SNP Study of DPP-4 and GLP-1R in Chinese People (Including Diabetes Patients): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for SNP Study of DPP-4 and GLP-1R in Chinese People (Including Diabetes Patients) (NCT03108521), a non-randomized phase 4 study. The primary outcome is Glycosylated Hemoglobin A1c (HbA1c).

2. Clinical Question

The study title and summary frame two related questions: whether genetic variation is associated with diabetes status, and whether genetic variation is associated with response to an incretin-based treatment. These questions require different comparisons. Comparing gene variants between the sitagliptin group and the non-T2DM group addresses differences by diabetes status, while studying treatment response requires measurements of change among treated participants and an analysis relating that change to genetic variation.

The registry lists HbA1c as the primary outcome, but does not report the group values, changes, uncertainty estimates, or a test of association between genotype and HbA1c response. It therefore does not establish how the primary outcome varied or whether any variation was associated with genetic polymorphisms. The stated primary-outcome description also says that non-T2D subjects were tested only at baseline, while reporting paired HbA1c measurements for 69 of 71 patients who completed the study. The record does not clarify how these statements fit together.

The non-T2DM group should not be read as a randomized or otherwise equivalent control for the sitagliptin group. Its stated role was to contribute genetic information for examining SNP differences between people with and without T2D. The posted record does not support interpreting a comparison between these groups as an estimate of the effect of sitagliptin.

3. Trial Design

This was a phase 4, non-randomized, parallel-group study sponsored by Sichuan Provincial People's Hospital. The registry lists an enrollment of 119 and a completed status. The recorded study start was 2016-04-21, and primary completion was 2018-01-04. Masking was listed as none.

The registry describes a Sitagliptin group and a non-T2DM group. Participants in the Sitagliptin group were to receive sitagliptin phosphate tablets at a recommended dose of 100mg once daily for 3 months. The non-T2DM group was described as T2D-free; its gene information was intended for examining SNP differences between people with and without T2D. These groups therefore had different roles and should not be treated as interchangeable arms of a controlled treatment comparison.

Non-randomized allocation means the registry does not describe assignment by chance. The record does not report how participants entered either group, whether the groups were matched, or what factors were considered when comparing them. Without random allocation and a like-for-like comparator, group differences may reflect characteristics other than the treatment or genetic variation under study. The registry also lists no masking, so it does not describe blinding of participants or study personnel.

The posted record identifies an HbA1c outcome with a 12-week timeframe and lists secondary outcomes for gene polymorphism, change in blood glucose, change in insulin, and change in C-peptide. It does not report numerical results for these outcomes. The specific analysis plan, including how genetic variants and treatment response were to be related, is not reported in the registry record.

The record’s primary-outcome description states that non-T2D subjects were tested for HbA1c only at baseline. It also states that among the 71 patients who completed the study, 69 had HbA1c measurements at both baseline and study endpoint, while 2 did not have HbA1c measured for personal reasons. The registry does not explain the relationship between these statements or identify the analysis population for the primary outcome.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: non-T2D subjects only tested HbA1c at baseline. Of the 71 patients who completed the study, 69 collected HbA1c at both baseline and study endpoint, and 2 subjects did not carry out HbA1c measurement for personal reasons.

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 Glycosylated Hemoglobin A1c (HbA1c), measured over 12 weeks later.

Glycosylated hemoglobin A1c, or HbA1c, is a continuous measure reported in the registry as a percentage. The primary outcome is described as the mean with standard deviation, and its timeframe is 12 weeks later. HbA1c is used in clinical research as a measure related to blood glucose over time, rather than a single blood-glucose reading. In general, a continuous measure can be summarized by its mean to describe its central value and by its standard deviation to describe variation among observations.

The registry record does not report the mean HbA1c values, standard deviations, changes from baseline, or a between-group estimate. It therefore does not show the direction or size of any observed HbA1c change, nor the precision of an estimated change. No confidence interval or statistical test for this endpoint is reported.

The outcome description needs careful reading: it says non-T2D subjects had HbA1c measured only at baseline, and also says that 69 of 71 patients who completed the study had measurements at both baseline and endpoint. The record does not clarify whether these paired measurements refer only to the treated group, how the non-T2DM observations were used, or which participants contributed to the primary analysis. The endpoint is registered, but its numerical results and analysis population are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the outcome summary mean?

The primary outcome is a continuous measure, HbA1c, summarized as a mean and standard deviation. In general, the mean describes the central value of measurements, while the standard deviation describes how spread out individual measurements are around that mean. These are descriptive statistics: they do not, on their own, establish a treatment effect or an association with genetic variation. The registry record does not report the actual HbA1c mean or standard deviation.

When the same outcome is measured at baseline and follow-up, an analysis may focus on the change within each participant. A paired analysis uses the link between measurements from the same person. This can account for the fact that repeated measurements on one person are not independent. However, the registry record does not report a change estimate or specify whether its primary analysis used paired differences, endpoint values, or another approach. Its description of measurements also leaves the analysis population unclear.

Why does the study design affect interpretation?

General statistical context: random allocation can help balance measured and unmeasured participant characteristics between treatment groups, on average. In a non-randomized study, differences in participant characteristics may coincide with differences in treatment or group membership. Such differences can make a group contrast difficult to interpret as a treatment effect. This is especially relevant because the registry describes the non-T2DM group as a genetic comparison group rather than a like-for-like treatment control.

The registry identifies parallel groups and no masking. It does not report the process for allocating participants, any matching strategy, or an adjustment model. It is therefore not possible to determine from the record whether or how measured differences between groups were addressed. A comparison of the Sitagliptin group with the non-T2DM group should not be treated as a randomized comparison.

What would an association analysis need to convey?

The study objective concerns genetic polymorphisms and individual differences in response to sitagliptin. In general, an analysis of this question would need to define the response measure, identify how genetic variants are coded or grouped, and estimate the relationship between genotype and response. It would also need to state which participants and observations were included and how relevant sources of variation were handled. The registry record does not report these analytic details or an association estimate.

Gene-polymorphism comparisons by diabetes status are a separate analytic question. Such comparisons describe whether variant distributions differ between the groups as observed. They do not, by themselves, show that a variant caused diabetes or caused a difference in treatment response. The registry lists types of gene polymorphism as a secondary outcome but does not report the observed distributions or their analysis.

How should uncertainty be understood?

General statistical context: an estimate is more informative when accompanied by a measure of uncertainty. A confidence interval gives a range of values compatible with the data and the method used, under its assumptions. A narrow interval indicates greater precision than a wide interval, although precision is not the same as freedom from bias. A p-value can address evidence against a specified null hypothesis, but it does not give the probability that a hypothesis is true and does not measure the size or importance of an effect. The registry record reports no confidence intervals or p-values for the listed outcomes.

Standard deviations and confidence intervals answer different questions. A standard deviation describes variation among individual observations; a confidence interval describes uncertainty around an estimate, such as a mean or contrast. The record’s primary-outcome description specifies mean and standard deviation, but does not provide their values or an interval for a treatment-response estimate.

What can the adverse-event counts show?

The registry reports serious adverse event counts and counts for other adverse events by group. Counts are descriptive, and their interpretation depends on the participants at risk, the event definitions, and the way events were collected. The record lists zero serious adverse events in each group, but does not provide further detail on event definitions, ascertainment, timing, or severity grading. A zero count in a registry entry does not establish that no event could occur or that groups have equivalent safety profiles.

What analysis details are absent?

The registry lists 5 outcome measures and 0 analyses. It does not report a statistical analysis plan, the model used for the continuous outcome, handling of genetic comparisons, adjustment for potential confounders, or how missing observations were treated. It also does not report whether analyses were planned at interim time points. These details are not reported in the registry record, so the exact inferential methods and assumptions cannot be assessed from the posted information.

General statistical context: model assumptions matter because they determine how estimates and uncertainty are calculated. For continuous outcomes, assumptions may concern the distribution of residuals, the relationship between predictors and outcomes, and the independence of observations. For genetic association analyses, the definition of the variants and the number of comparisons can also affect interpretation. The posted record does not state which assumptions or procedures were used in this study, so no specific method should be attributed to it.

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("Sitagliptin Group")
n   <- c(69)
m   <- c(6.78)
sp  <- c(0.82)
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  Sitagliptin Group  69  6.780  0.820  6.583  6.977

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 5 outcome measures, including the primary HbA1c outcome and secondary outcomes for types of gene polymorphism, change in blood glucose, change in insulin, and change in C-peptide. It reports 0 analyses. The statistical plan for these outcomes, including which comparisons were primary or exploratory and whether any multiplicity adjustment was intended, is not reported in the registry record.

General statistical context: when multiple outcomes, genetic variants, or subgroup comparisons are examined, the chance of finding at least one apparently unusual result can increase if each is assessed separately without accounting for the number of comparisons. Multiplicity procedures can change how evidence is evaluated. The record does not say whether such procedures were used, so the degree to which multiplicity was addressed cannot be determined.

For missing HbA1c data, the registry states that 69 of 71 patients who completed the study had measurements at both baseline and endpoint, while 2 did not undergo HbA1c measurement for personal reasons. It also states that non-T2D subjects had HbA1c tested only at baseline. The record does not explain how these statements relate, identify the analysis population, or say how missing measurements were handled. It does not report whether participants with incomplete measurements were excluded or whether another approach was used.

The registry does not describe missingness for the secondary outcomes or genetic measurements. It also does not report the planned statistical analysis population, any interim analysis, or a sample-size justification. These matters are not reported in the registry record; no assumptions about their handling can be made from the posted results.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports zero serious adverse events among 71 participants at risk in the Sitagliptin group and zero among 36 participants at risk in the non-T2DM group. It reports 12 participants with other adverse events among 71 at risk in the Sitagliptin group, and zero among 36 at risk in the non-T2DM group. Deaths are recorded as zero in both groups.

These counts are descriptive registry entries. The non-T2DM group was not a like-for-like treatment control, so differences in event counts should not be interpreted as a comparative estimate of sitagliptin safety. The record does not report definitions for serious and other adverse events, how events were collected, their timing, or their clinical details. It also does not provide an uncertainty estimate for the counts. The absence of a recorded serious event in these groups does not establish the absence of risk more generally, and the counts alone do not show whether the groups differ in safety.

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

The registry record establishes that a non-randomized phase 4 study was registered to examine genetic polymorphisms related to incretin pathways, diabetes status, and response to sitagliptin. It describes a Sitagliptin group, a non-T2DM genetic comparison group, an HbA1c primary outcome, and secondary outcomes relating to gene polymorphism and metabolic measures. It also records completion of the study.

The posted record does not include numerical results for the primary HbA1c outcome or the listed secondary outcomes. It therefore cannot show how HbA1c changed, how gene variants were distributed, or whether a genetic variant was associated with response. No estimate, confidence interval, or statistical test for these questions is reported. The aims and outcome names should not be mistaken for evidence that a particular association or treatment response was observed.

The design also limits what comparisons can mean. The non-T2DM group was not described as a treatment control, and the registry flags the arms as not being a like-for-like comparison. Consequently, differences between the groups cannot be interpreted as the effect of sitagliptin. The record does not describe adjustment for differences between groups or provide a model that could support a causal interpretation.

General statistical context: an observed association is not necessarily causal, particularly when treatment or group membership is not randomized. Precision and bias are distinct: an estimate can be precise but still affected by systematic differences or limitations in measurement. Since the registry does not report outcome estimates or analytic details, neither precision nor the potential influence of bias can be evaluated for the main questions.

The record’s description of HbA1c measurements is also not fully clear. It says non-T2D subjects were tested only at baseline, while reporting paired baseline and endpoint measurements for 69 of 71 study completers. It does not clarify the relationship between these statements or identify the primary analysis population. The posted information supports a cautious account of the study design and reporting, not a conclusion about treatment benefit, lack of benefit, or a genetic predictor.

14. Why This Trial Matters Statistically

This study is statistically notable for placing two questions alongside each other: whether genetic polymorphism distributions differ by diabetes status, and whether genetic variation is related to individual differences in response to sitagliptin. These are related research aims, but they require distinct comparisons and interpretations. A genetic difference between people with and without T2D is not the same finding as a genotype-associated difference in treatment response.

The registry’s group descriptions make that distinction important. The non-T2DM group was intended to contribute gene information for comparison by diabetes status, rather than to serve as a treatment control. The non-randomized design also means a direct group contrast cannot be treated as a randomized treatment comparison. Clear separation of descriptive genetic comparisons from treatment-response analyses is central to interpreting studies with this structure.

The record also illustrates why an outcome name is not enough to evaluate evidence. HbA1c is identified as the primary endpoint, but its numerical results, uncertainty, and analysis are not reported. The outcome description gives partial information about measurement availability while leaving the analysis population unclear. These reporting gaps prevent assessment of the magnitude, precision, and robustness of any result.

General statistical context: reporting estimates alongside uncertainty and documenting analysis populations helps readers distinguish observed data from conclusions drawn through a model. For genetic questions, describing variant definitions, comparisons, and analysis methods is also necessary to assess how findings were obtained. The registry entry identifies the broad questions but does not provide those results or methods. Its statistical importance lies in clarifying what the study set out to examine while also showing how much the available record leaves unresolved.

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 central limitation for interpretation is that the registry record does not report numerical outcome results or the analyses used to evaluate them. It is therefore not possible to assess the size, direction, precision, or statistical significance of HbA1c changes or genetic associations from the posted information.

The study was non-randomized, had no masking, and used groups with different stated purposes. The non-T2DM group was intended for genetic comparisons by diabetes status, not as a like-for-like treatment control. The record does not describe allocation procedures, matching, adjustment for group differences, or other methods for addressing confounding.

The primary-outcome description is internally difficult to interpret: it says non-T2D subjects were tested for HbA1c only at baseline, and also reports paired measurements for 69 of 71 patients who completed the study. It does not explain which group those paired observations refer to, identify the primary analysis population, or state how missing HbA1c measurements were handled. The reasons for the 2 missing measurements are recorded as personal reasons, but no further detail is given.

The registry lists secondary outcomes but no analyses. It does not report the statistical model, handling of multiple comparisons, genetic variant definitions, analysis plan, sample-size justification, or whether interim analyses were conducted. Definitions and collection procedures for adverse events are also not reported. These omissions limit assessment of both efficacy-related questions and safety counts; they should not be filled in by assumptions.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: SNP Study of DPP-4 and GLP-1R in Chinese People (Including Diabetes Patients) — NCT03108521.
• Registry record last updated 2020-07-30; status last verified 2020-07.
• Results first posted 2020-07-30.
• 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

The registry describes a completed, phase 4, non-randomized, parallel study with no masking. It lists enrollment of 119 and Sichuan Provincial People's Hospital as sponsor. The study aimed to examine incretin-related gene polymorphisms in relation to diabetes status and response to sitagliptin. The intervention description specifies sitagliptin phosphate tablets at 100mg once daily for 3 months; the non-T2DM group was described as T2D-free and used for genetic comparisons.

HbA1c was registered as the primary outcome with a 12-week timeframe. Secondary outcomes included gene polymorphism, blood glucose, insulin, and C-peptide measures. The registry reports limited HbA1c measurement details and adverse-event counts, but no numerical primary or secondary outcome results and no analyses. The primary-outcome population and missing-measurement handling are not clearly described, so treatment-response and genetic-association conclusions cannot be assessed from the registry record.