Assessing the Behavior of Met DR in Subjects With Kidney Dysfunction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessing the Behavior of Met DR in Subjects With Kidney Dysfunction (NCT01658514), a randomized phase 2 study. The primary outcome is AUC (0-t) of Plasma Metformin.

2. Clinical Question

The study is registered as a Phase 2 randomized, double-masked crossover trial. Its stated enrollment is 39. The brief summary describes assessment in participants with normal kidney function and mild, moderate, or severe kidney dysfunction. It also says the study compared Met DR with Met XR and placebo within those levels of kidney function. These details establish the broad clinical and statistical question, but they do not specify which pairwise comparisons were the formal primary contrasts or how the results were intended to guide later research.

The primary outcome is plasma metformin AUC from the time of dosing to the time of the last quantifiable concentration. Its stated timeframe runs from 0 h to 72 hours postdose. AUC is a measure of drug exposure over time, rather than a direct measure of a clinical health outcome. The record does not report a single result comparison across the several outcome categories or time points, so the available description does not support a numerical answer to how exposure differed by treatment or kidney function.

3. Trial Design

The registry describes a randomized, double-masked, crossover study with Phase 2 status and enrollment of 39. It lists three interventions: Met DR, Met XR, and placebo. The Met DR and Met XR arms each involved one dose of 1000 mg; the placebo arm involved one dose of placebo. The trial status is completed. Its recorded start was 2014-01 and its primary completion was 2014-06.

In general, randomization is intended to reduce systematic differences in treatment assignment, while masking is intended to limit the influence of treatment knowledge on study conduct or assessment. A crossover design generally allows treatment comparisons within participants, which can account for some between-person differences. Those are general features of the design, not proof of how the study was implemented. The registry does not report the allocation sequence, the treatment sequence details, the number or duration of treatment periods, or any washout interval. It also does not identify which study roles were masked.

The stated primary analysis population is the PK Evaluable Population. The record does not describe the criteria for belonging to that population, how many participants were included in it, or how it related to the enrolled group. The registry lists renal insufficiency as the condition and describes four kidney-function categories, but it does not report the number of participants in each category.

The study examined pharmacokinetic behavior and safety and tolerability following a single dose. This is distinct from a trial designed to estimate the effects of long-term use or to assess clinical outcomes over an extended treatment period. The registry description does not give details of the clinical protocol beyond the single-dose interventions and the stated assessment timeframe. Sequence generation, concealment of allocation, stopping rules, and the rationale for the enrollment target are not reported in the registry record.

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: PK Evaluable Population

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.

Population: Randomized Population - All subjects were to receive all interventions and are distributed in this module according to their renal function cohort to inform PK analyses comparing these populations

6. Primary Endpoint

The registry lists the primary outcome as AUC (0-t) of Plasma Metformin, measured over from the time of dosing (0 h) to 72 hours postdose.

The primary endpoint is AUC (0-t) of plasma metformin, with units of ng*h/mL. The registry defines it as the area under the concentration-time curve from dosing at 0 h to the time of the last quantifiable concentration following administration. The stated timeframe is from 0 h to 72 hours postdose. The registry reports the endpoint as a least-squares mean with standard error, and identifies the PK Evaluable Population for this outcome.

In general, an area under a concentration-time curve captures drug exposure across a period rather than describing concentration at only one measurement time. It can therefore be useful in pharmacokinetic research examining whether exposure differs across treatments or participant characteristics. The endpoint does not by itself establish a clinical benefit or harm; it is a measure of drug concentration over time.

The registry record does not report the least-squares mean estimates or their standard errors in the registry record for this analysis. It also does not give a single numerical comparison because the primary outcome has several categories or time points and was not reduced to one comparison. Without the relevant estimates and comparisons, the direction and precision of any exposure differences cannot be evaluated from this record summary.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the crossover design mean?

In general, a crossover design evaluates more than one treatment condition within participants, allowing comparisons that may be less affected by stable differences between people. The registry classifies this study as crossover, but does not report the treatment sequences, period structure, washout interval, or the model used to account for within-participant measurements. Those omissions matter because a crossover analysis depends on the relationship among measurements from the same participant and on the design features used to collect them.

What does randomization and masking contribute?

The study is recorded as randomized and double-masked. In general, randomization is used to reduce systematic allocation differences, and masking can reduce the influence of treatment awareness on participant behavior or assessments. The registry does not specify who was masked, how randomization was generated, or how allocation was concealed. The labels alone do not establish that every source of bias was prevented.

How should the least-squares mean be understood?

In general, a least-squares mean is a model-based estimate of a mean, conditional on the structure and terms in the statistical model. It can differ from a simple arithmetic average when a model adjusts for design factors or other variables. The registry reports least-squares means for plasma metformin AUC, but does not identify the model terms, adjustments, or contrast definitions. Therefore, the meaning of any adjusted comparison cannot be reconstructed from the endpoint label alone.

What does the standard error describe?

In general, a standard error describes the sampling uncertainty of an estimate under the analysis model. It is not a measure of the spread of individual participant values. A confidence interval uses an estimate and its uncertainty to express a range of values compatible with the data and assumptions. The record identifies standard error as the dispersion measure, but no numerical estimates or standard errors for the primary outcome are reported in the registry record. The precision of the result therefore cannot be assessed from the available details.

Why does the analysis need to respect the design?

General statistical reasoning calls for analysis methods to reflect how observations were collected. In a crossover study, measurements from the same participant are generally not independent. A method that ignored that dependence could misstate uncertainty. The registry does not report the analysis method, so it is not possible to determine how the posted analysis handled repeated treatment measurements, treatment sequence, period, or other design features. Those are questions for the statistical plan and analysis details, which are not reported in the registry record.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variability exceeds what a statistical model assumes. If the model does not accommodate that extra variability, standard errors can be too small and intervals can appear more precise than warranted. This concept is relevant to many data types, especially counts, but the primary endpoint is continuous AUC. The registry does not report diagnostics or modeling choices that would show whether over-dispersion was considered for any outcome. It would not be justified to claim that over-dispersion occurred in this study.

What can the planning illustrations say?

In general, a sample-size calculation uses assumptions about the target effect, variability, significance level, allocation, and analysis method to illustrate how many participants might be needed for a specified power. The stated planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration is based on a fraction of the observed effect. These are planning assumptions, not observed power and not evidence that the trial was designed using those assumptions. The registry does not report the trial's own sample-size justification or design assumptions. Any sample-size illustrations should be read as conditional planning scenarios rather than a retrospective measure of whether the trial succeeded statistically.

Why are the observed estimates essential?

A design description and endpoint definition cannot substitute for outcome estimates. For a continuous endpoint, interpretation ordinarily requires the estimated means or contrasts, uncertainty measures, and information on the analysis population. In this record, the outcome comprises several categories or time points and has not been reduced to one comparison. The primary estimates and corresponding uncertainty are not reported in the registry record. As a result, no numerical effect size or precision statement can be made from the available information.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures and 10 analyses. The primary outcome is identified as AUC (0-t) of plasma metformin, but it has several categories or time points and is not reduced to one comparison in the available record. The specific comparisons, outcome hierarchy, and any prespecified approach to multiple testing are not reported in the registry record. Consequently, it is not possible to determine whether a multiplicity adjustment was planned or used, or how any adjustment would affect interpretation.

The planning assumptions include a two-sided significance level of 0.05, but those assumptions describe planning illustrations. They do not establish the significance threshold used for the trial's formal analyses. The statistical analysis plan, including any interim analyses or rules for selecting comparisons, is not reported in the registry record. No interim analysis should be inferred from the listed analyses.

The primary outcome identifies the PK Evaluable Population, but its inclusion and exclusion criteria and size are not reported. The registry does not explain how missing pharmacokinetic measurements or participants with incomplete data were handled, whether any imputation was used, or whether analysis populations other than the PK Evaluable Population were examined. The number enrolled is 39, but that does not establish how many contributed to each endpoint or treatment comparison.

Missing-data methods and analysis-population definitions can affect both the estimate and its uncertainty. In general, complete-case analyses, imputation, and model-based approaches rely on different assumptions. Without the study's methods and participant accounting, the robustness of the results to missing data cannot be assessed. These details are not reported in the registry record.

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.

Most frequent non-serious adverse event terms

The registry separates serious adverse events from other adverse events. It records no serious adverse events among the participants at risk in the listed groups: placebo, 0 of 36; Met DR, 0 of 38; and Met XR, 0 of 37. For other adverse events, the registry records 4 of 36 participants for placebo, 12 of 38 for Met DR, and 11 of 37 for Met XR. These are counts of participants affected, not event rates recalculated for comparison.

In general, zero recorded serious events in a group does not prove that the underlying risk is zero. Safety counts are most informative when read with the number of participants assessed, event definitions, follow-up, and the completeness of reporting. The registry does not report the death counts; they should not be interpreted as zero. It also does not provide event-level descriptions, timing, severity, treatment relatedness, or an analysis of differences between groups.

The counts for other adverse events are descriptive. They do not establish that treatment caused an event or that groups differ statistically. No comparative safety estimate or uncertainty measure is reported in the registry record. The recorded figures therefore describe what was entered for the listed groups, while leaving important context for interpretation unavailable.

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

The study addresses how a single dose of delayed-release metformin behaves across kidney-function categories and compares it with extended-release metformin and placebo. Its primary measure, plasma AUC (0-t), represents exposure from dosing until the last quantifiable concentration within the stated 0 h to 72 hours postdose timeframe. This makes the endpoint relevant to a pharmacokinetic question, but it is not itself a clinical outcome or a measure of long-term treatment effects.

The registry record does not provide a single primary comparison or numerical estimates that would show the size, direction, or precision of differences. It therefore does not support a conclusion about whether exposure differed by treatment or kidney-function group. A completed trial status does not fill that gap. No finding about efficacy or clinical benefit can be drawn from the endpoint definition alone.

The listed adverse-event counts give a limited descriptive account: no serious adverse events are recorded among the participants at risk in the three groups, while other adverse events are recorded for some participants. These counts do not establish causation, comparative risk, or the absence of unrecorded events. Death counts are not reported in the registry record.

In general, a statistically interpretable treatment comparison requires an estimate, a measure of uncertainty, and enough information about the analysis to understand the assumptions. For this study, those elements are not available for a single primary contrast. The record can be used to understand the design and the intended pharmacokinetic assessment, but not to quantify or judge the comparative findings. It also cannot establish how results would apply beyond the participants and single-dose setting described.

13. Why This Trial Matters Statistically

This trial is statistically notable because it combines a randomized crossover design with a pharmacokinetic outcome measured over time and across kidney-function categories. In general, a crossover structure can make within-participant comparisons informative by accounting for stable differences between people. At the same time, it requires analysis that reflects repeated measurements and treatment sequence. The registry identifies the design but does not report the analysis details needed to evaluate that alignment.

The least-squares mean and standard error labels indicate a model-based continuous-outcome summary. Such summaries can be useful when the model matches the design and the estimand is clearly specified. Here, the model terms and formal contrasts are not reported. The primary outcome also spans several categories or time points and is not reduced to one comparison, limiting direct interpretation of the posted record.

The study also illustrates why endpoint definition, analysis population, and numerical results must be read together. AUC has a clear pharmacokinetic interpretation, and the PK Evaluable Population is named, but the record does not provide the population criteria, endpoint estimates, or precision measures. Without those details, the research question is identifiable while its statistical answer remains unresolved in the registry record.

Finally, the safety counts show why descriptive data need context. Group counts alone do not establish causal differences, and the death counts are not reported. The case emphasizes that a completed randomized study can still have limits as a source of statistical interpretation when comparisons, uncertainty, and analysis procedures are not reported.

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 for interpreting the primary endpoint is that the registry outcome has several categories or time points and is not reduced to one comparison. Numerical least-squares means, standard errors, treatment contrasts, confidence intervals, and p-values are not reported in the registry record. The direction, magnitude, and precision of the pharmacokinetic findings therefore cannot be assessed.

The analysis population is named as the PK Evaluable Population, but the criteria and its size are not reported. The registry does not give participant counts by kidney-function category or explain how missing or unusable pharmacokinetic data were handled. Enrollment of 39 does not establish the number analyzed for each outcome or comparison.

Although the study is described as randomized, double-masked, and crossover, the sequence and period details, washout interval, masking roles, and statistical model are not reported. The registry also does not provide the protocol or statistical analysis plan, sample-size justification, or multiplicity approach. It is consequently not possible to evaluate the analysis assumptions or determine how the crossover structure was reflected in estimation.

The safety information is limited to group counts for serious and other adverse events. Death counts are not reported, and event details, timing, severity, relatedness, and comparative uncertainty are unavailable. The single-dose design and stated pharmacokinetic timeframe also limit what the study description can establish about outcomes beyond the measured exposure period. These limitations concern the available registry record and do not, by themselves, establish flaws in the conduct of the trial.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Assessing the Behavior of Met DR in Subjects With Kidney Dysfunction — NCT01658514.
• Registry record last updated 2015-12-30; status last verified 2015-11.
• Results first posted 2015-12-30.
• 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.

18. Record Summary

NCT01658514 is a completed Phase 2 randomized, double-masked crossover study of single-dose delayed-release metformin in participants described as having normal kidney function or mild, moderate, or severe kidney dysfunction. The listed interventions were Met DR, Met XR, and placebo; the two metformin interventions were single doses of 1000 mg. Enrollment was 39.

The primary endpoint was plasma metformin AUC (0-t), measured from dosing to the last quantifiable concentration, with a stated timeframe of 0 h to 72 hours postdose. The registry identifies least-squares mean and standard error reporting and names the PK Evaluable Population. It does not reduce the outcome to one comparison or report numerical primary estimates in the record details used for this interpretation.

The safety record lists no serious adverse events among participants at risk in the three groups, and lists other adverse events affecting participants in each group. Death counts are not reported. Analysis methods, missing-data handling, and multiplicity procedures are not reported in the registry record.