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 Diabetes Pump With Predictive Low Glucose Suspend Pivotal Trial (NCT03195140), a randomized na study. The primary outcome is Hypoglycemia < 70 mg/dL.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03195140 |
| Phase | NA |
| Condition | Diabetes Mellitus, Type 1 |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 103 |
| Arms in the primary outcome | 3 |
| Lead sponsor | Tandem Diabetes Care, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled adults and youth > 6 years old with type 1 diabetes. The registry lists an enrollment of 103 participants. For the primary endpoint and the posted secondary summaries, each reported group has 102 participants; the registry record does not explain the difference between these counts or specify the analysis population.
Intervention
The intervention was predictive low glucose suspend (PLGS), using a Tandem pump integrated with Dexcom G5 continuous glucose monitoring and a predictive suspend feature. The registry describes the device as the t:slim X2 with Basal-IQ Technology.
Comparator
The comparator was sensor-augmented pump therapy (SAP) using an otherwise functionally identical Tandem pump without the PLGS feature and associated user interface. The registry identifies this device as the t:slim X2 Dexcom G5 Mobile CGM Enabled pump.
Primary question
The primary question was whether time with continuous glucose monitoring readings below 70 mg/dL differed during PLGS use and SAP use. The primary outcome is expressed as a percentage of time, with a 3-week timeframe for each reported outcome period. The posted primary values are medians and inter-quartile ranges; a formal comparative estimate, confidence interval, and p-value are not reported in the registry record.
The registry describes a 6-week crossover study. In a crossover design, participants receive the compared conditions at different times, so each participant can contribute observations under both conditions. That structure makes the within-participant contrast important to interpretation. The registry record identifies the design as crossover but does not report the sequence, period-specific analysis, or other details needed to assess how the paired observations were handled.
3. Trial Design
This was a randomized, open-label crossover trial sponsored by Tandem Diabetes Care, Inc. The registry lists the trial as completed, with 103 participants enrolled. The study began on 2017-08-11 and reached primary completion on 2018-02-06. Its brief description characterizes it as a 6-week comparison of PLGS and SAP outcomes in adults and youth > 6 years old with type 1 diabetes.
Randomization means assignment to the treatment sequence was intended to use a chance-based process. The registry lists no masking, so the trial was not described as blinded. In a crossover design, the same participants can contribute outcome information under each treatment condition. This can make within-participant comparisons informative, but it also means analysis should account for the relationship between a participant’s measurements in the different periods. The registry record does not report the treatment sequence, any washout arrangement, or the method used to model within-participant measurements.
The PLGS condition used a Tandem ambulatory insulin infusion pump integrated with Dexcom G5 continuous glucose monitoring and predictive low glucose suspend. The SAP condition used a pump described as identical in functionality except that it lacked the PLGS feature and its associated user interface. Both are described as device interventions, and the registry identifies type 1 diabetes as the condition under study.
The registry reports 102 participants for each primary-outcome group and for the two secondary outcomes with detailed summaries. Safety groups list 103 participants at risk in each condition. These counts describe the posted results; the registry record does not state the reason for the differing denominators, define a modified or per-protocol population, or explain which participants contributed to each analysis. No sample-size justification or detailed statistical analysis plan is reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | PLGS First, Then SAP | SAP First, Then PLGS |
|---|---|---|
| STARTED | 52 | 51 |
| COMPLETED | 52 | 51 |
| NOT COMPLETED | 0 | 0 |
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 | PLGS First, Then SAP | SAP First, Then PLGS | Total |
|---|---|---|---|---|
| Participants analysed | 52 | 51 | 103 | |
| Age, Categorical: <=18 years | Participants | 29 | 31 | 60 |
| Age, Categorical: Between 18 and 65 years | Participants | 22 | 19 | 41 |
| Age, Categorical: >=65 years | Participants | 1 | 1 | 2 |
| Age, Continuous | years | 25 (SD 18) | 23 (SD 16) | 24 (SD 17) |
| Sex: Female, Male: Female | Participants | 26 | 32 | 58 |
| Sex: Female, Male: Male | Participants | 26 | 19 | 45 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 3 | 4 | 7 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 49 | 47 | 96 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 2 | 1 | 3 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 2 | 2 |
| Race (NIH/OMB): White | Participants | 44 | 38 | 82 |
| Race (NIH/OMB): More than one race | Participants | 2 | 6 | 8 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 3 | 4 | 7 |
| Region of Enrollment: United States | Participants | 52 | 51 | 103 |
6. Primary Endpoint
The registry lists the primary outcome as Hypoglycemia < 70 mg/dL, measured over 3 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | percentage of time |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is hypoglycemia below 70 mg/dL, measured as the percentage of time continuous glucose monitoring readings were below that threshold. The registry gives a 3-week timeframe and reports the endpoint as a median with an inter-quartile range. The measure describes how much of the monitored time fell in the defined low-glucose range, rather than counting only the number of discrete events.
As a general statistical point, a percentage-of-time outcome uses repeated measurements over a monitoring period to describe exposure to a range of values. A median represents the center of the observed distribution, while the inter-quartile range describes the span from the lower to the upper quartile. These summaries are useful when a distribution may not be well represented by a mean and standard deviation. They do not, on their own, show the uncertainty in a comparison between treatment conditions.
The registry reports a median of 3.6 with an inter-quartile range of 1.9 to 5.6 at baseline, 2.6 with an inter-quartile range of 1.4 to 4.0 in the intervention arm, and 3.2 with an inter-quartile range of 1.9 to 6.1 in the control arm. These are descriptive results. A treatment contrast based on the crossover participants, its confidence interval, and its p-value are not reported in the registry record. Therefore, the posted medians and quartiles describe the observed distributions but do not establish the precision of a PLGS-versus-SAP contrast.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome is summarized by medians and inter-quartile ranges. The posted median was 2.6 in the intervention arm and 3.2 in the control arm, while baseline was 3.6. The quartile ranges were 1.4 to 4.0, 1.9 to 6.1, and 1.9 to 5.6, respectively. These summaries describe the distribution of time below 70 mg/dL in each reported group. They should not be treated as a direct estimate of the randomized crossover treatment effect: the registry does not post a paired contrast, confidence interval, or p-value for the primary endpoint.
The secondary outcomes with numerical summaries include time in range from 70 to 180 mg/dL and time above 180 mg/dL. The registry reports means and standard deviations for baseline, intervention, and control. Recalculated unadjusted comparisons against control give mean differences of 1.0 for baseline and 2.0 for intervention on time in range; their 95% confidence intervals are -3.117 to 5.117 and -2.117 to 6.117, with unadjusted p-values of 0.634 and 0.341. For time above 180 mg/dL, both recalculated mean differences are -1.0. Their 95% confidence intervals are -5.531 to 3.531 and -5.256 to 3.256, with unadjusted p-values of 0.665 and 0.645. Each interval includes zero, so these simple comparisons do not precisely distinguish the summarized means.
These recalculations are not the trial sponsor’s reported inferential analyses. The registry lists zero reported analyses, and the secondary summaries do not include reported analyses. The recalculated comparisons use posted summary statistics and are unadjusted. In particular, they do not incorporate the paired structure expected from a crossover trial. Their confidence intervals and p-values should therefore be read as exploratory descriptions of the posted summaries, not as a substitute for a crossover-specific analysis.
The sample-size planning illustrations are also conditional rather than confirmatory. They use the observed effects as starting points and consider specified fractions of those effects under stated assumptions. They are not the trial’s sample-size justification, which is not reported in the registry record, and they are not observed power. They cannot establish whether the trial was adequately powered for its primary comparison.
Overall, the registry provides descriptive primary summaries and limited secondary numerical summaries, but not a reported inferential analysis of the primary endpoint. The posted results support describing what was observed in the summarized groups; they do not quantify the uncertainty around the central crossover comparison. The distinction matters because an apparent difference between group summaries is not itself evidence that a treatment contrast is statistically precise.
9. Statistical Methods Explained
Several statistical ideas help distinguish what the posted numbers describe from what they can establish. The registry identifies a randomized crossover design, while the posted outcomes are group summaries. A crossover trial collects information under more than one treatment condition from participants, so the treatment contrast naturally depends on within-participant differences. Measurements from the same person are generally related. A method that treats them as independent can misstate uncertainty because it does not use that pairing.
What do the descriptive summaries tell us?
The primary outcome is reported as a median and inter-quartile range. The median is the middle value in an ordered set of observations. The inter-quartile range gives the lower and upper quartiles and describes the spread of the middle half of observations. These statistics show the center and dispersion of the observed endpoint distribution, but they do not quantify uncertainty in a difference between conditions. In particular, overlapping or non-overlapping quartile ranges are not a replacement for a treatment-effect estimate and its confidence interval.
The secondary continuous outcomes are reported as means and standard deviations. A mean gives the arithmetic average, and a standard deviation describes variability around that mean. These summaries permit simple recalculation of mean differences, but they do not include the participant-level pairing needed for a crossover analysis. The recalculated comparisons are unadjusted and should be regarded as approximate descriptive comparisons based on the posted summaries, not as sponsor-reported trial analyses.
How should a confidence interval be read?
A confidence interval gives a range of values compatible with the data under the method used to calculate it. A wide interval indicates substantial uncertainty about the size and direction of the estimated contrast; an interval that includes zero does not clearly distinguish a positive from a negative mean difference under that calculation. The secondary confidence intervals are recalculated from posted summary statistics, not reported crossover-specific intervals. No confidence interval for the primary endpoint is reported in the registry record.
A p-value measures how unusual the data would be under a specified null hypothesis and analysis model. It is not the probability that the null hypothesis is true, nor does it measure clinical importance. The posted secondary p-values are unadjusted recalculations. Because multiple secondary outcomes are listed, interpreting each p-value as if it were the only statistical test can overstate the strength of evidence. The registry record does not report a multiplicity adjustment or a hierarchy for interpreting secondary tests.
What does the sample-size planning illustration mean?
The planning illustration states assumptions of a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It considers effects at 100%, 75%, and 50% of the observed effect and gives participants per arm for 80% and 90% power. These are planning illustrations, not observed power and not evidence about the actual design calculation. The trial’s own sample-size assumptions and justification are not reported in the registry record.
General statistical principle: a planning calculation estimates the sample size that would be needed under its assumed effect, variability, allocation, and testing method. If the assumed effect is smaller, more participants are generally needed to detect it with the same target power. Such a calculation is only as relevant as its assumptions. The posted illustration uses a two-arm framework and summary-statistic inputs; it does not represent a crossover-specific sample-size calculation unless the model accounts for within-participant correlation, which is not reported.
Why does the crossover structure matter?
In a crossover design, the treatment effect is usually informed by the difference within each participant across conditions. This can account for stable differences between participants and may affect the precision of the estimate. Period effects, treatment sequence, and other design features can also matter. The registry identifies the crossover structure but does not report details of the statistical model, sequence, period effects, or handling of repeated measurements. Consequently, the simple recalculated secondary contrasts do not reproduce a documented trial analysis.
There is no reported sponsor analysis to compare with the simple recalculations: the registry lists zero reported analyses. The registry record also does not report a primary-endpoint confidence interval, standard error, test statistic, or p-value. The appropriate reading is therefore descriptive for the primary outcome and exploratory for the recalculated secondary comparisons. A more complete statistical interpretation would require the protocol or analysis report, including the prespecified estimand, analysis population, handling of missing observations, and crossover-specific model.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 11 outcome measures, including the primary endpoint and secondary outcomes addressing different aspects of glucose exposure. It posts ten secondary outcomes, while detailed numerical summaries are present for only a subset. The record lists zero reported analyses. It does not describe a testing hierarchy, identify a family of confirmatory secondary hypotheses, or report an adjustment for multiple comparisons. Multiplicity handling is therefore not reported in the registry record.
As a general statistical principle, when many outcomes or hypotheses are examined, the chance of at least one nominally unusual result can increase. Adjusting for multiplicity can help control that risk, but the appropriate method depends on which comparisons were planned and which claims are intended to be confirmatory. The unadjusted recalculated secondary p-values do not account for the number of outcomes or comparisons. They should not be interpreted as if each were the sole planned test.
Details about missing data are also not reported in the registry record. The primary and detailed secondary summaries list 102 participants per group, whereas enrollment is 103 and safety groups list 103 at risk per condition. The record does not explain these denominators, report how many measurements were missing, state whether participants with incomplete monitoring were excluded, or describe an imputation or sensitivity analysis. It is not possible to determine from the posted information whether the analyzed observations represent all randomized participants or a subset defined by data availability.
The registry record does not define an intention-to-treat, per-protocol, or other analysis population. Nor does it report how the randomized sequence, period effects, repeated measurements, or within-participant correlation were handled. These omissions limit the ability to evaluate whether the analysis preserves the design and how robust the results are to missingness or alternative analysis choices. They do not prove that the trial lacked such procedures; those details are simply not reported in the registry record.
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 |
|---|---|---|---|
| Intervention Arm | 0 | 103 | 0.0% |
| Control Arm | 2 | 103 | 1.9% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Intervention Arm | 0 of 103 |
| Control Arm | 0 of 103 |
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 |
|---|---|
| Intervention Arm | 58 of 103 |
| Control Arm | 59 of 103 |
Most frequent serious adverse event terms
| Event term | Organ system | Intervention Arm | Control Arm |
|---|---|---|---|
| Bowel Obstruction | Gastrointestinal disorders | 0 of 103 | 1 of 103 |
| Severe Hypoglycemia | Endocrine disorders | 0 of 103 | 1 of 103 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Intervention Arm | Control Arm |
|---|---|---|---|
| Ketosis | Endocrine disorders | 58 of 103 | 59 of 103 |
Serious events with the highest arm-level rate: bowel obstruction (1.0%), severe hypoglycemia (1.0%).
The registry lists 103 participants at risk in each treatment condition. It reports zero serious adverse events affecting participants in the intervention arm and 2 in the control arm. Deaths are listed as 0 in both conditions. Other adverse events affected 58 participants in the intervention arm and 59 in the control arm. These are counts of participants recorded as affected, not a comparative estimate of risk.
The serious-event terms listed are bowel obstruction and severe hypoglycemia, each reported as 1.0%. The registry excerpt does not assign these terms to a particular treatment condition, so they should not be attributed to either arm from these figures alone. Nor does the record provide a formal safety comparison, confidence interval, or statistical test. The counts are descriptive and do not establish whether any difference between conditions is meaningful.
Safety counts need to be read with the trial’s crossover structure and the registry’s reporting detail in mind. The record does not explain whether events are assigned by period, whether the same participant could contribute events under different conditions, or how exposure time was considered. Those details are not reported in the registry record. The posted figures therefore describe recorded adverse-event counts and affected participants, without supporting a causal conclusion about differences in safety.
12. What the Result Does, and Does Not, Mean
The registry results describe measurements collected in a randomized crossover study of PLGS and SAP. For the primary endpoint, the record reports medians and inter-quartile ranges for time below 70 mg/dL. For two secondary outcomes, it reports means and standard deviations, alongside simple recalculated comparisons. These figures provide a snapshot of the posted summaries, but they are not a complete inferential analysis of the crossover treatment contrast.
The primary outcome does not have a reported comparative estimate, confidence interval, or p-value in the registry record. The secondary confidence intervals and p-values are unadjusted recalculations from posted group summaries, rather than the sponsor’s reported analysis. They do not use a documented crossover-specific method, and the registry does not report how missing measurements or repeated observations were handled. The results therefore do not establish the precision of the primary treatment contrast or resolve uncertainty about it.
These limits do not mean the trial had no protocol, analysis plan, or additional analyses. They mean that those details and results are not reported in the registry record. Likewise, the descriptive summaries should not be read as evidence that one treatment is better or worse. They state what was recorded in the listed groups; they do not show the treatment effect with enough inferential detail to support a definitive conclusion.
The planning illustrations answer a different question: under stated assumptions, how many participants per arm might be needed to detect specified fractions of observed effects at target power levels. They are not observed power, do not demonstrate that the trial was designed around those assumptions, and do not compensate for the absence of a reported crossover analysis. The trial’s own sample-size rationale is not reported in the registry record.
In short, the registry permits descriptive reading of selected primary, secondary, and safety outcomes. A fuller assessment of the treatment contrast would require the prespecified analysis and participant-level or crossover-specific results, including estimates of uncertainty and the handling of missing data and multiple outcomes. Without those details, the posted statistics should be interpreted narrowly.
13. Why This Trial Matters Statistically
This trial is statistically interesting because its crossover design and registry summaries call for different levels of interpretation. A crossover trial can use each participant’s experience under both conditions, but that design feature is useful only when the analysis accounts for within-participant dependence. The registry identifies the crossover model, yet it does not report the analysis method or a paired estimate for the primary endpoint. This makes the distinction between descriptive group summaries and a design-aligned treatment contrast especially important.
The primary endpoint is a median-based measure of time below a glucose threshold. Medians and inter-quartile ranges are appropriate descriptive tools for distributions that are not well represented by averages, but they do not provide a confidence interval for the difference between conditions. Readers therefore need to avoid treating a change in the displayed group medians as a precise estimate of the crossover effect.
The secondary outcomes also illustrate why analysis provenance matters. Their posted means and standard deviations permit simple recalculations, but those results are unadjusted and do not account for the crossover pairing. They also arise among multiple outcomes, with no reported multiplicity strategy. A numerical p-value alone cannot resolve either issue.
Finally, planning illustrations derived from observed effects can help show how assumptions about effect size affect sample-size requirements. They do not establish the trial’s original design rationale or the probability that the trial detected an effect. Keeping planning calculations separate from observed results, and keeping descriptive summaries separate from sponsor analyses, is essential for transparent interpretation of clinical trial statistics.
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 are specific to the posted record. First, the primary endpoint is reported descriptively, without a comparative estimate or uncertainty interval. The medians and inter-quartile ranges do not show how precisely the intervention and control conditions differ under the randomized crossover design.
Second, the detailed secondary comparisons are simple unadjusted recalculations from group summaries. They do not use reported participant-level paired data or a documented crossover-specific model. Because the study is identified as a crossover trial, this leaves uncertainty about whether the comparisons reflect the design’s within-participant information. The record does not report treatment sequence, period effects, or the handling of repeated measurements.
Third, the secondary outcomes are numerous, while the registry does not report a multiplicity procedure or specify which outcomes were intended to be confirmatory. Numerical results for only a subset of posted secondary measures are included in the detailed summaries; values for other endpoint comparisons are missing or not estimable as two-arm comparisons. A complete secondary-outcome analysis is not reported in the registry record.
Fourth, the analyzed denominators and missing-data procedures are unclear. The registry reports enrollment of 103, outcome summaries with 102 per group, and 103 at risk in each safety group, but does not explain the difference or define the analysis populations. Missing observations, exclusions, imputation, and sensitivity analyses are not reported in the registry record.
Finally, the record does not report the trial’s sample-size justification or a full statistical analysis plan. The planning illustrations based on observed effects are not substitutes for those design documents. These limitations describe gaps in the registry reporting; they do not establish that the trial team did not conduct additional analyses.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Diabetes Pump With Predictive Low Glucose Suspend Pivotal Trial — NCT03195140.
- 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
NCT03195140 is the completed Tandem PLGS Pivotal Trial, a randomized, open-label crossover study in adults and youth > 6 years old with type 1 diabetes. The registry lists 103 enrolled participants and compares predictive low glucose suspend with sensor-augmented pump therapy.
The primary outcome is percentage of time with continuous glucose monitoring readings below 70 mg/dL over 3 weeks, reported as medians and inter-quartile ranges. A formal comparative estimate and uncertainty interval for this endpoint are not reported in the registry record. Detailed numerical summaries are posted for two secondary outcomes; the simple recalculations are unadjusted and do not account for the crossover pairing.
The record lists zero reported analyses. Details of the statistical plan, analysis populations, missing data, and multiplicity handling are not reported in the registry record. Safety counts are descriptive, with no deaths listed in either condition.