Pharmacokinetics Study of Dipeptidyl Peptidase 4 Inhibitor to Control Type 2 Diabetes Mellitus: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacokinetics Study of Dipeptidyl Peptidase 4 Inhibitor to Control Type 2 Diabetes Mellitus (NCT01449747), a non-randomized phase 4 study. The primary outcome is Plasma Concentration of Active Glucagon-like Peptide 1 (GLP-1) Before and After Sitagliptin Treatment.

2. Clinical Question

The study’s stated purpose was to investigate a mechanism of reduced response to a DPP-4 inhibitor in some patients with type 2 diabetes and to evaluate which patients might be appropriate to treat with a DPP-4 inhibitor. The registry record lists a secondary outcome concerning differences in DPP-4 activity after sitagliptin treatment between responder and non-responder groups. It does not report the criteria used to define response, the findings for that secondary outcome, or a statistical estimate answering the primary question. Consequently, the study question can be described, but its answer cannot be determined from the posted results.

3. Trial Design

This is a Phase 4, non-randomized, parallel-group study of sitagliptin. The registry record lists no masking. Its stated enrollment is 24, and the arm descriptions identify a study group of sitagliptin hypo-response patients and a control group of sitagliptin response patients. The safety record lists 12 participants at risk in each group. Because participants were grouped by response status rather than randomized to contrasting treatments, the groups should not be treated as exchangeable treatment arms.

The registry record lists the study start as 2011-12 and primary completion as 2014-08, with a completed status. The sponsor is The Catholic University of Korea. These administrative details describe the registered study; they do not establish when any particular measurement occurred beyond the outcome timeframe stated in the record.

The primary outcome is a continuous measure: mean plasma concentration of active GLP-1, with standard deviation as the stated dispersion. Measurements are specified at 0, 15, 30, 45, 60, 90, 120, and 180 min during a meal tolerance test before treatment and during a second meal tolerance test after participants took sitagliptin 100 mg 1 hour before the test. The registry record lists five outcome measures but does not provide their numerical results. It lists no analyses.

The non-randomized design matters for interpretation. Differences between responder and hypo-responder groups could reflect how those groups came to be defined or other group differences; the registry record does not provide information that would establish otherwise. The treatment-related measurements may describe biomarker patterns, but this design and record do not provide a randomized estimate of the effect of sitagliptin compared with an alternative treatment or no treatment.

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 Plasma Concentration of Active Glucagon-like Peptide 1 (GLP-1) Before and After Sitagliptin Treatment, measured over 0, 15, 30, 45, 60, 90, 120, 180 min pre and post-dose.

The primary endpoint is the mean plasma concentration of active glucagon-like peptide 1 (GLP-1), measured in pmol/L. The record specifies measurements during a meal tolerance test at 0, 15, 30, 45, 60, 90, 120, and 180 min, both before and after sitagliptin treatment. For the post-treatment assessment, participants took sitagliptin 100 mg 1 hour before the test. Standard deviation is the registered measure of dispersion.

As a biological measurement, active GLP-1 concentration can describe how this hormone’s measured level changes over the course of the meal tolerance test and whether the observed pattern differs between the response groups. That makes it relevant to the study’s stated interest in the mechanism of reduced response to a DPP-4 inhibitor. The endpoint is a biomarker measurement, not itself a clinical outcome such as symptoms, complications, or quality of life.

In general, a mean represents the average measurement in a group, while a standard deviation describes how dispersed individual measurements are around that mean. They answer different questions: the mean describes the group’s central level, and the standard deviation describes variability among measurements. Neither alone establishes whether a change is statistically distinguishable from chance or whether it is clinically important. The registry record does not report the means, standard deviations, or a statistical comparison for this endpoint, so the magnitude, direction, and precision of any observed pattern cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the primary measure as a continuous outcome summarized by a mean and standard deviation. It specifies a series of active GLP-1 measurements during meal tolerance testing before and after sitagliptin treatment. The record lists no analyses, so it does not identify the statistical procedure used to compare time points, treatment periods, or response groups. The following explains general statistical concepts relevant to this design; it does not describe methods confirmed as having been used in this study.

What does a mean and standard deviation describe?

In general, a mean gives the arithmetic average of observed measurements in a group. A standard deviation describes how spread out those observations are around the mean. A small standard deviation indicates that observations cluster more closely around the group mean; a larger one indicates more variability. The standard deviation is not the same as the standard error, which describes the precision of an estimated mean, and it is not a confidence interval. The registry record does not give the endpoint means or standard deviations, so these summaries cannot be interpreted for this study.

Why does repeated measurement matter?

In general, repeated measurements taken from the same participant are correlated: a person’s measurements over time are not independent observations. An analysis that treated every measurement as unrelated could misrepresent the uncertainty of estimated differences. Methods for repeated measurements can account for within-person dependence and estimate changes over time or differences in patterns between groups. The appropriate specification depends on the question, measurement structure, and assumptions. The statistical method and model details are not reported in the registry record.

The endpoint lists measurements at 0, 15, 30, 45, 60, 90, 120, and 180 min, with a pre-treatment and post-treatment assessment. A statistical analysis could, in general, focus on change at a particular time, an overall treatment-period contrast, or the pattern across times. Those choices answer different questions and can produce different estimates. The registry record does not specify which contrast was intended or tested. It also does not report whether the outcome was analyzed separately at each time or through a joint repeated-measures model.

What would an estimate and confidence interval add?

In general, an estimate quantifies a contrast, such as a difference in means, while a confidence interval conveys the precision compatible with the data under the model. A narrower interval indicates greater precision than a wider interval, but an interval’s interpretation also depends on the analysis assumptions and the outcome’s context. A p-value, when used, describes how compatible the observed data are with a specified null hypothesis under a statistical model; it does not measure the probability that the null hypothesis is true. The registry record reports no estimate, confidence interval, or p-value for the primary endpoint, so neither statistical significance nor precision can be evaluated.

How should the planning illustration be read?

The record’s sample-size assumptions describe a planning illustration computed from the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study was designed using them. The record does not report the trial’s own sample-size justification. Sample-size calculations are planning illustrations, not observed power, and do not establish that a result is precise or that a study has answered its question. No numerical planning estimates are reported in the registry record.

The record’s planning description distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. The primary outcome is continuous, not time-to-event. No event-time endpoint or corresponding analysis is identified in the registry record. Because no numerical primary results or analysis details are reported, the planning assumptions cannot substitute for an observed estimate and its uncertainty.

What does over-dispersion mean in general?

Over-dispersion is a general issue for count outcomes when their variability exceeds what a simple statistical model assumes. It can lead to uncertainty estimates that are too small if ignored. The primary endpoint in this record is continuous, and no count-model analysis is described. Over-dispersion therefore cannot be identified as a reported issue in this study. More generally, model assumptions should be matched to the outcome and study design, and checked where data allow; the registry record does not report such checks.

Finally, a non-randomized comparison requires cautious interpretation. In general, statistical adjustment can account for measured differences under specified assumptions, but it cannot guarantee removal of bias from unmeasured differences. The registry record does not identify adjustment variables or an adjusted analysis. It also does not report enough information to assess model fit, missing measurements, or robustness to alternative analyses.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists five outcome measures, including the primary active GLP-1 measure and a secondary outcome concerning DPP-4 activity after sitagliptin treatment between responder and non-responder groups. It lists no analyses. A statistical plan for handling multiple outcomes or multiple comparisons is not reported in the registry record.

In general, testing many outcomes, time points, or contrasts can increase the chance of obtaining at least one apparently unusual result even when there is no underlying difference. Researchers may address this by defining a primary contrast in advance, adjusting significance thresholds, or interpreting related estimates together. These approaches involve choices that should be clear to readers. The record does not say whether any such approach was prespecified or used. Because outcome values and analyses are not reported, the impact of multiplicity on interpretation cannot be assessed.

The primary endpoint entails measurements at multiple time points and before and after treatment, which creates possible choices about which time points or patterns to compare. The registry record does not identify the planned primary contrast among these measurements. It also does not say whether all registered outcomes were analyzed or whether results were omitted. Such details are not reported in the registry record.

Missing-data procedures and analysis populations are not reported in the registry record. The record does not describe how missing measurements, withdrawals, or incomplete meal tolerance tests were handled, nor does it state which participants were included in any efficacy analysis. The enrollment is listed as 24, and the safety record lists 12 participants at risk in each response group; these entries do not establish the number with complete primary outcome data. Without participant flow and analysis-population details, the extent and handling of missing outcome data cannot be evaluated.

11. 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 0% reporting threshold.

The registry safety figures list 12 participants at risk in the Non-responder group and 12 in the Responder group. For each group, the record lists 0 serious adverse events and 0 other adverse events. These figures describe the counts entered in the registry safety record; they do not establish that no adverse events occurred outside the categories or collection reflected in that record.

The death entries are null for both groups. Deaths are therefore not reported in the registry record; a null entry should not be read as a count of zero. The record lists no serious adverse event terms. It does not provide further detail on event definitions, observation duration, severity, relatedness to sitagliptin, or the process used to collect adverse events. Those details are not reported in the registry record.

Safety counts are descriptive. With no additional information about follow-up, ascertainment, or event reporting, zero listed events cannot establish the absence of risk. These registry entries also do not provide a randomized safety comparison, because the study is non-randomized and groups are classified by response status.

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

The registry record establishes that this completed Phase 4 study examined active GLP-1 concentrations before and after sitagliptin treatment in groups described as responders and hypo-responders. The primary outcome was a continuous biomarker measured during meal tolerance testing, and a secondary outcome concerned DPP-4 activity after treatment. This describes the study question and its measurement approach.

The posted results do not report numerical primary or secondary outcome findings. Without the means, standard deviations, group contrasts, or uncertainty estimates, it is not possible to state the direction or size of any difference, or how precisely it was estimated. The registry record also lists no analyses. It therefore does not support a statistical conclusion about the proposed mechanism or about whether response groups differed in the measured biomarkers.

Even if group-specific biomarker differences were reported, the non-randomized design would limit causal interpretation. The groups are described by their response to sitagliptin, and the criteria for that classification are not reported in the registry record. A difference between such groups would not, by itself, show that group status caused a biomarker pattern or that the treatment caused a particular change. The record does not provide an adjustment strategy that would address possible group differences.

The study’s stated purpose includes evaluating appropriate patients for DPP-4 inhibitor treatment. The registered information does not provide the patient-level characteristics, response definition, clinical outcome findings, or analysis needed to evaluate treatment selection. The biomarker endpoint is not a direct report of clinical benefit or harm. The safety record lists zero serious and zero other adverse events in each group, while deaths are not reported in the registry record; these entries alone do not characterize overall safety.

Accordingly, the record is informative about the study’s design and intended biological question, but not about the numerical results or their precision. It should not be read as evidence for or against a treatment effect.

13. Why This Trial Matters Statistically

This study is statistically interesting because it combines repeated biomarker measurements with groups defined by response status. Repeated measurements can reveal patterns over time that a single measurement would not capture. They also require analytical methods that recognize that measurements from the same participant are related. The registry record identifies a series of measurement times but does not report the analysis used to account for that structure.

The non-randomized grouping is also important. Responders and hypo-responders are not described as groups assigned at random to distinct treatments. The contrast is therefore observational, and potential differences between groups complicate interpretation. This is a useful reminder that a comparison can be clinically motivated without having the causal protections of random allocation.

The registered primary measure is a biomarker rather than a clinical outcome. Biomarker studies can address biological questions and help characterize response patterns, but measurement differences do not automatically establish differences in patient-important outcomes. The study’s stated interest in a mechanism should therefore be kept distinct from a conclusion about treatment benefit or treatment selection.

Finally, the record illustrates why design information and results information must be read separately. It gives the primary endpoint definition, measurement schedule, study groups, and safety counts, yet does not report outcome estimates or analyses. A clear description of what was intended does not replace results needed to evaluate magnitude, uncertainty, and robustness. The distinction is central to sound interpretation of clinical research records.

14. 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 main limitation of the registered information is the absence of numerical efficacy results. The registry record does not report active GLP-1 means, standard deviations, group comparisons, confidence intervals, or p-values. It also lists no analyses. The magnitude, direction, and precision of the primary outcome therefore cannot be assessed from the posted results.

The non-randomized design limits causal interpretation of any responder-group contrast. The record does not report how response or hypo-response was defined, how participants entered the groups, or whether analyses adjusted for group differences. It also does not identify a separate untreated or placebo group. These details constrain what can be inferred about treatment effects or the source of any biomarker differences.

The endpoint includes repeated measurements across several time points and before and after treatment, but the statistical approach for these data is not reported in the registry record. The planned primary contrast, handling of within-participant dependence, missing-data methods, and analysis populations are not reported. The record lists five outcome measures but does not state how multiplicity was addressed.

The safety record gives counts but not further information about observation duration, adverse-event ascertainment, event definitions, or relationship to treatment. Deaths are not reported in the registry record. Thus, the safety entries cannot fully characterize risks or establish that no events occurred beyond those recorded.

Finally, the record states enrollment and study dates but does not provide participant flow or confirm how many participants contributed complete data to each efficacy outcome. The listed planning assumptions are not a substitute for an account of the study’s own design justification or observed precision.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pharmacokinetics Study of Dipeptidyl Peptidase 4 Inhibitor to Control Type 2 Diabetes Mellitus — NCT01449747.
• Registry record last updated 2015-12-14; status last verified 2015-11.
• Results first posted 2015-12-14.
• 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.

18. Record Summary

This completed Phase 4 study was non-randomized, unmasked, and parallel-group. It examined sitagliptin hypo-response patients and sitagliptin response patients, with a stated enrollment of 24. The sponsor was The Catholic University of Korea; the record lists a start of 2011-12 and primary completion of 2014-08.

The primary outcome was mean active GLP-1 concentration during meal tolerance testing before and after sitagliptin treatment, with measurements specified at 0, 15, 30, 45, 60, 90, 120, and 180 min. The record lists a secondary DPP-4 activity outcome and five outcome measures overall. It lists no analyses, and numerical outcome results are not reported in the registry record.

The safety record lists zero serious and zero other adverse events in each response group, with 12 participants at risk per group. Deaths are not reported in the registry record. The registered information describes the study question and design but does not provide the estimates needed to assess biomarker differences or their precision.