GE based on the bootstrap regression model using the measured 13CO2 excretion. The observed (scintigraphic) and predicted (GEBT) values are nearly identical; hence superimposed. Right panel illustrates scatterplot of the scintigraphic measured GE t50 values (Y-axis) vs the breath test-estimated t50 values (X-axis) obtained from linear interpolation of breath test predicted GE proportions based on the five time points model. Only data up to 180 min were used in this model. Hence, t50 was censored at 180 min in two subjects. The dotted line shows X = Y.

Download figure to PowerPoint

Estimates of gastric emptying in health and dyspepsia  The 10th and 90th percentiles for the GE t50 measured by scintigraphy in healthy volunteers were 48 and 85 min, respectively. The corresponding values for GEBT t50 values measured by the 5-point model were 51 and 91 min. The mean difference (10th, 90th percentile range) between GE t50 measured by scintigraphy and GEBT was −0.3 (−12, 14) min. For scintigraphy, the interindividual coefficient of variation for t50 was 42% (N = 44) overall, 22% in healthy subjects, and 35% in dyspepsia. The corresponding values for GEBT estimated t50 were 40%, 21%, and 36%, respectively.

Based on the scintigraphic normal values from the 5 time-point data, three patients had normal, 11 had delayed and one had rapid gastric emptying. Average scintigraphic proportions emptied for these groups and for the 14 healthy subjects studied in Part A are provided in detail in Table S2.

Accuracy assessed by concordance correlation  The (linear) concordance correlation coefficient (CCC) between the scintigraphic and GEBT estimated t50 values was 0.95 (95% CI, 0.91–0.97) for all subjects, 0.83 (95% CI, 0.67–0.92) in healthy subjects, and 0.94 (95% CI, 0.83–0.98) in patients.

Assessment of gastric emptying from healthy individuals & dyspepsia using the 9-breath sample model (Part B only)

Performance and correlations  Scintigraphic measurements and breath test samples were obtained at 9 time points (15, 30, 45, 60, 90, 120, 150, 180, and 240 min) in 30 subjects. Interindividual CV% for scintigraphic GE proportions and the GEBT9 kPCD values, respectively, were 53% and 56% at 15 min; 45% and 44% at 30 min; 38% and 42% at 45 min; 35% and 41% at 60 min; 32% and 38% at 90 min; 27% and 34% at 120 min; 22% and 31% at 150 min; 20% and 27% at 180 min; and 15% and 21% at 240 min.

Similar to the 5-sample analysis previously published,7 a multiple linear regression model approach was used to estimate gastric emptying based on the breath test samples at all 9 time points (Table S3). As in Table 2, which is based on the 5-point model, Table 4 demonstrates the excellent correlations at individual time points for scintigraphic gastric emptying values and the corresponding time kPCD values based on the 9 time-point data.

Table 4.   Correlations between proportion emptied from the stomach by scintigraphy and kPCD by [13C]-Spirulina platensis GEBT: 9-point model
Pearson correlation coefficients, n = 30
 GE15GE30 GE45 GE60 GE 90 GE120 GE150 GE180 GE240
  1. All correlations marked ‘*’ have a P ≤ 0.01 and correlations marked ‘†’ have a P > 0.01 and ≤0.05. All other correlations are >0.05. The canonical correlation analysis essentially jointly tests whether the correlations in the matrix below are simultaneously zero.

  2. BT = breath test kPCD; GE = proportion of gastric emptying at specified times.

BT150.4320.4470.4110.4230.3750.3320.3810.3170.328
BT300.4370.560*0.548*0.569*0.5111*0.494*0.493*0.4160.366
BT450.3920.675*0.664*0.688*0.639*0.621*0.598*0.516*0.455
BT600.3680.740*0.718*0.746*0.731*0.720*0.700*0.623*0.581*
BT900.4160.702*0.690*0.754*0.820*0.838*0.838*0.772*0.691*
BT1200.481*0.693*0.670*0.731*0.842*0.893*0.905*0.859*0.776*
BT1500.4390.583*0.541*0.604*0.746*0.815*0.868*0.851*0.791*
BT1800.4560.504*0.4530.511*0.663*0.725*0.821*0.835*0.801*
BT2400.2570.2760.1660.2130.3470.4180.541*0.601*0.743*

Estimates of gastric emptying in health and dyspepsia  The 10th and 90th percentiles in healthy subjects for breath test-estimated t10 values were 6 and 15 min and for breath test-estimated t50 values were 50 and 97 min. The 10th and 90th percentiles for scintigraphic GE t50 using all 9 time points in healthy volunteers were 46 and 86 min, respectively (Table 5). The mean difference (10–90th percentile range) between GE t50 measured by scintigraphy and GEBT (9-point model) was −0.7 (−13, 17) min. The interindividual CV(%) for the (9 time points) t50 values based on scintigraphy were: 53% overall, 25% in healthy volunteers, and 47% in dyspepsia. Corresponding values for GEBT9 were 46% overall, 27% in healthy subjects, and 41% in dyspepsia. Based on the scintigraphic normal values from the 9 time-point data, three patients had normal, 11 had delayed and one had rapid gastric emptying; these classifications were identical to the 5-point data.

Table 5.   Gastric emptying characteristics using 9-point model (Part B)
 All subjects (N = 30)Healthy subjects (N = 15)Dyspepsia (N = 15)
ScintigraphyBreath test estimatesScintigraphyBreath test estimatesScintigraphyBreath test estimates
  1. Values are Mean ± SD.

t10%, min13.7 ± 10.213.4 ± 9.18.8 ± 2.99.7 ± 3.618.5 ± 12.517.1 ± 11.3
t50, min93.6 ± 50.091.3 ± 42.365.9 ± 16.568.3 ± 18.2121.4 ± 57.1114.3 ± 47.3
GE 15 min0.147 ± 0.0780.145 ± 0.0580.190 ± 0.0650.171 ± 0.0490.103 ± 0.0670.120 ± 0.057
GE 30 min0.230 ± 0.1040.230 ± 0.0950.282 ± 0.0610.271 ± 0.0690.179 ± 0.1140.189 ± 0.101
GE 45 min0.324 ± 0.1230.323 ± 0.1160.386 ± 0.0860.375 ± 0.0900.262 ± 0.1260.271 ± 0.118
GE 60 min0.393 ± 0.1390.391 ± 0.1350.467 ± 0.0960.459 ± 0.1030.318 ± 0.1370.324 ± 0.131
GE 90 min0.542 ± 0.1710.540 ± 0.1650.652 ± 0.1010.641 ± 0.1140.432 ± 0.1570.439 ± 0.147
GE 120 min0.665 ± 0.1810.665 ± 0.1740.784 ± 0.1000.775 ± 0.1110.545 ± 0.1640.556 ± 0.158
GE 150 min0.765 ± 0.1720.763 ± 0.1630.873 ± 0.0960.864 ± 0.0950.656 ± 0.1630.663 ± 0.156
GE 180 min0.827 ± 0.1640.824 ± 0.1510.925 ± 0.0850.913 ± 0.0840.729 ± 0.1670.735 ± 0.151
GE 240 min0.911 ± 0.1380.903 ± 0.1180.978 ± 0.0830.958 ± 0.0470.844 ± 0.1670.847 ± 0.142

Accuracy assessed by concordance correlation  The (linear) CCC between the scintigraphic and breath test-estimated t50 values was 0.93 (95% CI, 0.86–0.96) overall, 0.94 (95% CI, 0.85–0.98) in healthy subjects, and 0.89 (95% CI, 0.72–0.96) in patients. Fig. 2 shows the plot of observed gastric emptying (mean proportions remaining in the stomach) and corresponding mean predicted proportions remaining. Also shown in Fig. 2 are the mean breath test kPCD values (*10−2).

image

Figure 2.  Summary of gastric emptying results from the 9 time-point model in 30 subjects. Data illustrate mean 13CO2 enrichment of breath excreted over 4 h (right Y-axis κPCD × 10−2), as well as the mean observed proportion emptied from the stomach by scintigraphy (left Y-axis) and the mean predicted GE based on the bootstrap regression model using the measured 13CO2 excretion. The observed (scintigraphic) and predicted (GEBT) values are nearly identical; hence superimposed. Right panel shows scatterplot of the scintigraphic measured gastric emptying t50 values (Y-axis) vs the breath test-estimated t50 values (X-axis) obtained from linear interpolation of breath test predicted GE proportions in healthy subjects and patients with dyspepsia based on the nine time-points model. The dotted line shows X = Y.

Download figure to PowerPoint

Comparison of accuracy of the 5 and 9 breath sample models

The relationship between 5- and 9-point model estimates (30 subjects in Part B) was assessed for t10, GE 30 min, and GE 60 min, which represent early gastric emptying, and t50, which summarizes the overall gastric emptying curve. Fig. 3 compares GEBT estimated t50 values from all 9 and the selected 5 time-point models (Part B). The concordance correlation between these two estimated t50 values was 0.96 (95% CI, 0.92–0.98). However, two individuals had prolonged GEBT estimated t50 values which the 5 time-point model was unable to reproduce. For these two individuals, the scintigraphic proportions indicated a t50 of at least 240 min based on 9 time points and >180 min based on 5 time points. In these subjects, the estimated t50 was 169 and 222 min by GEBT9 and 180 by min GEBT5. At the other extreme, scintigraphy disclosed rapid gastric emptying, as defined by a GE t50 shorter than the 10th percentile value, in two healthy subjects and one patient. GEBT9 also demonstrated rapid emptying in this patient and in one of these two healthy subjects. However, none of these three subjects had rapid GE by GEBT5.

image

Figure 3.  Comparison of breath test-estimated t50 values obtained from linear interpolation of breath test predicted GE proportions in healthy subjects and patients with dyspepsia based on the five time points model (X- axis) and nine time points model (Y axis). The dotted line shows X = Y.

Download figure to PowerPoint

The Bland Altman plots demonstrate that the difference between GE t50 assessed by scintigraphy and 5 point (left panel) or 9 point (right panel) breath test models was not impacted by the average t50 for both tests in the range of GE tested in these cohorts (Fig. 4).

image

Figure 4.  Bland Altman Plots for five point (left panel) and nine point (right panel) for t50 estimated by GEBT vs scintigraphy.

Download figure to PowerPoint

The 10th and 90th percentiles for t10 in healthy subjects were, respectively, 5 and 12 min by scintigraphy (9 time points), 6, and 15 min for GEBT 9-point model and 10 and 19 min for GEBT 5-point model. For t10, the CCC for scintigraphy vs GEBT 5-point and 9-point models were 0.73 (95% CI, 0.54–0.85) and 0.80 (95% CI, 0.63–0.90), respectively.

Gastric emptying at 30 and 60 min were estimated by linear interpolation between 0 and 45 min and 45 and 90 min, respectively (Fig. 5). Actual (i.e., GEBT 9-point model) and estimated values (i.e., from GEBT 5-point model) were more closely correlated at 60 min [CCC 0.95 (95% CI, 0.91–0.97)] than at 30 min [CCC 0.81 (95% CI, 0.71–0.89)].

image

Figure 5.  Comparison of actual (nine time-point data) and linearly interpolated (five time-point data) gastric emptying at 30 and 60 min by scintigraphy (left panel) and GEBT estimated proportions (right panel). The linear interpolation estimates were obtained by linear interpolation between 0 and 45 min for gastric emptying at 30 min and between 45 and 90 min for gastric emptying at 60 min.

Download figure to PowerPoint

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

The primary goals of this study were to validate a different version of a standardized, shelf-stable breath test meal labeled with [13C]-S. platensis to measure GE of solids in clinical practice, to appraise the performance characteristics of GEBT5 and GEBT9 vs scintigraphy, and to assess the accuracy of 9 compared to 5 breath samples, particularly for characterizing the early phase of GE. The study confirms previous observations obtained with a whole, fresh egg meal and with 13C GEBT in our prior studies.2–6,29 There was excellent concordance between breath excretion of 13CO2 and the proportion of isotope-labeled meal emptied from the stomach at specified time points for the 5 and separately for the 9 time-point assessments. The results confirm that the breath test provides a very valid estimate of the GE t50, which is widely used to make clinical decisions and in pharmacodynamic studies. This is supported by the observation that the concordance correlation coefficient for the GE t50 measured by scintigraphy and GEBT 5-and 9-point models averaged 0.9 and the average difference between the GE t50 calculated by scintigraphy and GEBT was less than 1 min, with a 10–90th percentile range of approximately ±15 min. Likewise, actual and linearly interpolated GE at 60 min was very similar probably because emptying is generally approximately linear between 45 and 90 min.

However, these data suggest that a GEBT with 9 time points may be preferable to a GEBT with five points for identifying rapid GE and for characterizing early GE (i.e., t10 and GE 30 min). For example, two of three subjects (one healthy subject, two patients) with rapid GE by scintigraphy also had rapid GE by GEBT9 but none had rapid GE by GEBT5. The correlation between actual (i.e., GEBT 9-point model) and estimated values (i.e., from GEBT 5-point model) for GE at 30 min was modest [CCC 0.81 (95% CI, 0.71–0.89)]. Likewise, for t10, the CCC for scintigraphy vs GEBT 5-point model was 0.73 (95% CI, 0.54–0.85) and lower than scintigraphy vs the GEBT 9-point model [0.80 (95% CI, 0.63–0.90)]. In our previous study, breath samples at 45 and 180 min had 93% sensitivity at 80% specificity for identifying rapid GE as defined by the scintigraphic t50.6 However, it is conceivable that an assessment of GE at 30 min may be more useful for identifying some patients with accelerated GE, i.e., those in whom GE is accelerated at 30 min but plateaus later, resulting in a normal t50. Because few patients had rapid GE in this study, further studies are necessary to evaluate the utility of measuring t10, and GE at 30 min by the 9 time-point model in patients with rapid GE.

Moreover, although the vast majority of asymptomatic individuals emptied the meal from the stomach before 80 min, the 240-min observation may be useful, particularly when GE is delayed. For example, when the 5 time-point model suggests a t50 > 180 min, the 240-min sample is necessary to clarify whether the t50 is closer to 180 min or even >240 min, as was observed in two patients.

In summary, the current data confirm that the stable isotope technology developed in earlier studies is also applicable with a meal in which a slightly modified process was used to enrich S. platensis with 13C. The [13C]-S. platensis GEBT has high reproducibility, external validity and excellent performance characteristics. The statistical models previously proposed, based on linear regression, continue to demonstrate that they are robust to estimate GE in health and disease, and offer further support for the use of this GEBT in clinical practice, epidemiological studies, or clinical research studies. A 5-sample test is as accurate as a 9-point test for identifying normal GE in symptomatic patients. The 9-breath sample test is more accurate for evaluating early GE (e.g., t10 and GE at 30 min), which is accelerated in patients with rapid GE, and provides a more comprehensive assessment in some patients with delayed GE. Further studies need to fully address the relative accuracy of the 5- and 9-point models in patients with rapid GE.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

This study was supported by PO1 DK 68055 from National Institutes of Health. The studies were conducted in the Mayo Clinic Clinical Research Unit which is supported by grant RR024150 from National Institutes of Health.

AB Diagnostics provided breath test kits at cost price and analyzed breath samples without charge but did not support the study in any other manner.

Author contributions

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

Adil E. Bharucha was principal investigator for the study and contributed to study design and concept, data analysis and interpretation, and manuscript preparation, critical revision, and final approval. Michael Camilleri contributed to study design and concept and critical revision of manuscript. Erica Veil and Duane Burton contributed to study conduct. Alan R. Zinsmeister conducted data analysis and critically revised the manuscript. All authors approved the final version of the manuscript.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information
  • 1
    Odunsi ST, Camilleri M, Szarka LA, Zinsmeister AR. Optimizing analysis of stable isotope breath tests to estimate gastric emptying of solids. Neurogastroenterol Motil 2009; 21: 706e38.
  • 2
    Choi MG, Camilleri M, Burton DD, Zinsmeister AR, Forstrom LA, Nair KS. [13C]octanoic acid breath test for gastric emptying of solids: accuracy, reproducibility, and comparison with scintigraphy. Gastroenterology 1997; 112: 115562.
  • 3
    Choi MG, Camilleri M, Burton DD, Zinsmeister AR, Forstrom LA, Nair KS. Reproducibility and simplification of c-13-octanoic acid breath test for gastric emptying of solids. Am J Gastroenterol 1998; 93: 928.
    Direct Link:
  • 4
    Lee JS, Camilleri M, Zinsmeister AR et al. Toward office-based measurement of gastric emptying in symptomatic diabetics using [13C]octanoic acid breath test. Am J Gastroenterol 2000; 95: 275161.
    Direct Link:
  • 5
    Lee JS, Camilleri M, Zinsmeister AR, Burton DD, Kost LJ, Klein PD. A valid, accurate, office based non-radioactive test for gastric emptying of solids. Gut 2000; 46: 76873.
  • 6
    Szarka LA, Camilleri M, Vella A et al. A stable isotope breath test with a standard meal for abnormal gastric emptying solids in the clinic and in research. Clin Gastroenterol Hepatol 2008; 6: 63543.
  • 7
    Advanced Breath Diagnostics L. [13C]-Spirulina Platensis Gastric Emptying Breath Test (GEBT)-Investigator Brochure. Brentwood, TN, 2005.
  • 8
    Abell TL, Camilleri M, Donohoe K et al. Consensus recommendations for gastric emptying scintigraphy: a joint report of the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine.[reprint in J Nucl Med Technol. 2008;36(1):44-54; PMID: 18287197]. Am J Gastroenterol 2008; 103: 75363.
    Direct Link:
  • 9
    Charles F, Phillips SF, Camilleri M, Thomforde GM. Rapid gastric emptying in patients with functional diarrhea. Mayo Clin Proc 1997; 72: 3238.
  • 10
    Weytjens C, Keymeulen B, Van Haleweyn C, Somers G, Bossuyt A. Rapid gastric emptying of a liquid meal in long-term Type 2 diabetes mellitus. Diabet Med 1998; 15: 10227.
  • 11
    Delgado-Aros S, Camilleri M, Cremonini F, Ferber I, Stephens D, Burton DD. Contributions of gastric volumes and gastric emptying to meal size and postmeal symptoms in functional dyspepsia.[see comment]. Gastroenterology 2004; 127: 168594.
  • 12
    Lawal A, Barboi A, Krasnow A, Hellman R, Jaradeh S, Massey BT. Rapid gastric emptying is more common than gastroparesis in patients with autonomic dysfunction. Am J Gastroenterol 2007; 102: 61823.
  • 13
    Bharucha AE, Camilleri M, Forstrom L, Zinsmeister AR. Relationship between clinical features and gastric emptying disturbances in diabetes mellitus. Clin Endocrinol (Oxf) 2008; 70: 41520.
  • 14
    Malhotra N, Pathikonda M, Sachdeva P, Maurer AH, Fisher RS, Parkman HP. Rapid gastric emptying or gastroparesis: can one tell the difference in the clinic? Gastroenterology 2010; 138: W1388.
  • 15
    Hejazi RA, Patil H, McCallum RW. Dumping syndrome: establishing criteria for diagnosis and identifying new etiologies. Dig Dis Sci 2010; 55: 11723.
  • 16
    Bharucha AE, Manduca A, Lake DS et al. Gastric motor disturbances in patients with idiopathic rapid gastric emptying. Neurogastroenterol Motil 2010; 23: 617e252.
  • 17
    Balan K, Sonoda LI, Seshadri N, Solanki C, Middleton S. Clinical significance of scintigraphic rapid gastric emptying. Nucl Med Commun 2011; 32: 11859.
  • 18
    Tack J, Talley NJ, Camilleri M et al. Functional gastroduodenal disorders.[erratum appears in Gastroenterology. 2006 Jul;131(1):336]. Gastroenterology 2006; 130: 146679.
  • 19
    Longstreth GF, Thompson WG, Chey WD, Houghton LA, Mearin F, Spiller RC. Functional bowel disorders. Gastroenterology 2006; 130: 148091.
  • 20
    Ciferri O. Spirulina, the edible microorganism. Microbiol Rev 1983; 47: 55178.
  • 21
    Ciferri O, Tiboni O. The biochemistry and industrial potential of Spirulina. Annu Rev Microbiol 1985; 39: 50326.
  • 22
    Dillon JC, Phuc AP, Dubacq JP. Nutritional value of the alga Spirulina. World Rev Nutr Diet 1995; 77: 3246.
  • 23
    Ricci E. Determination of carbon-12, carbon-13 isotopic abundances and nitrogen-carbon ratios in biological substances by proton-reaction analysis. Anal Chem 1971; 43: 186671.
  • 24
    Klein PD. Clinical applications of 13CO2 measurements. Fed Proc 1982; 41: 2698701.
  • 25
    Schoeller DA, Schneider JF, Solomons NW, Watkins JB, Klein PD. Clinical diagnosis with the stable isotope 13C in CO2 breath tests: methodology and fundamental considerations. J Lab Clin Med 1977; 90: 41221.
  • 26
    Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Human Nutr Clin Nutr 1985; 39(Suppl. 1): 541.
  • 27
    Barrett TW, Martin AR, Storrow AB et al. A clinical prediction model to estimate risk for 30-day adverse events in emergency department patients with symptomatic atrial fibrillation. Ann Emerg Med 2011; 57: 112.
  • 28
    Carrasco JL, Jover L. Estimating the generalized concordance correlation coefficient through variance components. Biometrics 2003; 59: 84958.
  • 29
    Viramontes BE, Kim DY, Camilleri M et al. Validation of a stable isotope gastric emptying test for normal, accelerated or delayed gastric emptying. Neurogastroenterol Motil 2001; 13: 56774.

Supporting Information

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Funding
  9. Disclosure
  10. Author contributions
  11. References
  12. Supporting Information

Table S1. Predicted Gastric Emptying Proportions at Different Time Points Based on Gender, BMI, and 13CO2 Excretion at Specified Times for 5 Point Model

Table S2. Summary of Gastric Emptying Results by t50 (scintigraphy) in 44 subjects (29 healthy, 15 dyspepsia)

Table S3. Predicted Gastric Emptying Proportions at Different Time Points Based on Gender, BMI, and 13CO2 Excretion at Specified Times for 9 POINT MODEL

FilenameFormatSizeDescription
NMO_12054_sm_TableS1-S3.docx16KSupporting info item

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.