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 Duration of Infusion Set Function: Quick-Set Teflon Catheter Versus Sure-T Steel Infusion Set Catheter (NCT01288729), a randomized na study. The primary outcome is Length of Wear of Infusion Site.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01288729 |
| Phase | NA |
| Condition | Diabetes Mellitus |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 20 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Stanford University |
| Results posted | Yes |
2. Clinical Question
Population
Participants with Diabetes Mellitus who took part in the trial. The registry reports an enrollment of 20 and says that participants with available data were analyzed. The outcome counts are 19 for the Sure-T Steel Infusion Set Catheter and 20 for the Quick-Set Teflon Catheter.
Intervention
Use of the Quick-Set Teflon Catheter, with wear duration recorded in hours. The study description says participants wore each set for up to 7 days twice.
Comparator
Use of the Sure-T Steel Infusion Set Catheter, also assessed by length of wear in hours. This was an active device comparison, not a comparison with no infusion set.
Primary question
How does the length of wear of the Sure-T Steel Infusion Set Catheter compare with the length of wear of the Quick-Set Teflon Catheter over the reported 5 weeks? The registry reports the outcome separately by intervention, using medians and interquartile ranges.
The question concerns duration of infusion-site wear, rather than a clinical outcome such as blood glucose or a measure of quality of life. The registry notes that infusion sets are approved for wear 2-3 days (24-72 hours), while participants in this study could wear each set for up to 7 days. That describes the trial's measurement context; the registry record does not state that every set reached the maximum wear duration.
The study is described as an open-label crossover comparison. In a crossover design, a participant may receive or use more than one study condition over time, so a comparison can potentially use observations from the same participant under both conditions. The record's outcome summaries, however, are presented by intervention. They do not report a paired comparison or explain how the crossover structure was handled in analysis. The registry's group descriptions also contain a sequence inconsistency, discussed in the trial-design account.
3. Trial Design
The registry describes a randomized, open-label crossover study sponsored by Stanford University. The condition is Diabetes Mellitus, enrollment is 20, and the study status is completed. The phase is listed as NA. The start is recorded as 2011-01 and primary completion as 2011-07.
The two devices were the Sure-T Steel Infusion Set Catheter and the Quick-Set Teflon Catheter. The stated study timeframe for the primary outcome is 5 weeks. The summary says participants wore each set for up to 7 days twice. The design is described as alternating between device types, with participants assigned to different starting sequences.
The sequence descriptions are not fully consistent. The first group is titled as steel followed by Teflon, and its description says participants alternate between the Sure-T Steel set for 7 days and the Quick-Set Teflon set for 7 days, wearing each set twice and starting with steel. The second group is titled as Teflon then steel, but its description says participants alternate between the Quick-Set Teflon catheter and the Quick-Set Teflon catheter, starting with Quick-Set Teflon. The second group description therefore does not specify the steel set as its second device. The intended sequence for that group is not reported consistently in the registry record.
Masking is listed as none. No blinding of participants or study personnel is reported. The primary outcome is length of wear in hours, summarized with a median and interquartile range. The registry says participants with available data were analyzed. It does not report how many participants were assigned to each sequence, how the repeated device periods were analyzed, or whether any period or sequence effects were considered. The registry record also does not report a statistical analysis result for the primary comparison.
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 | Group 1: Steel Cathetar, Then Teflon | Group 2 - Teflon Cathetar, the Steel |
|---|---|---|
| STARTED | 10 | 10 |
| COMPLETED | 9 | 10 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | Group 1: Steel Cathetar, Then Teflon | Group 2 - Teflon Cathetar, the Steel |
|---|---|---|
| Withdrawal by Subject | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Participants with available data were analyzed.
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 | Group 1 - Steel Cathetar, Then Teflon | Group 2 - Teflon Cathetar, the Steel | Total |
|---|---|---|---|---|
| Participants analysed | 10 | 10 | 20 | |
| Age, Continuous | years | 22.3 (SD 8.8) | 22.3 (SD 8.8) | 22.3 (SD 8.8) |
| Gender: Female | Participants | 4 | 4 | 8 |
| Gender: Male | Participants | 6 | 6 | 12 |
| Region of Enrollment: United States | participants | 10 | 10 | 20 |
6. Primary Endpoint
The registry lists the primary outcome as Length of Wear of Infusion Site, measured over 5 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | hours |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the length of wear of the infusion site, measured in hours. It is intended to describe how long a set remains in use before wear ends. The registry's timeframe is 5 weeks, and its description says participants wore each set for up to 7 days twice. The registry also notes that infusion sets are approved for wear 2-3 days (24-72 hours), which provides context for the planned observation period.
The endpoint is summarized separately for the Sure-T Steel and Quick-Set Teflon devices. The reported statistic is the median, with an interquartile range. A median describes the middle of the observed values after ordering them. The interquartile range gives the interval from the first quartile to the third quartile, covering the central half of the observations. These summaries describe the distribution of recorded wear durations; they do not by themselves estimate a treatment contrast with uncertainty.
Wear duration is useful for this question because it directly measures the outcome named in the study objective. The registry does not specify in detail how the end of wear was defined, how an observation ending for a reason other than device failure was treated, or whether multiple wear periods were combined for each participant. Those endpoint definitions and handling rules are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary outcome gives a median wear duration of 137.0 hours for the Sure-T Steel Infusion Set Catheter, with an interquartile range from 87.0 to 168.0 hours. For the Quick-Set Teflon Catheter, the median is 145.0 hours, with an interquartile range from 99.0 to 167.0 hours. The interquartile ranges overlap. The registry does not report a confidence interval, p-value, or other inferential result for a comparison between the devices.
The outcome counts are 19 for the steel catheter and 20 for the Teflon catheter. The trial enrollment is 20. These are the numbers attached to the posted summaries; the record says participants with available data were analyzed but does not explain why the outcome counts differ. The summaries do not establish whether each count represents participants, wear periods, or another unit of analysis. That detail is not reported in the registry record.
The median is a measure of central location, while the interquartile range describes spread among the middle half of the observations. Neither summary indicates how the same participant's wear duration changed between devices. Because the study is described as crossover, a within-participant comparison could be relevant, but the posted results do not include paired differences or an analysis that accounts for the repeated periods. The summaries alone therefore do not show the precision of a device-to-device contrast.
The results are descriptive as posted. Without a reported uncertainty interval or statistical test, it is not possible to determine from the registry whether the observed summaries are compatible with a range of comparative effects, or how much uncertainty surrounds such a comparison. No conclusion about statistical significance is reported. The record's absence of an analysis result should not be mistaken for evidence that the devices are equivalent or that one has a meaningful advantage.
These figures also need to be read in light of the study's size and scope. Enrollment was 20, and the registry identifies one primary endpoint. The findings describe wear duration in this study population and under the recorded study conditions. The record does not report a basis for extending the summaries to other populations, care settings, or patterns of use. It also does not report a clinical outcome linked to the observed duration.
Although the registry lists a randomized crossover design, its account of the second sequence contains an inconsistency: the group title says Teflon then steel, while the detailed description repeats Teflon. Without a consistent sequence description and a reported analysis method, readers cannot verify how the intended crossover comparison was implemented or how sequence and period structure were reflected in the outcome summaries.
9. Statistical Methods Explained
What does the median describe?
General statistical explanation: a median is the midpoint of an ordered set of observations. It is less influenced by unusually high or low values than the arithmetic mean, which can make it useful when a distribution is skewed. In this study, the registry reports median wear durations of 137.0 hours for steel and 145.0 hours for Teflon. These are separate summaries for each intervention, not a direct estimate of the within-participant difference.
How should the interquartile range be read?
General statistical explanation: the interquartile range runs from the first quartile to the third quartile, containing the middle half of observed values. It communicates spread without requiring a normal-shaped distribution. The registry reports an interquartile range of 87.0 to 168.0 hours for steel and 99.0 to 167.0 hours for Teflon. The intervals describe variation in the recorded data. They are not confidence intervals for the difference between devices and should not be interpreted as a formal hypothesis test.
What does a crossover design imply?
General statistical explanation: a crossover design exposes a participant to more than one condition, often in a planned order. A suitable analysis may account for the fact that measurements from the same participant are related, as well as the order and period in which conditions occurred. The registry identifies this trial as randomized and crossover, and says participants wore each set for up to 7 days twice. It does not report whether the primary analysis used paired observations, how repeated periods were combined, or how period or sequence effects were handled.
The sequence details matter because the record's second group description is internally inconsistent. Its title says Teflon then steel, whereas the text says Teflon for both periods. The analysis plan and a corrected sequence description are not reported in the registry record. Consequently, the posted summaries cannot establish how the intended sequences relate to the data presented.
What information would support an inferential comparison?
General statistical explanation: an inferential comparison typically reports an effect estimate and a measure of uncertainty, such as a confidence interval, and may report a test result. A confidence interval conveys a range of values compatible with the data and the analysis assumptions. Its width reflects precision; a wider interval indicates less precision. A p-value, when reported, assesses compatibility between the data and a specified null hypothesis under the statistical model. It does not measure clinical importance or the probability that a hypothesis is true.
The registry reports zero analyses and does not post a comparison estimate, confidence interval, or p-value. It lists the primary endpoint as a median with an interquartile range, but that descriptive format is not a complete account of an analysis comparing the devices. The statistical test, model, adjustment strategy, and treatment of the crossover structure are not reported in the registry record.
Why does the distribution matter?
General statistical explanation: duration outcomes can have skewed distributions, particularly when observations are bounded by a maximum follow-up or end for different reasons. If a distribution is skewed, a mean and standard deviation may not summarize it well, while a median and interquartile range can remain interpretable. The registry's choice to report medians and interquartile ranges describes the outcome without requiring a normal-distribution assumption for those summaries. It does not reveal the complete distribution or show which statistical model, if any, was used for a formal comparison.
General statistical explanation: over-dispersion occurs when the observed variability is greater than a statistical model expects. In that situation, standard errors based on the narrower variance assumption can be too small, making uncertainty appear lower than it is. The registry record does not report an over-dispersion assessment or a model for the outcome, so no claim can be made about whether it was relevant or addressed in this study.
How should planning illustrations be understood?
General statistical explanation: sample-size calculations are planning exercises that depend on assumptions about the outcome, target effect, error rate, allocation, and analysis method. They are not measures of the probability that a completed study has detected an effect. The registry's planning description says its illustration uses the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the description says totals are events; for other outcomes, it says participants per arm.
Those assumptions describe a planning illustration, not the trial's original design justification. The registry does not report the trial's sample-size justification or identify an analysis that produced an observed comparative effect. Any sample-size illustration based on an observed effect should therefore not be read as observed power or as evidence that the completed study was adequately powered for the primary question.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies one primary outcome measure: length of wear of the infusion site. It reports no secondary outcomes. It does not report a statistical analysis plan describing how multiple tests or outcomes would be handled, and no multiplicity adjustment is reported. With no posted inferential analyses, the record does not establish whether the primary comparison was tested or whether any additional analyses were conducted outside the registry record.
The outcome description says participants with available data were analyzed. It does not define a complete analysis population, state whether participants were analyzed according to randomized sequence, or explain how observations with missing wear-duration data were handled. The outcome summaries include 19 steel observations and 20 Teflon observations, while enrollment is 20. The reason for the difference in the steel count is not reported in the registry record. Nor does the record say whether the outcome counts refer to participants or to wear periods.
In general, missing data can affect a comparison if the availability of measurements is related to the outcome or differs by condition. The direction and size of any effect depend on why data are missing and how the analysis handles them. The registry does not report the amount or reasons for missing data beyond the posted counts, or any imputation or sensitivity analysis. It is therefore not possible to assess the consequences of missingness from the posted results.
For a crossover study, missing measurements in one period can also complicate a paired analysis. The registry record does not state whether participants with an incomplete device sequence contributed to the analysis, or how incomplete sequences were treated. These analysis-population and missing-data details are 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 |
|---|---|---|---|
| Sure-T Steel Infusion Set Catheter | 0 | 20 | 0.0% |
| Quick-Set Teflon Catheter | 0 | 20 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Sure-T Steel Infusion Set Catheter | 7 of 20 |
| Quick-Set Teflon Catheter | 7 of 20 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Sure-T Steel Infusion Set Catheter | Quick-Set Teflon Catheter |
|---|---|---|---|
| Skin reaction to infusion set | Skin and subcutaneous tissue disorders | 5 of 20 | 3 of 20 |
| ketosis | Endocrine disorders | 2 of 20 | 4 of 20 |
The adverse-event record lists 20 participants at risk for serious adverse events in each device group, with 0 affected in each group. For other adverse events, it lists 20 at risk and 7 affected in each group. The record does not report deaths. These counts are presented separately by device; the registry does not explain whether participants could contribute to both groups or how events during crossover periods were assigned.
A count of participants affected is not the same as a count of event episodes. The registry reports participants affected, but does not give event-level totals, event timing, severity beyond the serious-versus-other classification, or a description of the seven other events in either group. The serious adverse event terms list is empty. No further event details are reported in the registry record.
These figures should be read as the safety information posted for this trial, not as a complete assessment of risk. The study enrolled 20 participants, and the registry does not report a formal comparison of adverse-event frequencies or uncertainty around those counts. The identical posted counts do not establish that the devices have identical safety profiles. They describe only what is recorded for this study.
12. What the Result Does, and Does Not, Mean
The result establishes that the registry reports median wear durations of 137.0 hours for the Sure-T Steel Infusion Set Catheter and 145.0 hours for the Quick-Set Teflon Catheter. It also reports the corresponding interquartile ranges and the numbers attached to each intervention summary. These are descriptive results from the completed trial's primary outcome.
The registry does not report a statistical test, confidence interval, or comparative effect estimate. Therefore, the posted summaries do not quantify how precisely the devices differ in wear duration. They do not show whether an observed contrast is compatible with no difference, or whether any difference would be important in practice. No conclusion that one device works better, or that the devices are equivalent, follows from the descriptive summaries alone.
The study is described as randomized and crossover, but the second sequence description is inconsistent and the analysis method is not posted. The record does not explain how repeated observations within participants were used. As a result, the median summaries cannot be treated as a paired estimate of the effect of changing from one device to the other.
The endpoint is duration of wear, not a direct measure of a health outcome. The registry does not report whether the length of wear was associated with other outcomes, nor does it establish that a longer duration is preferable. It also does not provide details on how wear ended or how all observations were classified. The findings should be understood within the trial's recorded endpoint, population, and study conditions, rather than as evidence about outcomes not measured in the registry.
13. Why This Trial Matters Statistically
This trial raises statistical issues that are common in device comparisons with repeated measurements. A crossover design can allow comparisons within participants, which may account for some differences between individuals. But that advantage depends on an analysis that reflects the pairing and the timing of observations. The registry identifies a crossover design without reporting how those features were handled in the primary analysis.
The study also illustrates why descriptive summaries and comparative inference are distinct. Medians and interquartile ranges show the central location and spread of the observed wear durations for each device. They do not provide a confidence interval or test for the difference between devices. Readers need the comparison estimate and its uncertainty to judge how precise the evidence is; those results are not reported in the registry record.
Accurate descriptions of treatment sequence and analysis population are especially important when each participant may use more than one device. Here, the second sequence title and detailed description do not agree. The outcome counts also differ between interventions, while the registry says participants with available data were analyzed without explaining the count difference. These gaps limit the ability to reconstruct the comparison from the posted summary.
The record is therefore informative about which endpoint was selected and what descriptive results were posted, while leaving key inferential and implementation details unreported. That distinction matters when interpreting a small crossover study: transparent reporting of sequence, repeated-measures analysis, missing-data handling, and uncertainty would be needed to understand the strength and limitations of a device comparison.
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 trial enrolled 20 participants, and the registry reports outcome counts of 19 for steel and 20 for Teflon. It does not explain the differing counts or clarify whether they refer to participants or wear periods. The record says participants with available data were analyzed, but does not provide further detail about the analysis population or missing observations.
The sequence description for the second group is inconsistent: its title indicates Teflon followed by steel, while its detailed description repeats Teflon. This prevents a clear account of the planned sequence from the registry record alone. The record does not report the numbers assigned to each sequence or whether the sequence description was corrected elsewhere.
No inferential analysis is posted for the primary endpoint. The statistical test or model, treatment of repeated measurements, handling of period or sequence effects, and uncertainty around a comparative effect are not reported in the registry record. The record also does not report a sample-size justification, a missing-data analysis, or a multiplicity plan.
The outcome description does not specify how the end of wear was defined, how premature discontinuation was handled, or how repeated observations were reduced to the summaries. The study is open label, with masking listed as none. The registry does not report whether outcome assessment was standardized or whether awareness of device type could have affected the recorded endpoint. These are limits on interpretation of the posted information, not evidence that a particular bias occurred.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Duration of Infusion Set Function: Quick-Set Teflon Catheter Versus Sure-T Steel Infusion Set Catheter — NCT01288729.
- Registry record last updated 2017-02-27; status last verified 2017-01.
- Results first posted 2017-02-27.
- 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
NCT01288729 is a completed randomized, open-label crossover study sponsored by Stanford University. It enrolled 20 participants with Diabetes Mellitus and compared the Sure-T Steel Infusion Set Catheter with the Quick-Set Teflon Catheter. The primary outcome was length of wear in hours over a timeframe of 5 weeks.
The registry reports a median of 137.0 hours for steel, with an interquartile range of 87.0 to 168.0 hours, and a median of 145.0 hours for Teflon, with an interquartile range of 99.0 to 167.0 hours. Outcome counts are 19 and 20, respectively. No comparative analysis result is posted. The registry record does not report the statistical method, a confidence interval, or a p-value, and the description of the second treatment sequence is inconsistent.