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 Control-IQ Observational (CLIO) Post-Approval Study (NCT04503174), a registered phase not stated study. The primary outcome is Incidence Rates of Severe Hypoglycemia (SH).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04503174 |
| Phase | Phase not stated |
| Condition | Diabetes Mellitus, Type 1 |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 3157 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Tandem Diabetes Care, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled people with type 1 diabetes. The registry lists groups by age, prior pump or continuous glucose monitor use, and HbA1c category. These labels describe populations of interest, including participants new to insulin pump use, those aged 6-13 years, those aged 14-17 years, adults aged 18 years or older, and participants without recent CGM use. The registry does not report the number of participants in each listed category.
Intervention
The device under study was the t:slim X2 pump with Control-IQ technology. This was a post-approval study of a product described in the registry as cleared by the US FDA. The study was designed primarily to collect safety data. The registry record does not describe a randomized assignment to the device.
Comparator
The registry does not describe a like-for-like control comparison. Allocation is not stated, and the listed groups are population categories rather than a stated randomized comparison. Consequently, the record does not establish a comparison of outcomes between participants assigned to the device and participants assigned to a control intervention.
Primary question
The primary endpoint is the incidence rate of severe hypoglycemia events, expressed as events per 100 patient years over 12 months. The question is descriptive: what overall event rate was recorded during the study exposure? The numerical rate and its standard deviation are not reported in the registry record, so the magnitude and precision of the endpoint cannot be assessed from the posted results.
3. Trial Design
This is a completed post-approval observational study of the t:slim X2 pump with Control-IQ technology. The registry describes it as a 522 study designed primarily to collect safety data on the US FDA-cleared product. It lists an enrollment of 3157 and a study start date of 2020-08-04, with primary completion on 2023-06-02. These dates and enrollment describe the study record; they do not establish how long each participant was followed.
The intervention is the pump with Control-IQ technology. Allocation is not stated, and the registry explicitly indicates that this is not a randomized comparison and that the listed arms are not a like-for-like control comparison. The listed categories include Pump Naive, age groups, CGM Naive, and HbA1c categories. They characterize participants according to prior use or clinical features; the record does not present them as randomized treatment arms.
The primary endpoint concerns the overall incidence rate of severe hypoglycemia events per 100 patient years, with a 12-month timeframe. Secondary outcomes include time in and outside specified glucose ranges and Diabetes Impact and Satisfaction Scale scores. The registry lists 10 outcome measures, but the numerical primary endpoint result and detailed estimates for the secondary outcomes are not reported in the registry record. No analyses are listed. Details such as eligibility criteria, recruitment procedures, the analysis population, participant follow-up completeness, and the statistical analysis plan 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: 3157 participants completed the baseline survey and were enrolled, but only 3061 had started closed-loop and had adequate data available for analysis.
Overall Study
| Stage | All Enrolled Participants |
|---|---|
| STARTED | 3061 |
| COMPLETED | 2998 |
| NOT COMPLETED | 63 |
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 | All Enrolled Participants |
|---|---|---|
| Participants analysed | 3157 | |
| Age, Continuous | years | 29.0 (16.0 to 45.0) |
| Sex: Female, Male: Female | Participants | 1759 |
| Sex: Female, Male: Male | Participants | 1398 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 271 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 2819 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 67 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 60 |
| Race (NIH/OMB): Asian | Participants | 78 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 14 |
| Race (NIH/OMB): Black or African American | Participants | 184 |
| Race (NIH/OMB): White | Participants | 2628 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 67 |
| Region of Enrollment: United States | Participants | 3157 |
6. Primary Endpoint
The registry lists the primary outcome as Incidence Rates of Severe Hypoglycemia (SH), measured over 12 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | events per 100 patient years |
| Endpoint classification | Event-Rate Endpoint |
The primary endpoint is the overall incidence rate of severe hypoglycemia events, expressed as events per 100 patient years, over a 12-month timeframe. An event rate relates the number of events to accumulated time at risk or exposure. Unlike a proportion of participants with at least one event, an event rate can reflect repeated events in the same person. Patient-time provides a common exposure scale when follow-up time varies, though the record does not report how exposure time or recurrent events were handled in the analysis.
As a general statistical concept, rates are useful for describing how frequently events occur relative to observation time. They do not by themselves show how many participants experienced an event, whether events were concentrated in a small number of participants, or how rates compare between treatment groups. Those interpretations require relevant participant-level or comparative information.
The registry identifies the endpoint’s parameter as a mean and its dispersion as a standard deviation. However, the numerical estimate and standard deviation are not reported in the registry record. Without those values, it is not possible to describe the observed rate, its variability, or the precision of the estimate. The endpoint definition also does not specify in the registry record how severe hypoglycemia was defined or adjudicated.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies severe hypoglycemia event incidence as the primary outcome, but it does not report the numerical rate. The stated scale is events per 100 patient years, and the timeframe is 12 months. The record identifies a mean and standard deviation as the parameter and dispersion, but neither the estimate nor its standard deviation is reported. Therefore, the primary outcome cannot be quantified or judged for precision from the posted results.
The study is observational, and allocation is not stated. The record cautions that the listed arms are not a like-for-like control comparison. The age, device-use, CGM-use, and HbA1c labels should therefore be read as descriptions of participant categories, not as evidence of randomized assignment or a controlled treatment contrast. The record does not provide an adjusted or unadjusted comparison estimate, and it lists no analyses.
The registry lists enrollment of 3157. In the adverse-event record, the All Enrolled Participants group has 3061 at risk for serious adverse events and 3061 at risk for other adverse events. These counts are not interchangeable with the enrollment figure. The registry does not explain the difference, so it would be inappropriate to infer why it occurred or how it relates to the primary endpoint population.
For serious adverse events, the record lists 14 affected and 1 death in that group; it lists 0 affected for other adverse events. The listed terms with percentages include Ketosis at 0.3%, Severe Hyperglycemia at 0.1%, Death at 0.0%, and Chest pain at 0.0%. These entries describe the registry’s adverse-event reporting, not the primary endpoint rate. The record does not explain the relationship between the listed term percentages and the event counts, and rounded percentages should not be treated as exact event frequencies.
Overall, the record establishes the study’s observational, post-approval purpose and the outcomes it intended to assess. It does not supply the primary estimate, uncertainty interval, or detailed analyses needed to quantify the primary result or draw a comparative statistical conclusion.
9. Statistical Methods Explained
The registry identifies an event-rate endpoint and gives its scale as events per 100 patient years. It lists a mean as the parameter and standard deviation as the measure of dispersion. These labels describe the intended statistical summary, but the numerical rate and standard deviation are not reported in the registry record. The detailed estimation procedure, model, and handling of repeated events are also not reported in the registry record.
What does an event rate represent?
As a general explanation, an event rate expresses event occurrence in relation to accumulated time at risk or exposure. Patient-time allows observations with different follow-up durations to contribute according to their recorded exposure. A rate can count multiple events for a participant, unlike a simple proportion that counts whether each person did or did not experience at least one event. To interpret a rate fully, readers need to know how the event was defined, how exposure time was accumulated, and how recurrent events were counted. Those details are not reported in the registry record.
What does the stated dispersion measure tell readers?
The registry names the standard deviation as the dispersion measure. In general, a standard deviation describes spread in the values being summarized; it is not the same as a confidence interval and does not, on its own, quantify the precision of an estimated mean. A confidence interval, when reported, gives a range of values compatible with the data under the method used. No confidence interval for the primary endpoint is reported in the registry record. Without a numerical estimate and uncertainty measure, neither the level of observed variation nor the precision of the rate can be assessed.
Why might event-rate data need special modeling?
As a general statistical point, event counts are often analyzed with methods that account for exposure time. Some count data show over-dispersion, meaning that variation exceeds what a simple count model would expect. Over-dispersion can arise when event rates vary across people or when repeated events cluster. A model that accounts for such variation may produce more appropriate uncertainty estimates. The registry record does not report whether over-dispersion was assessed, what model was used, or whether any adjustment for participant characteristics was made. It would be speculation to assign a specific method to this study.
What can the observational design support?
The study is described as observational, and allocation is not stated. As a general principle, observational results can describe events among the participants followed, but comparisons between groups may reflect differences in participant characteristics, care, exposure, or follow-up as well as any intervention-related effects. The registry specifically warns that the listed arms are not a like-for-like control comparison. No causal interpretation or treatment contrast should be inferred from those categories alone. The record does not report an adjustment strategy that might address differences between groups.
What is known about planning assumptions?
The registry describes planning illustrations based on a stated fraction of an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such calculations are hypothetical planning exercises, not observed trial outcomes and not observed power. The registry record does not report a sample-size justification for the study’s own design or numerical planning results in the registry record for interpretation. A planning illustration cannot substitute for the missing primary endpoint estimate, and it cannot establish that a study was adequately powered.
What is missing from the statistical record?
No analyses are listed. The registry does not report the analysis population, missing-data procedures, sensitivity analyses, interim analyses, or a detailed statistical plan. It also does not describe how severe hypoglycemia events were confirmed, how time at risk was determined, or how multiple events within a participant were treated. These omissions limit evaluation of both the endpoint’s construction and its uncertainty. They do not show that a particular method was or was not used; they mean that the method is not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary endpoint and secondary outcomes that include percentages of time in specified glucose ranges and Diabetes Impact and Satisfaction Scale satisfaction and impact scores. It lists 10 outcome measures, but no analyses are listed. The registry record does not report a multiplicity strategy, such as a hierarchy for testing outcomes or an adjustment to account for multiple statistical tests. Without reported analyses and a prespecified testing plan, the role of the secondary outcomes in confirmatory inference is unclear.
Missing-data methods are not reported in the registry record. The record does not state how missing endpoint observations, incomplete follow-up, or unavailable glucose-monitoring data were handled. It also does not describe the analysis population or provide a participant flow accounting for the primary outcome. Consequently, it is not possible to determine whether the reported enrollment corresponds to the people contributing to each endpoint, or how missing information may affect interpretation.
The registry lists 3157 enrolled and 3061 at risk in the adverse-event record. It does not explain the difference, and no inference about its cause is warranted. The primary event-rate result and its uncertainty are not reported. The record also does not report interim analyses or a detailed statistical plan. These omissions limit assessment of selection, missingness, multiplicity, and the statistical treatment of the endpoint; they do not establish that a particular procedure was absent from the study itself.
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 |
|---|---|---|---|
| All Enrolled Participants | 14 | 3061 | 0.5% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| All Enrolled Participants | 1 of 3061 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| All Enrolled Participants | 0 of 3061 |
Most frequent serious adverse event terms
| Event term | Organ system | All Enrolled Participants |
|---|---|---|
| Ketosis | Endocrine disorders | 9 of 3061 |
| Severe Hyperglycemia | Endocrine disorders | 3 of 3061 |
| Death | Cardiac disorders | 1 of 3061 |
| Chest pain | Cardiac disorders | 1 of 3061 |
Serious events with the highest arm-level rate: ketosis (0.3%), severe hyperglycemia (0.1%), death (0.0%), chest pain (0.0%).
The adverse-event record lists an All Enrolled Participants group with 3061 at risk for serious adverse events and 3061 at risk for other adverse events. It reports 14 affected by serious adverse events, 0 affected by other adverse events, and 1 death. These are registry counts for the adverse-event record; they are not the primary severe hypoglycemia event rate and should not be treated as counts of unique participants unless the registry defines them that way.
The registry also lists Ketosis at 0.3%, Severe Hyperglycemia at 0.1%, Death at 0.0%, and Chest pain at 0.0% among the top serious terms. The record does not explain how these term percentages relate to the serious-event count, whether terms may overlap, or how the percentages were rounded. A displayed 0.0% does not establish that no event occurred, particularly because the record also lists 1 death. The relationship between the death count and the term entry is not reported in the registry record.
These figures describe reported safety events in the registry. They do not establish a comparison with a control group or a causal relationship to the device. The registry does not provide the event definitions or detailed ascertainment methods in the record.
12. What the Result Does, and Does Not, Mean
The registry record documents a completed post-approval observational study focused primarily on safety for the t:slim X2 pump with Control-IQ technology. It identifies severe hypoglycemia incidence as the primary endpoint and gives the rate scale and timeframe. It also records adverse-event counts and selected serious-event terms. These details describe what the study was designed to examine and what safety information is listed.
The numerical primary event rate, its standard deviation, and a confidence interval are not reported in the registry record. Therefore, the primary endpoint’s size and precision cannot be evaluated. The study record does not list analyses, and it does not supply comparative estimates for the listed participant categories. No statistical conclusion about a difference between groups can be drawn from the information reported.
The observational design and absence of a stated allocation method also matter. The registry explicitly cautions that the listed groups are not a like-for-like control comparison. Descriptive safety observations do not by themselves show that the device caused or prevented an event. Nor do the registry entries establish how outcomes would compare under a different intervention or in a different population.
The adverse-event figures should be read as registry-reported counts and terms, not as a substitute for the primary endpoint analysis. The record does not explain the discrepancy between enrollment and the adverse-event at-risk count, nor does it give enough information to resolve how event terms and percentages relate to counts. In short, the record identifies the study’s scope and selected safety reporting, but does not provide the endpoint estimates and analysis detail needed for a more complete statistical assessment.
13. Why This Trial Matters Statistically
Post-approval observational studies address a different statistical question from randomized trials. They can collect safety information during use of a cleared product and describe events in the participants observed. This study’s stated primary focus was safety, with severe hypoglycemia incidence selected as its primary endpoint. Its registry record also lists glucose-range and participant-reported outcomes.
The design makes careful interpretation especially important. Allocation is not stated, and the registry says the listed arms are not a like-for-like control comparison. Participant categories based on age, prior pump or CGM use, and HbA1c can help characterize the populations under study, but they do not create randomized contrasts. Descriptive results across such categories would not automatically isolate an intervention effect.
The record also illustrates why an endpoint’s label is not enough to evaluate a result. A rate per 100 patient years requires the event count and exposure time to be understood, while a standard deviation alone would not replace an uncertainty interval. Here, the numerical primary estimate and its uncertainty are not reported in the registry record, and no analyses are listed. Readers therefore cannot assess the rate’s magnitude or precision from the posted information.
Finally, reported safety counts and percentages need context about event definitions, denominators, and analysis populations. The registry lists relevant counts but does not explain all of those details. This makes transparent reporting of methods and estimates central to evaluating post-approval evidence, without implying that missing registry information was necessarily absent from the study’s full records.
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.
Several limitations specific to this study constrain interpretation of the registry record. The design is observational, and allocation is not stated. The registry cautions that the listed arms are not a like-for-like control comparison. The categories by age, pump experience, CGM experience, and HbA1c are not described as randomized comparisons, so they cannot support a direct causal contrast on the basis of the record.
The numerical primary endpoint estimate is not reported in the registry record. Although the endpoint is specified as severe hypoglycemia events per 100 patient years over 12 months and the record identifies a mean and standard deviation, it does not provide the result or an uncertainty interval. No analyses are listed. Detailed methods for event definition, event ascertainment, exposure-time calculation, recurrent-event handling, and adjustment are not reported.
The registry does not describe the analysis population or missing-data procedures. It lists 3157 enrolled, while the adverse-event group lists 3061 at risk; the reason for the difference is not reported. The record does not report a multiplicity approach for the primary and secondary outcomes, an interim-analysis plan, or the statistical analysis plan. It also does not provide numerical results for the secondary outcomes in the information summarized.
These are limitations of what the registry record reports. They do not establish what procedures were or were not carried out beyond the information recorded, but they restrict independent assessment of the study’s estimates and their precision.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Control-IQ Observational (CLIO) Post-Approval Study — NCT04503174.
- Registry record last updated 2023-12-08; status last verified 2023-12.
- Results first posted 2023-12-08.
- 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
The registry record describes NCT04503174, the Control-IQ Observational (CLIO) Post-Approval Study, as a completed observational post-approval study designed primarily to collect safety data on the t:slim X2 pump with Control-IQ technology. It lists enrollment of 3157, with a start date of 2020-08-04 and primary completion on 2023-06-02.
The primary endpoint is the incidence rate of severe hypoglycemia events per 100 patient years over 12 months. The numerical endpoint result and its standard deviation are not reported in the registry record, and no analyses are listed. The registry also lists secondary glucose-range and Diabetes Impact and Satisfaction Scale outcomes.
The adverse-event record lists 14 serious-event affected, 0 other-event affected, and 1 death among the All Enrolled Participants group, with 3061 at risk for each event category. The record cautions that the listed groups are not a like-for-like control comparison.