Carbon-13 (13C)-Spirulina Platensis Gastric Emptying Breath Test (GEBT): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Carbon-13 (13C)-Spirulina Platensis Gastric Emptying Breath Test (GEBT) (NCT01248221), a non-randomized na study. The primary outcome is Gastric Emptying Half Time Measured by Scintigraphy.

2. Clinical Question

The study’s stated purpose is to compare stomach emptying measured by the 13C-Spirulina breath test and by scintigraphy in healthy subjects and subjects with dyspepsia. The same standard meal is labeled with both tracers, permitting the two measurement approaches to be used after that meal. Scintigraphy tracks the meal through images of the 99mTc sulfur colloid, while breath samples measure the presence of 13C.

The primary endpoint is gastric emptying half time measured by scintigraphy. The record also lists secondary assessments of gastric emptying at 60, 120, and 240 minutes, measured by scintigraphy and by the breath test. The central statistical question is therefore about measurement: how the breath-test readings relate to the scintigraphic assessments in the two groups. However, the registry record does not report outcome values, estimates of the relationship between methods, or results separately for either population. It is not possible to determine from the registry record how closely the methods agreed or whether their results differed between the groups.

3. Trial Design

This is a completed, non-randomized, parallel study with no masking. The registry lists an enrollment of 30 and describes two groups: healthy subjects and dyspeptic subjects. Group membership is based on the population being studied, not on random assignment to competing treatments. Accordingly, these groups should not be read as randomized treatment arms or as a like-for-like control comparison.

Participants consumed a standard meal of scrambled eggs, wheat toast, and skim milk. The eggs were labeled with both 99mTc sulfur colloid and 13C-Spirulina platensis. Scintigraphy used images of the radioactive tracer to assess the location of the meal in the digestive system; the breath test measured 13C in breath samples. The design thus permits both measurement methods to be used following the same meal. The registry describes the primary scintigraphy endpoint as measured 4 hours after meal ingestion and lists secondary measurements at 60, 120, and 240 minutes.

The record identifies the sponsor as Mayo Clinic, gives the study start as 2010-12 and primary completion as 2011-12, and marks the study completed. The phase is listed as NA. The registry does not report how participants were recruited, the eligibility criteria in detail, or the allocation procedures beyond identifying the study as non-randomized. It also does not report a masking procedure; masking is listed as none. The groups and measurement methods support a descriptive or measurement-comparison question, but the design does not establish a randomized causal comparison between healthy and dyspeptic participants.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Gastric Emptying Half Time Measured by Scintigraphy, measured over 4 hours after ingestion of standard meal.

The primary endpoint is gastric emptying half time measured by scintigraphy, in minutes, over the timeframe described as 4 hours after ingestion of the standard meal. Half time is defined in the registry as the time for half of the ingested solids to leave the stomach. The measurement uses standard 99mTc scintigraphy, in which images track the labeled meal through the digestive system.

Half time expresses gastric emptying as a continuous measure of elapsed time. A mean can describe the group’s average measured half time, while a standard deviation describes the spread of individual measurements around that mean. These are descriptive summaries, not measures of how closely the breath test agrees with scintigraphy. The registry record identifies the endpoint’s summary as a mean with standard deviation but does not report the resulting mean or standard deviation.

The endpoint is relevant to the study’s stated measurement question because scintigraphy is one of the two methods being compared. The registry also lists secondary assessments at 60, 120, and 240 minutes using scintigraphy and the 13C-Spirulina gastric emptying breath test. Those time-specific assessments can describe emptying at particular points after the meal, but their values and any comparisons between methods are not reported in the registry record. The primary endpoint alone cannot establish the breath test’s agreement with scintigraphy; that requires reported results from both methods and an analysis appropriate to the intended comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record identifies a continuous primary endpoint summarized as a mean and standard deviation. It does not report numerical endpoint results or a statistical analysis plan. The explanations below describe general statistical ideas relevant to this kind of study; they should not be read as a claim that a particular analysis was performed.

What does a mean describe?

In general, the mean is an average of the observed measurements in a group. For gastric emptying half time, the measurements are elapsed times in minutes. The mean can provide a concise description of the group’s central value, but it does not show whether participants’ measurements are tightly clustered or widely spread. The standard deviation describes that spread: a larger standard deviation indicates more variability among observed measurements relative to the group mean. Neither statistic alone describes uncertainty in the estimated mean.

How is uncertainty about an estimate expressed?

In general, a confidence interval gives a range of values compatible with the observed data under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, while the interval’s location indicates which values remain plausible. A confidence interval is not a guarantee that the true value lies in the particular interval. The registry record does not report confidence intervals for the primary endpoint or for a comparison between measurement methods, so the precision of any such estimate cannot be assessed.

A p-value, in general, measures how incompatible the observed data are with a specified null hypothesis under the assumptions of a statistical test. It is not the probability that the null hypothesis is true, and it does not measure the practical importance or precision of an effect. No p-value or statistical test result is reported for the primary endpoint in the registry record. Therefore, there is no posted hypothesis-test result to interpret.

What does a comparison of measurement methods require?

General method-comparison analysis distinguishes association from agreement. Association describes whether measurements tend to vary together; agreement asks how close the methods’ readings are, including whether one method tends to read systematically higher or lower and how large individual differences can be. Two methods can be strongly associated while differing enough that their readings are not interchangeable. The study’s use of both tracers in the same meal creates a basis for comparing readings, but the registry does not report a method-comparison estimate, a plot of paired differences, or the analysis used to evaluate agreement.

Because each meal is assessed using both scintigraphy and breath testing, the resulting measurements may be related within a participant. In general, an analysis that compares methods should account for that pairing rather than treating all measurements as independent. The exact participant-level data structure and analysis are not reported in the registry record. It is therefore not possible to determine whether the posted analysis, if any, accounted for the relationship between measurements from the same participant.

Why does the non-randomized design matter?

In general, randomization helps balance measured and unmeasured characteristics between assigned groups. Here, the groups are healthy subjects and dyspeptic subjects, and the study is identified as non-randomized. A contrast between these populations would describe differences observed between groups; it would not by itself isolate the effect of dyspepsia or establish causation. Differences in other participant characteristics could influence measurements. The registry record does not report an adjusted model or covariates used to address such differences.

Similarly, the record states that masking was none. In general, knowledge of a group or measurement method can influence aspects of assessment or interpretation, depending on how measurements are collected and processed. The record does not describe procedures to reduce such influence. This does not establish that bias occurred; it means that the registry record does not provide enough detail to evaluate masking-related safeguards.

What do planning calculations mean?

In general, a sample-size calculation is a planning exercise based on assumptions about the effect to detect, variability, allocation, significance level, and desired power. The registry’s stated assumptions describe an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as a stated fraction of the observed effect. Such an illustration is not an analysis of the completed study’s ability to detect an effect and is not observed power. The registry record does not report the study’s own sample-size justification. Any planning illustration should be understood as conditional on its assumptions, not as evidence that an effect was observed or that the study had a particular probability of finding it.

The reported enrollment and the number of measurements available for analysis are different concepts. Enrollment describes the record’s stated study size; an analysis may include fewer observations if data are unavailable or excluded. The registry record does not report analysis populations, exclusions, or missing measurements. Those omissions limit interpretation of both descriptive summaries and any hypothetical inferential comparison.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Healthy Subjects", "Dyspeptic Subjects")
n   <- c(15, 15)
m   <- c(65.9, 82.2)
sp  <- c(14.7, 34.6)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Healthy Subjects  15  65.900  14.700  57.759  74.041
CARM  Dyspeptic Subjects  15  82.200  34.600  63.039  101.361

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary endpoint of gastric emptying half time measured by scintigraphy. It also lists secondary outcomes for gastric emptying at 60, 120, and 240 minutes, measured by scintigraphy and by the 13C-Spirulina gastric emptying breath test. The record identifies four outcome measures, but does not report their numerical results or the analyses performed.

When a study examines multiple outcomes or makes multiple statistical comparisons, the chance of at least one apparently notable result can increase. General approaches to multiplicity include specifying a primary analysis in advance, adjusting inference across tests, or interpreting secondary analyses as exploratory. The registry record does not report whether multiplicity was addressed, what testing hierarchy was intended, or whether any adjustment was used. No specific correction or analysis should be inferred.

Missing-data handling is also not reported in the registry record. The record does not state whether all enrolled participants completed measurement, whether any measurements were missing, how missing values were handled, or whether sensitivity analyses were conducted. The analysis populations and the number of participants contributing to each endpoint are not reported. The group counts in the safety listing do not establish the analysis denominators for the gastric-emptying outcomes.

The registry record also does not report an analysis plan, interim analyses, or a sample-size justification for the completed study. The absence of those details does not establish which procedures were or were not used outside the record; it means they cannot be evaluated from the registry information. Without outcome-specific denominators and missing-data methods, the completeness of the reported outcome evidence cannot be assessed.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The registry lists serious adverse events for the healthy-subject group and the dyspeptic-subject group. Each group has 15 subjects listed as at risk, and zero serious adverse events are listed in each group. The record also lists zero other adverse events in each group, with 15 subjects at risk for that category. These are the event counts recorded in the registry; they are not estimates of the frequency of events beyond the listed study groups.

Zero recorded events should be read as an absence of events listed in this record, not as proof that an event is impossible or that the intervention is risk-free. Safety summaries depend on the period of observation, how events were collected, and which events were included. The registry record does not provide additional detail about those procedures or a narrative of adverse-event monitoring.

Deaths are not reported in the registry record. The safety listings also do not provide a comparison of event rates between randomized groups, because the study was non-randomized and the groups represent healthy and dyspeptic subjects. The listed counts should therefore be interpreted descriptively rather than as evidence of a causal safety difference.

13. What the Result Does, and Does Not, Mean

The registry record describes a study designed to compare two ways of assessing gastric emptying: scintigraphy and a 13C-Spirulina breath test. It identifies healthy subjects and subjects with dyspepsia as the study populations, describes a meal labeled for both methods, and names scintigraphic gastric emptying half time as the primary endpoint. This defines the research question and broad measurement approach.

What the record does not provide is the observed endpoint value or a numerical comparison of the methods. It does not report whether the breath test and scintigraphy produced similar readings, whether either method tended to give higher readings, or how much individual measurements differed. It therefore cannot establish from the posted results whether the breath test agrees with scintigraphy in this study. The record also does not provide an estimate of differences between healthy and dyspeptic subjects.

In general, demonstrating that two methods are associated is not the same as showing that they agree closely enough for a particular purpose. A useful evaluation of measurement agreement ordinarily requires reported paired measurements or appropriate summaries of their differences, together with uncertainty and enough methodological detail to interpret the comparison. Those results and details are not reported in the registry record.

The non-randomized design also limits the interpretation of contrasts between the two population groups. If their measurements differed, that finding would be an observed difference between groups, not a randomized causal effect. The record does not report adjustments that might address differences in participant characteristics.

Thus, the study’s registered objective and endpoint can be described, but its empirical findings cannot be judged from the registry record. The absence of posted outcome analyses is not evidence that the two methods are equivalent or different. It means that the statistical evidence needed to assess either conclusion is not reported.

14. Why This Trial Matters Statistically

This study raises a practical statistical issue: a new measurement method must be evaluated against the method used as its comparator, and the question is not answered merely by collecting readings from both. Researchers need to distinguish whether measures are associated from whether they agree closely, and to report the size and precision of any differences. That distinction is central to interpreting a breath-based measure alongside scintigraphic assessment.

The use of a meal labeled with both 13C-Spirulina platensis and 99mTc sulfur colloid is relevant to this measurement question because the two approaches assess gastric emptying following the same meal. The registered outcomes include a scintigraphic half time and assessments at specified post-meal times using both methods. However, the registry record does not report the results needed to evaluate the comparison. The statistical importance of the design therefore cannot be translated into a conclusion about measurement performance.

The study also illustrates why population comparisons require care. Healthy subjects and subjects with dyspepsia are distinct groups, not randomized treatment assignments. A contrast between them may be informative descriptively, but it cannot by itself show that group status caused any difference. Reporting participant characteristics and appropriate adjusted analyses can help readers assess possible alternative explanations; those details are not reported in the registry record.

Finally, a complete statistical account needs more than an endpoint label and an enrollment figure. Outcome summaries, uncertainty, analysis populations, missing-data handling, and the method-comparison strategy are needed to judge what the measurements establish. The registry record leaves those elements unreported. Its statistical value lies in clarifying the planned measurement question and in showing the limits of what can be concluded without posted results.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The most direct limitation of the registry record is that it does not report outcome values or analyses. The primary endpoint is defined, but its mean and standard deviation are not reported. Nor are there confidence intervals, p-values, or estimates comparing breath-test readings with scintigraphy. As a result, the size, direction, and precision of any measurement differences cannot be assessed.

The study is non-randomized, and the two groups are healthy subjects and subjects with dyspepsia. They are not randomized controls for one another. Any group contrast could reflect differences in participant characteristics as well as differences associated with dyspepsia. The registry record does not report detailed eligibility criteria, participant characteristics, or adjusted analyses that could help readers evaluate this issue.

The record identifies no masking. It does not describe whether measurement processing or interpretation used safeguards against knowledge of group or method. The exact analysis used to compare the measurement methods is also not reported. In particular, the record does not state how agreement, paired measurements, or repeated observations were handled.

Outcome-specific analysis denominators, missing-data procedures, exclusions, and analysis populations are not reported. The safety denominators do not establish which participants contributed to each gastric-emptying outcome. The record also does not report the study’s own sample-size justification or a statistical analysis plan. These omissions limit assessment of design adequacy, analytic choices, and the completeness of the evidence. They do not establish that particular methods were absent from study conduct; they identify information not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Carbon-13 (13C)-Spirulina Platensis Gastric Emptying Breath Test (GEBT) — NCT01248221.
• Registry record last updated 2013-03-18; status last verified 2013-02.
• Results first posted 2013-03-18.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT01248221 is a completed, non-randomized, unmasked, parallel study sponsored by Mayo Clinic. It lists an enrollment of 30 and includes healthy subjects and subjects with dyspepsia. The study compared gastric emptying assessment using scintigraphy and a 13C-Spirulina breath test after a standard meal labeled with 13C-Spirulina platensis and 99mTc sulfur colloid.

The primary endpoint is gastric emptying half time measured by scintigraphy, summarized as a mean with standard deviation, with a timeframe of 4 hours after meal ingestion. Secondary outcomes include gastric emptying at 60, 120, and 240 minutes measured by scintigraphy and by the breath test. The registry record does not report outcome values or analyses, so the comparison between methods cannot be evaluated from the posted results.