Preservation of Pancreatic Beta Cell Function Through Insulin Pump Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Preservation of Pancreatic Beta Cell Function Through Insulin Pump Therapy (NCT00574405), a randomized na study. The primary outcome is Change in Mixed-meal-stimulated Peak C-peptide Value (Via Mixed-meal Tolerance Test) After 12 Months of Insulin Pump Therapy, Compared With MDI..

2. Clinical Question

The study’s stated aim was to test whether starting pump therapy at diagnosis could preserve or enhance residual pancreatic beta-cell secretory capacity. The primary endpoint was framed as a change in peak C-peptide measured by a mixed-meal tolerance test. Glycemic control, daily insulin requirements, adverse glycemic consequences, and satisfaction and compliance were also listed as secondary outcomes.

The clinical question is comparative, but the posted primary results do not include an estimable between-group comparison. The registry lists per-protocol group means and standard deviations, while its stated reason for not producing a two-arm continuous-endpoint comparison is that values were missing or not estimable for that purpose. The results therefore describe the posted groups, rather than providing a complete estimate of the difference between treatment strategies.

3. Trial Design

This was a completed, randomized, parallel-group trial with no masking. The registry lists enrollment of 24 participants. The study began in 2005-04, and primary completion was recorded as 2010-03. The sponsor was Arkansas Children's Hospital Research Institute. The phase is listed as NA.

The two treatment strategies were multiple daily injections and continuous subcutaneous insulin infusion. The injection regimen was described as 3-4+ injections per day using either split-mix NPH insulin plus regular insulin or Lantus plus Novolog® or Humalog®. The pump arm used an Animas Corporation insulin pump, model IR 1200, and was described as starting at diagnosis. The record identifies randomization but does not report the sequence-generation method, allocation concealment, or the allocation ratio.

The primary outcome population is identified as per protocol. The posted primary outcome counts are 9 for multiple daily injections and 10 for pump therapy. These are the counts attached to the reported outcome values; the registry does not explain why they differ from the total enrollment. Safety summaries list 12 participants at risk in each group. Those denominators serve a different purpose and should not be treated as the primary endpoint sample sizes.

The registry record does not report a detailed protocol, planned follow-up procedures beyond the stated outcome timeframes, or a full statistical analysis plan. It also does not report how participants were assigned to the per-protocol population. The randomized design supports a comparative question in principle, but the information posted does not establish how the analysis handled departures from assigned treatment or missing measurements.

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.

Before assignment: One subject in each group withdrew from further participation after initial randomization, possibly because of dissatisfaction with the assigned mode of treatment.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Per protocol

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 Change in Mixed-meal-stimulated Peak C-peptide Value (Via Mixed-meal Tolerance Test) After 12 Months of Insulin Pump Therapy, Compared With MDI., measured over 12 months.

The primary endpoint is described as the change in mixed-meal-stimulated peak C-peptide value, measured by a mixed-meal tolerance test after 12 months of insulin pump therapy compared with multiple daily injections. C-peptide is released when the body produces its own insulin, so its concentration is used as an indicator of residual endogenous insulin secretion. A mixed meal provides a stimulus for secretion, allowing the response to be assessed under a defined test condition. These are general features of the measure.

The registry specifies a mean as the summary measure, a standard deviation as the measure of spread, and ng/mL as the unit. Its primary-outcome population is per protocol. The posted arm values are 1.8 ng/mL with a standard deviation of 1.4 for multiple daily injections, based on 9 participants, and 3.1 ng/mL with a standard deviation of 2.2 for pump therapy, based on 10 participants.

Although the endpoint wording refers to change, baseline values and a separate change estimate are not reported in the registry record. The record also does not provide an estimable treatment-group contrast, confidence interval, or test result. The listed group summaries therefore do not by themselves establish the size or precision of a difference in change between the strategies.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What do the group summaries describe?

The primary outcome uses a mean and standard deviation, appropriate descriptive quantities for a continuous measurement such as C-peptide concentration. The mean gives the average for the participants included in each group summary. The standard deviation describes variability among their measurements. Neither quantity alone is a direct estimate of the uncertainty around the difference between groups.

The registry reports the mean and standard deviation for each arm, together with the number of participants contributing to those summaries. The means are 1.8 ng/mL for multiple daily injections and 3.1 ng/mL for pump therapy; the standard deviations are 1.4 and 2.2, respectively. The associated counts are 9 and 10. These values are useful for describing the observed groups, but they do not supply a standard error, confidence interval, or formal comparison.

Why does the comparison matter?

The clinical question concerns whether the outcome differs between randomized treatment strategies, rather than whether either group has a particular mean in isolation. A treatment contrast is an estimate of the difference between groups under a defined analysis. A confidence interval gives a range of values compatible with the data and analysis assumptions, and helps communicate the precision of that estimate. A hypothesis test addresses compatibility with a specified null hypothesis, but a p-value does not measure the size or clinical importance of an effect.

For this endpoint, the registry does not report an estimable two-arm comparison. It states that values were missing or not estimable for a two-arm comparison of a continuous endpoint. No confidence interval or test result for the primary comparison is posted. It would therefore be inappropriate to derive a contrast or its uncertainty from the arm summaries here, particularly because the record does not clarify the exact status of the values as changes or endpoint measurements.

What does randomization contribute?

Randomization is a design method intended to make treatment groups comparable, on average, with respect to factors known and unknown at the time of assignment. It does not guarantee that groups will be identical, especially in a small trial, and it does not address missing outcome data by itself. A non-masked design means that masking is listed as none; the registry does not describe any additional steps to reduce the influence of treatment knowledge on outcome assessment or analysis.

The parallel model means the study compared separate groups assigned to different strategies. The registry identifies the trial as randomized but does not report the randomization procedure or allocation concealment. Those details are relevant to judging how assignment was implemented, but are not reported in the registry record.

How should the per-protocol results be read?

The primary outcome population is specified as per protocol. In general, a per-protocol analysis summarizes participants who meet the study’s criteria for following the assigned treatment and protocol. The precise criteria can vary and need to be stated to assess who is included and how exclusions may affect a comparison. Those criteria and the method for assigning participants to this population are not reported in the registry record.

The registry lists 24 enrolled participants, but the primary endpoint values are based on 9 participants in the injection group and 10 in the pump group. The record does not give a participant flow or explain this difference. The safety summaries use 12 participants at risk in each group, so their denominators should not be substituted for the primary endpoint counts. Different outcomes can have different available data, but the reasons for the counts in this trial are not reported.

What can planning calculations tell readers?

The registry describes a sample-size planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It defines the effect to detect as a stated fraction of the observed effect. Such calculations are planning illustrations: they do not say how many participants were actually analyzed, and they are not observed power. The record does not report a sample-size justification for the trial’s original design. Any planning values should be interpreted in light of the assumptions and the uncertainty in the observed effect; the primary comparison itself is not estimable in the posted results.

Why does spread and missingness matter?

Participant measurements vary, as reflected by the standard deviations. Greater variability generally makes it harder to estimate a group mean or a difference precisely when other factors are unchanged. Missing outcome data also matter because the analyzed participants may differ from those without measurements. The registry does not report the amount, reasons, or handling of missing primary endpoint data, so their potential influence cannot be evaluated from the posted record.

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("Multiple Daily Injection Therapy", "Insulin Pump Therapy, Started at Diagnosis.")
n   <- c(9, 10)
m   <- c(1.8, 3.1)
sp  <- c(1.4, 2.2)
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  Multiple Daily Injection Therapy  9  1.800  1.400  0.724  2.876
CARM  Insulin Pump Therapy, Started at Diagnosis.  10  3.100  2.200  1.526  4.674

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four secondary outcomes in addition to the primary outcome: changes in hemoglobin A1c and daily blood glucose measurements, changes in daily insulin requirements, frequency of adverse glycemic consequences, and patient satisfaction and compliance. It reports five outcome measures in total and no analyses. The record does not report a multiplicity strategy, such as whether secondary outcomes were treated as exploratory or whether any adjustment for multiple testing was planned.

When several outcomes are tested, the chance of at least one apparently notable result can increase if each is interpreted separately. This is a general statistical consideration, not a finding about this trial. Because no secondary analyses are listed, the registry record does not support conclusions about those outcomes or about how any potential multiplicity was handled.

The primary endpoint population is described as per protocol. The record does not report the criteria for that population, a missing-data method, imputation, or sensitivity analyses. It also does not explain why the primary summaries include 9 and 10 participants when enrollment was 24. The difference cannot be attributed to any particular cause on the basis of the registry record.

Safety summaries report 12 participants at risk in each group, but this does not resolve missingness in the primary endpoint. The record does not describe whether all randomized participants were included in any intention-to-treat analysis. Thus, the analysis population and the handling of incomplete measurements remain important uncertainties when interpreting the posted results.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hospitilized for treatment of urinary tract infection (8.3%).

The safety record lists 12 participants at risk in each group. It reports serious adverse events affecting 0 participants in the multiple daily injection group and 1 participant in the pump group. The listed top serious event term is “Hospitilized for treatment of Urinary tract infection,” with 8.3% recorded. The registry does not provide further detail about the event in this summary.

Other adverse events are listed as affecting 10 of 12 participants in the injection group and 7 of 12 in the pump group. These counts are separate from the serious adverse event counts. The record does not describe whether events were judged related to treatment, how events were collected, or their severity beyond the serious-versus-other classification.

These are descriptive safety counts, not a comparative statistical analysis. The groups are small, and no confidence interval or test for a safety difference is reported. The deaths field is not reported in the registry record. The counts should not be interpreted as establishing that either strategy caused or prevented an event, and they do not address the primary C-peptide outcome.

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

The posted results give descriptive per-protocol summaries for the primary C-peptide endpoint and counts for adverse events. The pump group’s listed mean is 3.1 ng/mL, compared with 1.8 ng/mL for the multiple daily injection group. The registry does not provide an estimable two-arm comparison, a confidence interval, or a p-value. The summaries therefore cannot establish how precisely the groups differ or whether a difference in the stated change endpoint is supported by an analysis.

The endpoint wording concerns change after 12 months, but baseline values and separate change estimates are not reported in the registry record. The number of participants in the primary outcome summaries is also smaller than total enrollment, and the record does not explain why. These gaps prevent a clear assessment of the full randomized group experience or the effect of missing measurements on the result.

The design was randomized and parallel, which is relevant to a comparative question, but design alone does not supply a treatment-effect estimate. The posted record does not describe the allocation procedure, detailed analysis plan, or handling of missing data. The primary population is per protocol, and the criteria for that population are not reported.

These results should not be read as showing that either treatment strategy does or does not preserve beta-cell function. They describe the values and safety counts that the registry reports, with substantial limits on comparative interpretation. The listed secondary outcomes are not accompanied by analyses, so the registry record does not establish results for glycemic control, insulin requirements, adverse glycemic consequences, satisfaction, or compliance.

14. Why This Trial Matters Statistically

This trial is statistically relevant because it asks a comparative question using random assignment, a continuous biological endpoint, and a per-protocol analysis population. The registry provides group means and standard deviations, which describe the observed measurements, but does not provide an estimable comparison for the primary outcome. That distinction illustrates why descriptive arm summaries and an effect estimate answer different questions.

The counts also make the analysis population important. Enrollment is listed as 24, while the primary endpoint summaries use 9 participants in the injection arm and 10 in the pump arm. Safety denominators are 12 per group. The record does not explain these differences, so readers cannot determine how outcome availability, protocol adherence, or other factors shaped the analysis.

The study also lists several secondary outcomes, but no analyses are posted for them. When multiple outcomes are planned, transparent reporting of which were analyzed and how results were interpreted helps readers distinguish the primary question from exploratory questions. The registry does not report such details, including any multiplicity approach.

Finally, the record describes a planning illustration based on an observed effect but does not report the trial’s own sample-size justification. Planning calculations can help frame future study design, but they do not replace an adequately reported treatment estimate or demonstrate that a completed trial had sufficient precision. The central statistical lesson is that a randomized design, group summaries, and a clinical hypothesis do not by themselves establish a comparative result when the primary contrast is not estimable.

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 primary comparison cannot be interpreted as a quantified treatment effect because the registry marks it as not estimable for the continuous endpoint. No contrast, confidence interval, or p-value is reported. The arm summaries are provided, but the registry does not clarify whether those values represent endpoint measurements, changes, or another calculation beyond the endpoint wording.

The outcome counts are limited relative to the listed enrollment of 24. Primary summaries are based on 9 participants in the multiple daily injection group and 10 in the pump group, while safety summaries list 12 at risk per group. The registry does not provide participant flow, reasons for unavailable outcomes, or the method used to determine the per-protocol population. Missing-data handling and sensitivity analyses are not reported.

The registry identifies randomization and no masking, but does not report the sequence-generation method, allocation concealment, or allocation ratio. It does not provide a detailed protocol or statistical analysis plan, including criteria for the per-protocol analysis. These omissions limit assessment of the design and analysis decisions.

Four secondary outcomes are listed, but the record lists no analyses. A multiplicity strategy is not reported. Safety counts are descriptive and are not accompanied by comparative uncertainty estimates or details of event relatedness. The deaths field is not reported in the registry record. These limitations restrict conclusions to a description of the posted results rather than a comprehensive assessment of efficacy or safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Preservation of Pancreatic Beta Cell Function Through Insulin Pump Therapy — NCT00574405.
• Registry record last updated 2017-09-13; status last verified 2017-09.
• Results first posted 2011-08-09.
• 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 randomized, non-masked, parallel-group trial with enrollment of 24. It compared multiple daily injection therapy with insulin pump therapy started at diagnosis. The primary outcome was described as change in mixed-meal-stimulated peak C-peptide after 12 months, with the primary population identified as per protocol.

The posted primary summaries are 1.8 ng/mL with a standard deviation of 1.4 for multiple daily injections, based on 9 participants, and 3.1 ng/mL with a standard deviation of 2.2 for pump therapy, based on 10 participants. The registry states that a two-arm comparison was not estimable. Four secondary outcomes are listed, with no analyses reported. Safety summaries list 12 participants at risk per group, serious adverse events affecting 0 and 1 participants, and other adverse events affecting 10 and 7 participants, respectively.

The record does not report a comparative estimate or its precision, explain the primary outcome counts, or describe missing-data handling. The findings are therefore descriptive and do not establish a comparative treatment effect.