Glucose Counterregulation in Long Standing Type 1 Diabetes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Glucose Counterregulation in Long Standing Type 1 Diabetes (NCT01474889), a na na study. The primary outcome is Endogenous Glucose Production.

2. Clinical Question

This is a question about a physiological response under experimentally induced hypoglycemia, rather than a direct comparison of clinical events between randomized treatment groups. The registry describes metabolic testing and symptom generation during insulin-induced hypoglycemia, but does not provide the test results, estimates of change, or statistical uncertainty. It therefore records the research question and outcome definition without allowing readers to determine the size or precision of any observed response. The stated purpose should not be mistaken for evidence that the intervention did or did not produce a particular effect.

3. Trial Design

The study is titled Glucose Counterregulation in Long Standing Type 1 Diabetes, with the official title Effect of Real-Time Continuous Glucose Monitoring on Glucose Counterregulation in Long Standing Type 1 Diabetes. The sponsor is the University of Pennsylvania. The registry lists the study as completed, with a start of 2011-10 and primary completion of 2016-05. Enrollment is recorded as 37.

The registry classifies the model as single group and allocation as NA, with no masking. It lists an RT-CGM device intervention for participants with type 1 diabetes and hypoglycemia unawareness. The arm description says that these participants wore RT-CGM for 18 months. Two additional groups are described as controls: people with type 1 diabetes and people without diabetes. The registry explains that neither group wore a CGM and neither was analyzed at the six-month and 18-month time points. It also says that the outcome measures were not assigned to those control groups because they were used as baseline references for clinical significance.

These details matter when interpreting comparisons. The design is not described as a randomized, like-for-like treatment comparison. The presence of groups labelled as controls does not establish that they received the same procedures or follow-up as the intervention group. The registry does not report the allocation process, eligibility criteria in detail, recruitment methods, participant flow, or a protocol-level explanation of the group structure. The study phase is listed as NA.

The registry’s brief summary says enrollment is complete and describes the study’s aim as determining whether RT-CGM can reverse defective glucose counterregulation and hypoglycemia unawareness in long-standing type 1 diabetes. That is the stated objective, not a result. The numerical primary outcome findings and analysis results 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.

Before assignment: The Intervention Group (Group 1) consists of participants with Type 1 Diabetes complicated by Hypoglycemia Unawareness. There were two Control Groups: (Group 2) T1Ds With Intact Awareness and (Group 3) Non-diabetics are used as a baseline for clinical significance. Neither of these two Control Groups wore a CGM nor were they analyzed at 6-month and 18-month time-points.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Type 1 Diabetes with Hypoglycemia Unawareness. Patients wear an RT-CGM for 18 months.

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: Hypoglycemia Unaware T1 Diabetics are the intervention group. The 2 control groups (Non-diabetics \& T1Ds with intact Awareness) were used for clinical significance and were not assessed for outcome measures. These control group numbers have been included in the participant Flow, Baseline Characteristics and Adverse Events modules only.

6. Primary Endpoint

The registry lists the primary outcome as Endogenous Glucose Production, measured over 6 months.

The primary endpoint is endogenous glucose production, measured in mg/kg/min. The registry describes it as a measure of hepatic glucose output during the final hour of a hypoglycemic clamp, with a six-month timeframe. In physiological terms, endogenous glucose production reflects glucose released from within the body rather than delivered from an external source. Measuring it during induced hypoglycemia provides an indicator of one component of the body’s counterregulatory response.

A continuous measurement can show the magnitude of a physiological response on a scale, rather than simply classifying a participant as having or not having an event. The registry specifies that the reported parameter is a mean and that dispersion is expressed as a standard error. In general, a mean describes the average measurement in a group, while a standard error describes uncertainty in estimating that mean; it is not a description of the spread among individual participants.

The endpoint is relevant to the stated question because the study concerns glucose counterregulation in people with hypoglycemia unawareness. However, the endpoint is only one physiological measure and does not, by itself, summarize every aspect of counterregulation, symptoms, or clinical experience. The registry does not report the observed mean, standard error, change over time, or a comparison estimate for the primary endpoint. Its numerical result and precision are therefore not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry provides some design and outcome definitions but does not report the statistical analysis results. The explanations below describe general statistical concepts and clarify what can and cannot be inferred from the record.

What does a mean describe?

The primary outcome is a continuous measure, endogenous glucose production in mg/kg/min, and the listed parameter is a mean. In general, a mean is a way to describe the central value of measurements in a group. It can be useful for comparing average physiological responses across time or groups, but it does not show how individual measurements are distributed. Participants may have values near the mean or values spread widely around it. The registry does not report the endpoint mean, so no numerical average can be interpreted.

What does a standard error describe?

The registry specifies standard error as the dispersion measure for the primary outcome. In general, a standard error describes the statistical uncertainty in an estimated mean. It is different from a standard deviation, which describes variability among individual measurements. A smaller standard error generally indicates a more precise estimate of a mean, but its interpretation depends on the underlying data and analysis. Since no standard error value is reported for the primary outcome, the precision of the endpoint estimate cannot be assessed.

What would a confidence interval add?

In general, a confidence interval presents a range of values compatible with an estimate under a specified statistical method. It helps readers judge both the range of plausible effects and the precision of the estimate. A narrow interval indicates more precision than a wide interval, while an interval that includes values on different sides of a relevant reference point may leave the direction or importance of an effect uncertain. No confidence interval for the primary endpoint is reported in the registry record. Without an estimate and interval, readers cannot assess whether the evidence is precise or whether it is compatible with a range of possible effects.

Why does the design affect interpretation?

The registry describes the model as single group and allocation as NA, and notes that the control groups were baseline references rather than groups followed at the intervention time points. In general, a randomized concurrent comparison can help separate treatment effects from changes over time and differences between groups, because allocation is intended to balance prognostic factors. A baseline reference does not offer the same protection. Groups can differ for reasons other than the intervention, and measurements made at different times may be affected by changes unrelated to treatment. The record does not describe a randomized treatment-versus-control analysis.

This distinction is especially relevant when a study includes a group that receives an intervention and other groups that serve as reference points. The presence of control labels alone does not establish concurrent follow-up, equal treatment conditions, or random allocation. Here, the record explicitly says neither control group wore a CGM or was analyzed at the six-month and 18-month time points. It also says the control groups were used as a baseline for clinical significance. Any interpretation should retain that stated role rather than treating those groups as equivalent randomized comparators.

How should the endpoint timeframe be read?

The primary outcome is assigned a six-month timeframe, while the intervention arm description says participants wore RT-CGM for 18 months. The record does not provide outcome values or explain all assessment visits. In general, a timeframe identifies when an outcome is intended to be assessed, but it does not on its own reveal how many measurements were collected, which measurements were used in an analysis, or how missing assessments were handled. Those details are not reported in the registry record.

What do the analysis fields establish?

The registry records zero analyses. This means that analysis results are not listed in the record; it does not establish that investigators conducted no statistical analyses. The registry does not report the statistical model, covariates, handling of repeated measurements, assumptions, treatment of outliers, or a plan for sensitivity analyses. It also does not report a protocol-level statistical analysis plan. Those features should not be inferred from the endpoint definition or study objective.

The registry lists four outcome measures. It identifies endogenous glucose production as primary and names secondary outcomes concerning endogenous glucose production and autonomic symptom response to hypoglycemia. The autonomic symptom response label is repeated in the list. The record does not explain whether outcomes were tested separately, combined, or analyzed according to a hierarchy. A statistical hierarchy or multiplicity adjustment therefore cannot be assumed.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variability is greater than a statistical model assumes. It can make standard errors too small and confidence intervals too narrow if the model fails to account for that variability. Its relevance depends on the type of outcome and model. The primary measure is continuous, and no outcome distribution, model, or diagnostics are reported. It is therefore not possible to determine whether over-dispersion was relevant or how variability was handled in the study’s analysis. This general concept should not be mistaken for a claim that over-dispersion occurred in this study.

How should planning calculations be read?

The record describes a sample-size planning illustration using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Such calculations are generally conditional on their assumptions and are intended to illustrate planning requirements. They do not describe the number of participants who experienced an outcome, and they are not observed power. The record’s assumptions do not replace a reported design justification or analysis plan; those are not reported in the registry record. Numerical planning estimates are not reported in the registry record.

Because no numerical primary result or analysis is reported, no recalculation from posted endpoint summary statistics is possible. The registry record does not report summary statistics for such a calculation. Consequently, there is no recalculated estimate to compare with a sponsor analysis, and no discrepancy between such estimates can be assessed from this record. The central statistical conclusion is that the record describes what was intended to be measured but does not provide the results needed to estimate the effect or its uncertainty.

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("Hypoglycemia Unaware T1 Diabetes RT-CGM")
n   <- c(13)
m   <- c(0.54)
sp  <- c(0.07)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Hypoglycemia Unaware T1 Diabetes RT-CGM  13  0.540  0.252  0.387  0.693

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and names endogenous glucose production as the primary outcome. Its secondary outcomes include endogenous glucose production and autonomic symptom response to hypoglycemia; the symptom-response label appears twice. The record does not state how many statistical hypotheses were tested, whether outcomes were tested separately, or whether a testing hierarchy or multiplicity adjustment was used. A statistical plan addressing multiple comparisons is not reported in the registry record.

Multiplicity matters in general when several outcomes or analyses are examined, because the chance of at least one apparently unusual result can increase as the number of tests grows. Whether an adjustment is appropriate depends on the prespecified aims and analysis strategy. Since the registry does not report those details or any analysis results, it is not possible to determine how multiplicity was handled or what it means for any finding.

The record does not describe missing-data methods, reasons for missing measurements, participant flow through follow-up, or an analysis population such as intention-to-treat or per-protocol. Those details are not reported in the registry record. In general, missing observations can affect estimates if the availability of measurements is related to participant characteristics or outcomes. Without information on completeness and handling, readers cannot assess that possibility for this study.

The registry records zero analyses, so no analysis population or missing-data approach is available to interpret from its posted results. This does not prove that analyses were not performed elsewhere; it identifies a limit of the registry record. It also means that readers cannot assess whether all enrolled participants contributed to the primary endpoint or whether exclusions occurred.

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.

The adverse-event record lists three groups: hypoglycemia-unaware participants with type 1 diabetes, a control group with type 1 diabetes, and a control group without diabetes. For serious adverse events, the listed numbers at risk are 13, 12, and 12, respectively, and the number affected is 0 in each group. The record also lists 0 deaths in each group. For other adverse events, the numbers at risk are 13, 12, and 12, respectively, and the number affected is 0 in each group.

These are the registry’s reported counts for the groups and categories shown. They do not establish that no adverse events occurred outside the reporting period, were unrecorded, or were omitted from the registry. The record does not provide event narratives, severity details beyond the serious-event category, exposure-adjusted rates, or a fuller account of safety monitoring. The top serious-event terms list is empty.

Zero reported affected participants should be read as a count in the registry record, not as proof that an intervention is free of risk. The record also does not describe a randomized safety comparison. The listed groups have different roles in the study, so the counts should not be interpreted as a like-for-like estimate of relative safety.

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

This record establishes that the study was designed to investigate glucose counterregulation and hypoglycemia unawareness in long-standing type 1 diabetes in relation to real-time continuous glucose monitoring. It identifies a primary physiological endpoint, endogenous glucose production during the final hour of a hypoglycemic clamp, and gives its unit and stated timeframe. It also documents an intervention arm whose participants wore RT-CGM for 18 months and two control groups used as baseline references.

It does not establish the magnitude or direction of a change in endogenous glucose production. Numerical primary-outcome results, uncertainty estimates, and analysis results are not reported in the registry record. It is therefore not possible to say from the posted results whether the average response changed, how precise an estimate would be, or whether observed data were compatible with a range of effects. The absence of reported results is not evidence that there was no effect, and it is not evidence that there was an effect.

The record also does not show a randomized comparison with concurrent follow-up. The control groups were not assessed at the six-month and 18-month time points, according to the registry. They should therefore be understood as baseline references as described, not automatically as equivalent treatment comparators. This design information limits causal interpretation of any contrast that might appear elsewhere.

The listed safety counts show zero participants affected by reported serious adverse events and zero deaths in each of the three groups, as well as zero affected by other adverse events in each group. These counts describe what is recorded, but do not establish complete ascertainment or prove the absence of risk. They also do not substitute for the missing primary efficacy results.

In practical statistical terms, the registry record communicates the study’s aims, general structure, and outcome definitions more fully than its findings. It supports a description of what investigators intended to examine, but not a conclusion about the observed treatment effect or its clinical importance.

14. Why This Trial Matters Statistically

The study raises a statistically interesting question because its primary endpoint is a physiological measure tied to the proposed mechanism of glucose counterregulation. A continuous measure of endogenous glucose production during induced hypoglycemia can characterize a response that may not be captured by a simple event count. The registry identifies the measurement context, unit, and timing, which helps define what the investigators intended to study.

The record also illustrates why design labels and group roles matter. It lists control groups, but explains that they served as baseline references and were not analyzed at the six-month and 18-month time points. The study is classified as single group, with allocation listed as NA. A reader should not infer a randomized comparison merely from the existence of control groups. Correctly distinguishing reference groups from concurrent comparators is essential to avoid overstating what a contrast can establish.

Another statistical lesson is the distinction between an outcome definition and an outcome result. A clearly named endpoint does not tell readers what value was observed, how much it changed, or how uncertain that estimate is. Here the registry records the primary endpoint and its mean-and-standard-error format, but no numerical endpoint result or analysis. That makes transparent result reporting crucial: without estimates and uncertainty, the stated research question cannot be answered from the posted record.

The record also highlights the importance of reporting analysis populations, missing-data handling, and multiplicity plans. These details affect how estimates should be interpreted, especially when several outcomes are listed. Their absence does not show that the study was conducted improperly; it means the registry record does not allow readers to evaluate those elements.

Finally, safety counts need context. Zero affected participants in the listed adverse-event categories is a descriptive result, not a complete measure of safety or a comparative risk estimate. Taken together, the study matters statistically as an example of how design, outcome definitions, comparator roles, and completeness of reporting all shape the conclusions readers can draw.

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 important limitation for interpretation is that the registry record does not report numerical results for the primary endpoint. It provides no mean, standard error, change estimate, confidence interval, or p-value for endogenous glucose production. The size, direction, and precision of an observed response therefore cannot be evaluated from the posted results.

The study is classified as single group, with allocation listed as NA and masking listed as none. The control groups are described as baseline references and were not analyzed at the six-month and 18-month time points. The record does not describe a randomized, concurrent comparison. These features limit the extent to which the design can separate an intervention-associated change from other explanations, though the record does not provide results on which to quantify any such change.

The primary outcome timeframe is six months, while the intervention-arm description says participants wore RT-CGM for 18 months. The registry does not provide sufficient detail on all measurement visits or the timing of every analysis to clarify the relationship between these statements. It also does not report participant flow, missing-data methods, analysis populations, or the statistical model.

Although the registry lists four outcome measures, it does not explain how multiple outcomes were handled or whether analyses followed a prespecified hierarchy. No analysis results are listed. The record does not report a statistical analysis plan, sample-size justification, or details of any interim analyses. The planning assumptions described in the record are not a substitute for a full design rationale or evidence of observed power.

Safety reporting is also limited to group-level counts, without event descriptions or further information on ascertainment and follow-up. The record lists zero affected participants in the adverse-event categories, but this alone cannot establish complete event capture. These limitations describe what can be evaluated from the registry record and do not imply that details are unavailable from every other source.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Glucose Counterregulation in Long Standing Type 1 Diabetes — NCT01474889.
• Registry record last updated 2023-08-31; status last verified 2023-08.
• Results first posted 2023-08-31.
• 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 record describes a completed University of Pennsylvania study of RT-CGM and glucose counterregulation in long-standing type 1 diabetes with hypoglycemia unawareness. It records enrollment of 37, a single-group model, and an intervention arm in which participants wore RT-CGM for 18 months. Two control groups are described as baseline references and were not assessed at the six-month and 18-month time points.

The primary outcome is mean endogenous glucose production, measured in mg/kg/min during the final hour of a hypoglycemic clamp, with a six-month timeframe. The registry does not report numerical results or statistical analyses for this endpoint. Its adverse-event record lists zero affected participants for serious and other adverse events and zero deaths in each of the three groups. The record does not provide enough analysis detail to assess missing data, multiplicity, or the precision of the primary outcome.