Check It! Positive Psychology Intervention to Improve Adherence in Adolescents With T1D: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Check It! Positive Psychology Intervention to Improve Adherence in Adolescents With T1D (NCT02746627), a randomized na study. The primary outcome is Glycemic Control (HbA1c).

2. Clinical Question

3. Trial Design

This was a randomized, open-label, parallel-group trial with an enrollment of 120. It was registered as completed. The registry record lists the start as 2014-01 and primary completion as 2016-02. The record identifies three groups: education, positive affect delivered by text, and positive affect delivered by phone. Because masking was listed as none, the design was not described as blinded.

The education group received educational materials by mail every 2 weeks for 8 weeks. Participants in this discussion group received weekly reminders related to gratitude, self-affirmations, parental affirmations, and gift cards by SMS, in addition to the mailed educational materials. The phone group received positive-affect reminders by telephone and small gifts by mail every 2 weeks for 8 weeks, as well as educational materials by mail every 2 weeks for 8 weeks. The arm descriptions therefore distinguish delivery mode and the listed elements of the intervention.

The registry summary describes questionnaires on mood and diabetes management at baseline, 3 months, and 6 months, with clinical measures collected from electronic medical records. The primary endpoint was HbA1c at 6 months. Other outcomes listed include frequency of blood glucose monitoring, diabetes-related quality of life, family conflict, positive affect, and coping. The registry record does not describe the randomization procedure, allocation concealment, or any stratification factors. A detailed protocol and a statistical analysis plan are not reported in the registry record, so the planned analysis procedures cannot be established from this entry.

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

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Glycemic Control (HbA1c), measured over 6 months.

The primary endpoint was glycemic control measured using HbA1c, expressed as a percentage of glycated hemoglobin. HbA1c is a clinical measure used to assess blood glucose control over time; unlike an individual blood glucose reading, it reflects a longer-term pattern. The registry record identifies the measurement as part of a diabetes clinic visit and sets the primary time point at 6 months.

The record gives the outcome as a median with interquartile range. The median describes the middle of the observed values, while the interquartile range describes the central spread of the distribution. These summaries are useful when describing an outcome without assuming that its values follow a symmetric, bell-shaped distribution. They do not by themselves estimate the difference between groups or show how uncertain that difference is.

The registry description notes a target for children and adolescents of <7.5%. This is context included in the outcome definition, not a result for any study group. The posted group medians were 8.8 for Education, 9.0 for Positive Affect - Text, and 8.5 for Positive Affect - Phone. Their reported interquartile ranges were 8.0 to 9.7, 8.3 to 9.8, and 8.0 to 9.0, respectively. The registry record does not report a formal comparison of these distributions.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry entry identifies a randomized, open-label, parallel design. Randomization is intended to make treatment groups comparable on average with respect to characteristics that could affect outcomes. In a parallel design, participants are assigned to a group and outcomes are compared across groups. These general design principles do not ensure balance in every realized trial, and they do not replace reporting the allocation procedure. The registry record does not describe how the random sequence was generated, whether allocation was concealed, or whether any randomization strata were used.

What do the posted summaries describe?

The primary endpoint is summarized with a median and interquartile range for each arm. The median is the central value when observations are ordered. The interquartile range spans the middle half of the observed distribution, so it conveys spread without being as sensitive to extreme values as the full range or standard deviation. The posted summaries are 8.8 with an interquartile range of 8.0 to 9.7 for Education; 9.0 with an interquartile range of 8.3 to 9.8 for Positive Affect - Text; and 8.5 with an interquartile range of 8.0 to 9.0 for Positive Affect - Phone.

These are within-group summaries. They are not estimates of a treatment contrast, and the interquartile range is not a confidence interval. A confidence interval, in general, expresses the uncertainty around an estimated quantity under a specified statistical method. No confidence interval for a comparison is reported in the registry record. Nor is a p-value or other inferential result reported for the primary outcome. Consequently, the posted summaries cannot show the precision of a difference between groups.

Why can the median be useful?

As a general statistical point, the median can be a suitable descriptive measure when an outcome distribution is skewed or contains unusually high or low values. The interquartile range then provides a complementary description of the central spread. Choosing a median does not, by itself, tell the reader which inferential test was planned or used. The registry record names the summary format, but a detailed statistical analysis plan is not reported.

What would an adjusted analysis add?

In general, an adjusted analysis can account for prespecified variables, such as a baseline value of the outcome, when estimating a group contrast. Such an estimate can differ from a simple comparison of group summaries. The registry record does not report a baseline-adjusted HbA1c estimate, the covariates in an adjusted model, or whether the primary comparison was adjusted. No adjustment method should therefore be assumed from the posted medians.

How should multiple groups be considered?

The registry lists an education arm and two positive-affect arms that differ by delivery mode. A statistical analysis could address an overall difference across all arms, pairwise comparisons, or a specific contrast of text with phone delivery. These are distinct questions and can call for different estimates and interpretation. The registry record does not identify a primary contrast or report an analysis for any of these comparisons. It also does not report interim analyses or a prespecified testing sequence.

Over-dispersion is a general concern when outcomes are counts, rates, or other data whose variability exceeds what a simple model assumes. A model that fails to account for over-dispersion can misstate uncertainty. The primary outcome in this record is continuous HbA1c summarized by medians and interquartile ranges, and the registry record does not describe a model for it. No claim about over-dispersion in the trial analysis is warranted. For secondary outcomes such as monitoring frequency, the outcome scale and analysis details are not reported in the registry record.

Sample-size calculations are planning tools, not evidence about the results observed in a completed trial. In general, their assumptions include the target effect, variability, significance level, allocation, and desired power. The registry record does not report the trial’s own sample-size justification or a detailed analysis plan. Any planning illustration based on an observed effect would not be an observed power calculation and would depend on assumptions distinct from the trial’s original design.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists several outcomes: the primary HbA1c endpoint and secondary outcomes concerning blood glucose monitoring frequency, diabetes-related quality of life, family conflict, positive affect, and coping. When multiple outcomes or group contrasts are tested, the chance of obtaining at least one apparently positive result by chance can increase. General approaches include identifying a primary contrast in advance, using a testing hierarchy, or adjusting for multiple comparisons. The registry record does not report a multiplicity strategy, a prespecified sequence of tests, or which contrasts were considered confirmatory.

The record lists six outcome measures and five secondary outcomes, but the inferential results and analysis details for those secondary outcomes are not reported in the registry record. It is therefore not possible to determine whether all planned outcomes were analyzed, whether any outcome was added or changed, or how the statistical interpretation accounted for multiple testing.

Missing-data handling is also not reported in the registry record. The primary outcome counts listed are 59 for Education, 29 for Positive Affect - Text, and 29 for Positive Affect - Phone, but the record does not explain whether these are all randomized participants with available HbA1c data, or how any missing values were treated. It does not state whether an imputation method, complete-case analysis, or another approach was used.

The analysis population is not defined in the registry record. It does not specify whether the reported outcomes follow an intention-to-treat principle, include only participants who completed the intervention, or use another population definition. Without those details, the relationship between randomization and the posted outcome summaries cannot be assessed fully.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry safety record lists Education with 60 participants at risk for serious adverse events and 0 affected. Positive Affect - Text lists 30 at risk and 0 affected. Positive Affect - Phone also lists 30 at risk and 0 affected. The listed counts for other adverse events are likewise 0 affected in each group, with the same respective at-risk counts.

These entries mean that the registry record reports zero participants affected in the listed serious and other adverse-event categories. They do not provide detailed event descriptions: the serious-event terms list is empty. Death counts are not reported in the registry record. Therefore, the unreported death information should not be interpreted as a recorded count of zero.

Safety counts are descriptive. They do not, by themselves, establish that the risk of an event is identical across groups or that no event occurred outside the registry’s recorded categories. The record does not provide a comparative safety analysis, event-level details, or an explanation of adverse-event collection and follow-up procedures. The figures should be read as the registry’s posted counts, not as a complete account of all possible safety information.

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

The result establishes what the registry record reports about the primary endpoint: median HbA1c at 6 months was 8.8 in Education, 9.0 in Positive Affect - Text, and 8.5 in Positive Affect - Phone, with the corresponding interquartile ranges listed for each group. These values describe the distributions of the observed outcomes. They do not alone demonstrate that one group differed from another in a statistically reliable way.

The record does not report an estimated contrast, its confidence interval, or a p-value. It also does not provide a prespecified statistical analysis plan or explain how missing outcomes were handled. As a result, it is not possible from the posted primary summaries to assess the precision of a between-group effect or determine whether the numerical differences are compatible with chance variation under a stated analysis.

The trial’s stated rationale was to test a positive psychology intervention intended to increase motivation for diabetes management, particularly blood glucose monitoring. Its stated aims also included exploring telephone and text delivery. The HbA1c summaries do not directly report whether participants found either delivery method appealing or convenient. The listed secondary outcomes cover monitoring frequency and several psychosocial measures, but secondary inferential results are not included in the registry record summarized by these registry entries.

The record includes a target of <7.5% for children and adolescents in the endpoint description. That contextual target should not be confused with a trial comparison or a conclusion about individual participants. Group-level medians and interquartile ranges do not describe every participant’s outcome, and a group summary cannot determine an individual’s clinical situation.

Accordingly, the posted information supports a descriptive reading of the three group outcomes, not a causal or clinical conclusion about the intervention. The absence of a reported comparative analysis is a limitation of what can be interpreted from the registry record; it is not evidence that an effect is absent.

13. Why This Trial Matters Statistically

This trial is statistically notable because it places two delivery modes for a behavioral intervention alongside an education comparator. Those arms represent more than a simple intervention-versus-control question: comparisons could concern the intervention as a whole, text versus phone delivery, or each positive-affect arm against education. The choice of contrast determines the question answered, so a clearly identified primary comparison matters for interpretation.

The record also illustrates why descriptive summaries should be separated from inferential claims. Medians and interquartile ranges allow a reader to understand the observed HbA1c distributions without assuming a particular model, but they do not quantify uncertainty in group differences. Reporting a prespecified contrast with an estimate and confidence interval would ordinarily help readers judge both the direction and precision of a result. Those comparative statistics are not reported in the registry record.

The behavioral components and delivery methods also make it important to distinguish intervention content from delivery. The text and phone descriptions differ in the stated use of SMS, calls, and mailed small gifts. Without a reported analysis of intervention exposure, adherence, or acceptability, the primary endpoint summaries cannot identify which component might account for any observed pattern.

Finally, the record’s limited analysis detail highlights the importance of transparent reporting of analysis populations, missing-data methods, and multiplicity handling. These details affect how randomized comparisons are interpreted, especially when several arms and outcomes are included. The posted information gives a useful outline of the trial and outcome summaries, while leaving those statistical questions unresolved.

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 interpreting the primary result is that the registry record reports arm-level medians and interquartile ranges but no inferential comparison. There is no reported effect estimate, confidence interval, or p-value for HbA1c. Thus, the magnitude and precision of any between-group difference cannot be judged from the posted summaries.

The record does not report the trial’s statistical analysis plan, sample-size justification, randomization procedure, allocation concealment, or analysis population. It also does not describe how missing HbA1c values were handled. Although outcome counts are listed by arm, the record does not explain the relation of those counts to enrollment or identify reasons for unavailable outcomes.

Several outcomes and three arms create potential multiplicity questions, but no testing hierarchy or adjustment method is reported. The registry’s descriptions of text and phone delivery include different intervention elements, and no reported adherence or acceptability analyses clarify how participants engaged with those components. The open-label design is recorded, but the record does not describe any procedures that might reduce assessment bias.

These limitations concern the information available in the registry record. They do not establish that the trial lacked procedures or analyses; those details are simply not reported in the registry record. They constrain the conclusions that can be drawn from the posted summaries.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Check It! Positive Psychology Intervention to Improve Adherence in Adolescents With T1D — NCT02746627.
• Registry record last updated 2019-03-13; status last verified 2019-02.
• Results first posted 2019-02-11.
• 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.

18. Record Summary

The registry record describes NCT02746627, a completed, randomized, open-label, parallel trial sponsored by Vanderbilt University Medical Center. It lists an enrollment of 120 and compares education with positive-affect interventions delivered by text or phone in adolescents with type 1 diabetes.

The primary endpoint was HbA1c at 6 months, reported as a median with interquartile range. The posted medians were 8.8 for Education, 9.0 for Positive Affect - Text, and 8.5 for Positive Affect - Phone. The registry record does not report a comparative statistical analysis, a sample-size justification, a statistical analysis plan, or missing-data procedures. It lists secondary outcomes related to monitoring, quality of life, family conflict, positive affect, and coping.