This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Medtronic MiniMed Implantable Insulin Pump (NCT00298740), a na na study. The primary outcome is Glucose Control as Assessed by Mean Glucose Levels.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00298740 |
| Phase | NA |
| Condition | Type 1 Diabetes |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 12 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Johns Hopkins University |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned people with type 1 diabetes who had previously been implanted with the MiniMed Implantable Pump model 2000 at Johns Hopkins and were then taking insulin by injection. The registry records enrollment of 12. It does not report whether all enrolled participants contributed data to an outcome analysis.
Intervention
The research question concerns reimplantation of implantable insulin pump therapy. The registry’s intervention listing names Aventis U-400 Insulin and categorizes it as a device. The record does not provide further intervention details or explain the relationship between this listing and the pump therapy described in the study summary.
Comparator
No concurrent comparison group is recorded. The study is identified as single-group, with allocation listed as NA and masking as none. The summary describes participants as previously treated with pump therapy and then taking insulin by injection, but this history is not a randomized control arm.
Primary question
The stated primary outcome is glucose control assessed by mean glucose levels at the end of the study, approximately 5 years. The study summary says investigators intended to examine whether pump therapy was associated with more stable glucose control and fewer highs and lows. The registry does not report the mean glucose results, a comparison, or an analysis of that question.
3. Trial Design
This is a completed, single-group study listed under the title Medtronic MiniMed Implantable Insulin Pump. Its official title is Reimplantation of Subjects With Implantable Insulin Pump Therapy. Johns Hopkins University is listed as the sponsor, the condition is type 1 diabetes, and enrollment is recorded as 12. The study start is 2003-02 and primary completion is 2009-09-24. Phase is listed as NA.
The study summary describes people who had previously received implantable insulin pump therapy and were taking insulin by injection, with the research question focused on reimplantation. The registry lists Aventis U-400 Insulin as the intervention and categorizes it as a device. It gives no detailed description of the intervention or of the arm beyond that listing. The registry records no allocation scheme and no masking.
Because the study is single-group, it does not provide a concurrent control group for a like-for-like treatment comparison. A change from an earlier treatment period, if one had been measured, would not by itself separate an intervention effect from changes over time, differences in measurement, or other influences. The record does not report a formal comparison with participants continuing insulin injections.
The primary outcome is titled Glucose Control as Assessed by Mean Glucose Levels, with a timeframe of end of study, approximately 5 years. The registry’s outcome population description states that it is unclear whether data were collected, that no data are available, and that exhaustive searching yielded no person with historical knowledge of the study or access to data. The record says information in other sections came from regulatory records retrieved from long-term storage. It is marked completed, but completion status does not establish that outcome data are available.
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
| Stage | Aventis U-400 Insulin |
|---|---|
| STARTED | 12 |
| COMPLETED | 3 |
| NOT COMPLETED | 9 |
Reasons for not completing this period:
| Reason | Aventis U-400 Insulin |
|---|---|
| Lack of Efficacy | 6 |
| Withdrawal by Subject | 3 |
Analysis population for the primary outcome, as defined in the registry: It is unclear whether data was collected. No data is available and exhaustive searching has yielded no person with historical knowledge of this study or access to any data. Information obtained in other sections was from Regulatory records retrieved from long-term storage. This study closed in 2009 and the Principal Investigator is deceased.
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.
| Characteristic | Unit | Aventis U-400 Insulin |
|---|---|---|
| Participants analysed | 12 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 12 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 4 |
| Sex: Female, Male: Male | Participants | 8 |
| Region of Enrollment: United States | Participants | 12 |
6. Primary Endpoint
The registry lists the primary outcome as Glucose Control as Assessed by Mean Glucose Levels, measured over End of study, approximately 5 years.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is mean glucose levels at the end of the study, approximately 5 years. A mean summarizes the central level of the glucose measurements included in its calculation. It can provide a compact description of glucose control, but by itself it does not describe how widely measurements varied, how often highs or lows occurred, or how those patterns changed during follow-up. The registry does not specify the measurement method, the number or timing of measurements, or the endpoint’s unit.
In general, a mean is useful when a study wants to describe the average level of a quantitative outcome for a defined group and period. Its interpretation depends on how measurements were collected and which participants and observations were included. Variation around the mean and the uncertainty of an estimated mean are also relevant; a single mean cannot show whether individual participants had similar or very different values.
The study summary says investigators wanted to assess more stable glucose control and fewer highs and lows. Mean glucose levels address average level, not stability or the frequency of extremes on their own. The registry does not report the endpoint result, its dispersion, an analysis population, or an estimate of uncertainty. It is therefore not possible to determine from this record what average was observed or how precisely it was estimated.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The key interpretive fact is that the registry lists a primary endpoint but supplies no outcome measurements or analysis results. It reports no mean glucose level, no estimate of change, no measure of variability, no confidence interval, and no test result. The endpoint’s population description explicitly says that it is unclear whether data were collected and that no data are available. Consequently, the record does not establish the direction or size of any observed glucose difference.
The single-group design also limits what a result could establish. Without a concurrent control group, an outcome measured after reimplantation could describe the participants at that time, but a difference from an earlier period would not, on its own, show that the intervention caused the difference. Changes in participants, measurement procedures, or other conditions could contribute. The registry does not report a prespecified comparison with the earlier injection period or another control condition.
The stated endpoint is mean glucose at the end of the study, approximately 5 years. The summary’s broader interest in stable control and fewer highs and lows is not fully represented by a mean alone. Even if an average had been reported, additional information about measurement variability and glucose extremes would be needed to describe those aspects of control. No such endpoint results are available in the registry record.
Enrollment is recorded as 12, but this number does not show how many participants had evaluable endpoint measurements. The record does not identify an analysis population, explain participant follow-up, or describe missing outcome data. It would therefore be inappropriate to assume that all enrolled participants contributed to an analysis or that the recorded enrollment is the denominator for the primary endpoint.
The study status is completed, while its outcome description says that data availability is unclear and no data are available. These statements can coexist: a registry may record that a study closed without having results accessible in the record. The adverse-event information is separate from the missing primary outcome. It reports safety counts, including one death, but those counts do not provide evidence about the mean-glucose endpoint or explain why the study ended.
Overall, the registry supports a description of the research question, design, and limited safety reporting. It does not support an estimate of the intervention’s effect on mean glucose, a claim about the precision of such an estimate, or a causal conclusion. The absence of posted outcome results is not evidence that the endpoint was unchanged; it means the endpoint cannot be evaluated from the available record.
9. Statistical Methods Explained
What does the single-group design imply?
A single-group study describes outcomes in participants receiving the study intervention without a concurrent comparison group. In general, this design can document what was observed among participants, but it has limited ability to separate an intervention’s effect from other influences. A comparison with participants’ earlier experience is not equivalent to a concurrent control: time, measurement, and participant circumstances may differ between periods. This registry identifies the study as single-group and gives no randomized or concurrent comparator.
The record lists allocation as NA and masking as none. Those entries do not describe an allocation procedure or blinded outcome assessment. The registry does not report further details about how the intervention was assigned, how measurements were obtained, or whether any outcome assessor was independent. These methods cannot be inferred from the study title or summary.
What does a mean glucose endpoint capture?
In general, a mean is a measure of central tendency: it summarizes the average of the values included in its calculation. Its meaning depends on which values were collected, when they were collected, and which participants contributed them. The registry names mean glucose levels as the primary outcome but does not report its unit, measurement schedule, or calculation details. It also does not report an observed mean or a measure of dispersion, such as a standard deviation.
An estimated mean is usually interpreted alongside uncertainty. In general, a confidence interval describes a range of values compatible with the data and the specified statistical method; it is not a guarantee that the true value lies in that range. A narrow interval indicates greater precision than a wide interval under the same framework. Here, no estimate or interval is reported, so neither the endpoint’s magnitude nor its precision can be assessed.
Why does a control group matter?
In general, a concurrent control group helps distinguish outcome changes associated with an intervention from changes that might have occurred without it. Random allocation, when used and properly implemented, can help make groups comparable on average. This record does not describe randomized allocation or a concurrent comparator. The earlier use of insulin injections described in the study summary is part of the participants’ history, not a registry-reported control arm.
A before-and-after comparison, if it had been conducted, would require both measurements and a clear analysis plan. The registry does not report such measurements, an analysis, or a statistical contrast between periods. There is therefore no basis in this record for treating participants’ prior treatment as a control condition or attributing a possible difference to reimplantation.
What can be said about statistical testing?
The registry reports zero analyses and gives no primary-outcome estimate or test result. No p-value, confidence interval, model, or adjustment method is reported. A p-value, in general, measures how unusual data at least as extreme as the observed data would be under a specified null model; it does not measure the size or clinical importance of an effect. Since no test result or analysis method is available, statistical significance cannot be assessed.
The registry does describe assumptions for planning illustrations: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. It also distinguishes total-event planning for time-to-event outcomes from participants-per-arm planning for other outcomes. These are planning assumptions, not a report of the study’s original design or an observed treatment effect. The registry does not report an observed primary-outcome effect from which such an illustration could be interpreted, and it does not state that these assumptions governed the study itself.
In general, over-dispersion matters when count data vary more than a model’s assumed distribution allows; ignoring it can make uncertainty estimates too small. That concept does not supply an analysis for this study. The listed primary endpoint is a mean, and no count model or other endpoint model is reported.
What is the role of sample-size planning?
In general, sample-size planning uses assumptions about the outcome, variability, design, and target effect to illustrate how much information a study might collect. A planning illustration is not evidence that a study had a particular probability of detecting an effect, and it is not an observed result. It should not be confused with observed power, which cannot substitute for reporting an estimate and its uncertainty.
The planning assumptions stated in the registry describe a hypothetical equal-allocation, two-arm calculation, while the registered study is single-group. This mismatch means the assumptions should not be read as the design of the completed study. The registry does not report the study’s own sample-size justification or a primary-outcome estimate that would allow readers to connect those assumptions to the observed study. Enrollment of 12 alone is not enough to evaluate precision or statistical power.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure, mean glucose levels at the end of the study, approximately 5 years. It reports zero analyses and no outcome results. The record does not describe a statistical analysis plan, a hierarchy of hypotheses, any secondary outcomes, or how multiple comparisons would have been handled. It is therefore not possible to determine whether multiplicity was relevant to the analyses actually conducted or whether any adjustment was planned.
Missing-data handling is also not reported. The primary outcome population description says that it is unclear whether data were collected and that no data are available. There is no account of participant follow-up, missing measurements, reasons for missingness, exclusions, or any method for handling incomplete outcome data. The recorded enrollment of 12 should not be treated as the number analyzed for mean glucose.
The registry does not identify an intention-to-treat, per-protocol, or other analysis population. It does not explain whether participants were included according to enrollment, intervention exposure, or endpoint availability. Without these details, the population to which any hypothetical outcome estimate would apply cannot be specified. The record’s statement that the study closed in 2009 does not resolve these analytic omissions.
In general, multiplicity concerns arise when multiple hypotheses or outcomes are tested, because interpreting each test independently can increase the chance of a misleading finding. Missing-data methods can also affect estimates, especially when the likelihood of missingness is related to participant characteristics or outcomes. These are general statistical considerations; the registry does not report enough information to determine how either issue was addressed in this study.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Aventis U-400 Insulin | 1 | 12 | 8.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Aventis U-400 Insulin | 1 of 12 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Aventis U-400 Insulin | 12 of 12 |
Most frequent serious adverse event terms
| Event term | Organ system | Aventis U-400 Insulin |
|---|---|---|
| Death | Cardiac disorders | 1 of 12 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Aventis U-400 Insulin |
|---|---|---|
| Pump explant | Product Issues | 6 of 12 |
| Fracture | Musculoskeletal and connective tissue disorders | 3 of 12 |
| Hyperglycemia | Endocrine disorders | 3 of 12 |
| Hypoglycemia | Endocrine disorders | 2 of 12 |
| Rectal hemorrage | Gastrointestinal disorders | 1 of 12 |
| Left lower quadrant pain | Gastrointestinal disorders | 1 of 12 |
| Right groin pain | Musculoskeletal and connective tissue disorders | 1 of 12 |
| Right shoulder pain | Musculoskeletal and connective tissue disorders | 1 of 12 |
| Poison ivy | Skin and subcutaneous tissue disorders | 1 of 12 |
| Cataract surgery | Surgical and medical procedures | 1 of 12 |
Serious events with the highest arm-level rate: death (8.3%).
The registry reports one participant with a serious adverse event among 12 at risk in the Aventis U-400 Insulin group. It reports 12 participants at risk for other adverse events and 12 affected. The recorded number of deaths is 1, and Death is listed as the top serious term at 8.3%. These are the safety figures recorded for the study group.
These counts describe reported events in a small single-group record; they do not establish that the intervention caused an event. The registry does not provide event narratives, timing, severity details beyond the serious-event classification, or an assessment of relatedness. It does not state whether the death was judged related to the intervention. The safety counts also do not replace the missing primary glucose outcome.
In general, adverse-event counts are interpreted in light of how events were defined, collected, and attributed, as well as the duration of observation. The record does not provide enough detail to assess those factors. The percentage 8.3% is quoted as recorded; it is not a measure of comparative risk because no control group is listed.
12. What the Result Does, and Does Not, Mean
The registry establishes that a completed single-group study was registered to examine reimplantation of implantable insulin pump therapy in people with type 1 diabetes who had previously used the MiniMed Implantable Pump model 2000 and were taking insulin by injection. It records enrollment of 12 and identifies mean glucose levels at the end of the study, approximately 5 years, as the primary outcome. It also records limited adverse-event counts.
It does not establish what mean glucose level was observed, whether glucose changed over time, or how precisely any estimate was measured. The outcome description states that data availability is unclear and that no data are available. No statistical analysis results are reported. The record therefore cannot support a conclusion that glucose control improved, worsened, or remained unchanged.
The design does not include a concurrent control group. Even if a within-participant change had been reported, it would not by itself establish that reimplantation caused the change. A comparison to prior injection treatment would be vulnerable to differences between periods and other influences. The registry does not report such a comparison in any case.
The summary describes an interest in more stable control and fewer highs and lows, while the primary outcome is mean glucose. A mean can describe average level, but it does not fully characterize variability or extremes. The registry reports no additional glucose measures that would answer those broader questions.
The safety figures should be read as recorded event counts, not as proof of causation or comparative safety. The available record gives no basis for attributing the death or other events to the intervention. In general, conclusions about treatment effects require interpretable outcome data, a clear analysis, and a design suited to the question. Those elements are not available for the primary endpoint in this record.
13. Why This Trial Matters Statistically
This study raises an important statistical distinction between registering a clinical question and having results that can answer it. The registry preserves a clear general aim—examining glucose control after reimplantation—but its primary outcome description says that data availability is unclear and that no data are available. Without outcome measurements, the central statistical task of estimating the mean and its uncertainty cannot be carried out from this record.
The design also illustrates why the comparison structure matters. The study is single-group, with no concurrent control. A treatment history can be informative context, but it is not automatically a valid counterfactual. For causal interpretation, researchers need a design and analysis that address what might have happened to the same population without the intervention. The registry does not report such a comparison.
There is also a useful distinction between an outcome label and a complete endpoint definition. Mean glucose levels are named, but the unit, measurement schedule, calculation details, analysis population, and variability are not reported. Those details affect what the mean represents and how readers should understand its precision. A mean alone would not directly answer the stated interest in stability or highs and lows.
Finally, planning assumptions should not be mistaken for trial results or for evidence about the completed design. The registry describes hypothetical planning assumptions involving two arms, while identifying this study as single-group. Such assumptions cannot fill the gaps left by absent outcome data or establish that the original study was designed or analyzed in that way.
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 interpretation is the absence of primary outcome data. The registry states that it is unclear whether data were collected and that no data are available. It reports no mean glucose result, dispersion, confidence interval, or statistical test. The primary question therefore cannot be answered from the record.
The design is single-group, with no concurrent control and no allocation procedure described. The registry does not report an analysis comparing outcomes during pump therapy with outcomes during insulin injections. It is not possible to assess a causal effect or separate an intervention-associated change from other changes over time.
The endpoint description is incomplete for statistical interpretation. The unit, measurement method, schedule, calculation details, and analysis population are not reported. Nor does the record say how many participants contributed endpoint data, whether measurements were repeated, or how missing values were handled. Enrollment of 12 does not establish the number included in an outcome analysis.
The stated primary outcome is a mean, while the study summary also refers to stability and fewer highs and lows. No separate measure of variability or glucose extremes is reported. The record also does not provide a statistical analysis plan, sample-size justification for the registered design, or details about multiplicity. The listed planning assumptions describe a two-arm illustration and should not be taken as the protocol for this single-group study.
Safety information is limited to aggregate counts and a serious-event term. Event timing, narratives, relatedness, and follow-up duration are not reported. These omissions restrict interpretation of both the efficacy question and the safety record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Medtronic MiniMed Implantable Insulin Pump — NCT00298740.
- Registry record last updated 2017-09-12; status last verified 2017-09.
- Results first posted 2017-09-12.
- 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.
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18. Record Summary
NCT00298740 is a completed, single-group study sponsored by Johns Hopkins University, with enrollment recorded as 12 and type 1 diabetes listed as the condition. Its title is Medtronic MiniMed Implantable Insulin Pump, and the official title is Reimplantation of Subjects With Implantable Insulin Pump Therapy. The study summary describes people previously treated with implantable insulin pump therapy who were taking insulin by injection. Aventis U-400 Insulin is listed as the intervention and categorized as a device.
The primary outcome is mean glucose levels at the end of the study, approximately 5 years. The registry reports no outcome data or analyses and says it is unclear whether data were collected. No concurrent control group is recorded. Safety reporting includes one serious adverse event affected participant, 12 affected participants for other adverse events, one death, and Death listed as a serious term at 8.3%. The record does not report a primary-outcome result or an analysis that supports an estimate of effect.