Tailored Approaches to Improve Medication Adherence: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Tailored Approaches to Improve Medication Adherence (NCT01643473), a randomized na study. The primary outcome is Feasibility of Retaining Study Participants Through the 3 Month Trial.

2. Clinical Question

This question is about feasibility: whether participants could be followed from baseline to the 3-month assessment. Retention matters because missing follow-up can limit the amount of information available for evaluating an intervention and can affect how representative the observed results are of the enrolled group. The registry also lists changes in blood pressure, HbA1c, and self-reported medication adherence as secondary outcomes. Those outcomes address different questions from retention and should be read as secondary evidence, not as substitutes for the primary feasibility measure.

3. Trial Design

The registry describes a randomized study with single masking and a planned enrollment of 42. It lists an attention control and a tailored adherence intervention. The tailored intervention was delivered on a tablet and matched to participants’ most salient adherence barriers; the control used health education videos unrelated to medication adherence, hypertension, or type 2 diabetes.

There is an internal design-description ambiguity in the registry: the allocation is listed as randomized, while the study model is listed as single group. At the same time, the record describes two interventions and posts results for two arms. The registry does not clarify this combination, so the design structure should not be inferred beyond those recorded details. The masking entry is single, but who was masked is not reported in the registry record.

The study started in 2013-04, had primary completion on 2018-02-20, and is listed as completed. The primary assessment concerned retention through 3 months. Secondary outcomes include changes from baseline in systolic and diastolic blood pressure, HbA1c, and self-reported medication adherence at 3 months. Although the registry lists these secondary outcomes, numeric results are posted for HbA1c and medication adherence; results for the blood-pressure outcome are not reported in the registry record.

The outcome arm counts are 20 for attention control and 21 for the tailored intervention. These posted counts do not account for the full enrollment figure in the same way, and the registry does not report an explanation for the difference. The number assigned to each arm, the sequence-generation method, concealment procedures, and the details of follow-up procedures 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The number of participants that were retained in the study from baseline to 3 months.

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 Feasibility of Retaining Study Participants Through the 3 Month Trial, measured over 3 months.

The primary endpoint is the absolute number of participants retained from baseline through 3 months. The registry defines feasibility in terms of how many patients remained in the study after consenting and enrolling at baseline. This is a count outcome: it records participants, not the percentage retained, the amount of medication taken, or a change in health status.

Retention is useful in a feasibility study because continued participation determines whether follow-up measurements can be collected. If participants do not complete follow-up, later outcome data may be unavailable, and the remaining observations may not fully represent everyone who enrolled. Retention therefore describes an important part of whether the study procedures can sustain participation over the stated follow-up period.

The posted primary results give a retained count of 20 in attention control and 21 in the tailored intervention arm. The registry’s comparison reports a risk difference of 0.0, with limits of 0.0 and 0.0. The count values equal the corresponding posted outcome arm sizes. This result describes observed retention in the listed groups; it does not, by itself, establish whether the intervention is acceptable, whether medication adherence changed, or whether blood pressure or HbA1c changed.

The registry does not report a separate acceptability measure among the posted primary outcomes. Nor does the count reveal why participants were retained or not retained. Those details, including any reasons for missed assessments, are not reported in the registry record.

7. Results Posted in the Registry

• Tailored Adherence Intervention: 100.0% (21/21) versus 100.0% (20/20) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0), risk ratio 1.00 (1.00–1.00); unadjusted two-proportion z-test p = n/a.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Change From Baseline in HbA1c at 3 Months

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Tailored Adherence Intervention: mean -0.50 versus 0.60 on control; difference -1.10 (95% CI -2.23 to 0.03), standardized effect d = -0.60; z-test p = 0.056.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Tailored Adherence Intervention and the control. The interval gives the range of effects that remain compatible with the data.

Change From Baseline in Self-reported Medication Adherence at 3 Months

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Tailored Adherence Intervention: mean 1.30 versus 1.80 on control; difference -0.50 (95% CI -1.84 to 0.84), standardized effect d = -0.23; z-test p = 0.466.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Tailored Adherence Intervention and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes address several distinct domains: blood pressure, HbA1c, and self-reported medication adherence. Taken together, the numerical results that are posted do not present a consistently precise pattern of between-group differences. The registry does not post numeric results for blood pressure, so the overall pattern cannot be assessed across every listed secondary outcome. The results available for the other outcomes should be viewed as exploratory evidence rather than a complete account of the study’s secondary findings.

These outcomes are related to the intervention’s stated focus on medication adherence and to the conditions described in the study summary, but they are not the same as the primary retention outcome. Retention tells whether participants remained under follow-up; it does not establish that adherence changed. Similarly, changes in HbA1c or blood pressure would be clinical measurements, whereas the self-reported adherence measure is a participant-reported score. Each outcome has its own meaning, measurement properties, and potential sources of error.

Unadjusted secondary results carry less weight when several outcomes are examined because repeated testing can make chance patterns more likely. The registry does not report a multiplicity plan, a prespecified hierarchy for secondary outcomes, or a documented analysis plan. It also lists no reported analyses for the secondary outcomes. Without those details, the secondary estimates and p-values cannot be treated as a fully documented confirmatory analysis.

The primary retention result offers a direct descriptive account of follow-up in the listed arms, while the secondary outcomes suggest questions for further evaluation. The absent numeric blood-pressure results and missing analysis details prevent a comprehensive comparison across all listed secondary measures. The secondary findings therefore complement the feasibility result but do not strengthen it into a broad conclusion about clinical or adherence effects.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Change From Baseline in Mean Systolic and Diastolic Blood Pressure at 3 Months
• Change From Baseline in HbA1c at 3 Months
• Change From Baseline in Self-reported Medication Adherence at 3 Months

9. Statistical Interpretation

10. Statistical Methods Explained

Several statistical ideas help clarify what the posted estimates do and do not say. The registry presents a count for retention and mean changes for two secondary outcomes. These outcome types summarize different quantities and should not be interpreted as interchangeable evidence. The specific statistical analysis plan is not reported in the registry record.

What does a count outcome represent?

A count records how many participants met an outcome definition. For retention, the definition is being retained in the study from baseline to 3 months. A count is distinct from a rate or proportion because it does not, on its own, state the count relative to the number eligible or enrolled. In this record, the comparison is expressed as a risk difference, which is a difference between the proportions in the two groups. The posted comparison is 0.0, and its reported limits are both 0.0.

In general, a risk difference describes the absolute separation between group proportions. It is often straightforward to interpret, but its meaning depends on a clear definition of the outcome and of each group’s denominator. The registry gives outcome arm sizes and retained counts, but it does not explain the zero-width interval. A reported interval with identical limits should not be taken as proof that the true population difference is known exactly. It describes the interval as posted, not the full uncertainty that might be relevant to another study or population.

How should mean differences be read?

A mean difference subtracts one group’s mean from the other group’s mean according to the stated comparison. Its sign indicates which group’s reported mean is numerically higher, given that comparison’s ordering. The HbA1c comparison is -1.1, and the medication-adherence comparison is -0.5. Each estimate is accompanied by a confidence interval. When an interval includes zero, values consistent with no average difference remain compatible with the interval, as do values on either side of zero. This does not prove there is no effect; it indicates that the estimate is not precise enough to distinguish the possible values captured by that interval.

The registry reports standard errors alongside the group means. A standard error describes uncertainty in an estimated mean, rather than variation among individual participants. It should not be read as the range of individual outcomes. The record does not describe how these standard errors were obtained or whether they reflect an adjusted model. Its statistical plan and details of any covariate adjustment are not reported in the registry record.

What is the role of a p-value?

A p-value assesses how compatible observed data are with a specified null hypothesis under the assumptions of the statistical test. It is not the probability that the null hypothesis is true, and it does not quantify the size or practical importance of a difference. The posted secondary p-values are labelled unadjusted. They should be interpreted with the effect estimates and confidence intervals, rather than on their own. The registry does not report a p-value for the primary retention comparison.

Because the secondary results are unadjusted and multiple outcomes are listed, chance findings are a consideration. The registry does not report whether a multiplicity strategy was planned or whether any outcomes were designated for confirmatory testing. The p-values therefore do not establish a controlled overall error rate across the secondary outcomes.

What do planning illustrations mean?

The sample-size illustrations are calculated from the observed effects and are described as planning illustrations, not as the study’s design calculations. They assume a two-sided significance level of 0.05, equal allocation, and a normal approximation. Their rows consider planning for 100%, 75%, and 50% of the observed effect, with separate targets for 80% and 90% power. The required participants per arm increase as the assumed effect becomes smaller. These figures are not observed power, do not show what power the completed study had, and do not establish the rationale for the original enrollment.

In general, a planning calculation asks how many participants a future study might require under stated assumptions. Its answer depends on the effect size, variability, allocation, statistical test, and other design choices. Here, those calculations are based on observed effects rather than a reported protocol target. The original sample-size justification is not reported in the registry record.

11. Confidence Intervals and Precision

A confidence interval expresses a range of effect values compatible with the observed data under the method used to construct it. It conveys uncertainty around an estimate; it is not a guarantee that the true value lies within the interval, nor does its width alone tell whether an effect matters clinically. The registry does not report the confidence level or the method used to construct the secondary intervals.

For HbA1c, the mean difference is -1.1 and the interval extends from -2.226 to 0.026. For self-reported medication adherence, the mean difference is -0.5 and the interval extends from -1.844 to 0.844. Both intervals include zero, so the posted estimates are compatible with no mean difference as well as with differences in either direction. Their spans indicate substantial uncertainty relative to the point estimates. The results do not precisely establish a single effect size.

The primary retention comparison is reported with a risk difference of 0.0 and interval limits of 0.0 and 0.0. That interval has no displayed width. It should be read as the registry’s posted interval, not as evidence that there is no uncertainty about retention in a broader population. The method and assumptions behind this interval are not reported in the registry record, so its apparent precision cannot be assessed from the record alone.

Small group sizes also limit how much information these results can provide, especially for secondary outcomes. A point estimate is only one summary of the data; its uncertainty and the design and analysis details matter. The planning illustrations reinforce that future sample-size requirements depend strongly on the effect assumed. They are hypothetical design calculations based on observed effects and do not make the present estimates more precise.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcomes, including retention, blood pressure, HbA1c, and self-reported medication adherence. When several outcomes are examined, the chance of finding an apparently unusual result by chance can increase. Statistical approaches such as adjusting significance thresholds, specifying a testing hierarchy, or identifying a limited set of confirmatory outcomes can address this issue. These are general methods; the registry does not report which, if any, were planned for this study.

The posted secondary p-values are unadjusted. No multiplicity adjustment or prespecified ordering is reported in the registry record. The results should therefore not be read as if they were part of a documented family of tests with controlled overall error. The record lists no reported analyses for the secondary outcomes, and it does not provide enough detail to determine whether the posted comparisons were planned before the data were examined.

Missing-data handling is another important issue. The primary outcome counts participants retained through 3 months, but the registry does not report reasons for loss to follow-up, the amount or pattern of missing secondary measurements, or how missing values were handled. It does not state whether the secondary analyses used complete cases, imputation, or another approach. Those details are not reported in the registry record.

The analysis population is also not described. The record does not say whether participants were analyzed according to randomized assignment, whether any participants were excluded from outcome analyses, or how deviations from assigned intervention were handled. The distinction matters because analyses based on different participant sets can estimate different quantities. The reported enrollment is 42, while the primary outcome arms list 20 and 21 participants; an explanation of how those figures relate is not reported in the registry record.

These omissions do not invalidate the posted counts or estimates, but they limit assessment of bias and inferential strength. A fuller interpretation would require the prespecified analysis plan, participant flow, missing-data information, and clarification of the analysis populations. None is reported in the registry record.

13. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry’s adverse-event figures report zero serious adverse events and zero deaths in both groups. For both serious and other adverse events, the listed number at risk is 21 in attention control and 21 in the tailored adherence intervention arm. These are descriptive counts for the recorded safety outcomes.

A count of zero reported events means no events were recorded in the listed category and group; it does not establish that the risk is absent. The figures depend on the number followed, the period and procedures for collecting events, and how events were classified. The registry does not provide further detail about safety-monitoring procedures, event definitions, or the period covered by the adverse-event counts. Those details are not reported in the registry record.

The safety counts should also be kept distinct from the primary retention outcome and the secondary efficacy-related measures. They do not indicate whether participants completed follow-up or whether adherence or clinical measures changed. The posted figures are limited to the recorded event counts and should not be generalized beyond the study information available.

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

The primary result describes retention through 3 months in the two groups listed in the registry. The recorded counts are 20 for attention control and 21 for the tailored adherence intervention, and the posted risk difference is 0.0. This is a description of the observed follow-up counts; it is not, by itself, proof that retention would be identical in another sample or setting.

The study was intended to culturally tailor a technology-based adherence intervention for Black and Latino patients described as having uncontrolled hypertension or type 2 diabetes and not adhering to medication, and to determine acceptability. The posted primary outcome addresses retention, not acceptability directly. The registry does not report a separate quantitative acceptability result among the posted outcomes, so the retention figures alone cannot answer the full stated purpose.

The secondary measures provide additional but uncertain information. The HbA1c and self-reported adherence estimates have intervals that include zero, and no numerical blood-pressure result is reported in the registry record. These data do not establish a clear between-group difference in those reported secondary comparisons. They also should not be treated as evidence that there is no difference; the estimates are imprecise and the analysis details are limited.

Nothing in these results establishes a treatment effect for a broader patient population. The number of participants is limited, and the record does not report the analysis population, missing-data handling, or detailed statistical plan. The ambiguous combination of a randomized allocation entry and a single-group model entry further limits certainty about the study structure. The results support a cautious reading of the recorded counts and estimates, not a clinical recommendation.

15. Why This Trial Matters Statistically

This trial is statistically informative because it separates feasibility from outcome change. Retention is a practical condition for obtaining follow-up data, but it is not the same as adherence, acceptability, or clinical benefit. Keeping those questions distinct prevents a favorable-looking count from being interpreted as evidence about outcomes it did not measure.

The record also illustrates why effect estimates and uncertainty should be considered together. The secondary mean differences are accompanied by intervals that include zero, so their point estimates alone do not tell a decisive story. A p-value is not a measure of effect size, and unadjusted p-values across several outcomes have to be interpreted cautiously. The registry’s lack of a documented multiplicity strategy makes that caution especially relevant.

Another statistical lesson is that a planning calculation based on an observed effect is not the same as a prospective sample-size justification. The posted illustrations show how assumed effect size affects the participants per arm required under stated assumptions. They do not reveal the rationale for the actual enrollment or the study’s achieved power.

Finally, reporting details are part of statistical interpretation. The record gives outcome counts and selected summary statistics, yet leaves the analysis population, missing-data methods, analysis plan, and some outcome results unreported. It also pairs a randomized allocation entry with a single-group model entry. These reporting gaps do not change the displayed values, but they constrain the claims that can responsibly be made from them.

16. 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 record affect interpretation. The registry lists randomized allocation but also identifies the model as single group, while describing two intervention arms and reporting two-arm results. The record does not clarify this inconsistency. The masking entry is single, but the identity of the masked parties is not reported in the registry record.

The reported enrollment is 42, while the primary outcome groups list 20 and 21 participants. The relationship between enrollment and the outcome arm counts is not explained. The reason for any difference, if applicable, is not reported in the registry record. Likewise, the adverse-event counts use 21 participants at risk in each group, which does not match the primary outcome arm counts in the same way; the record does not explain this.

The primary count is a limited feasibility measure. It does not directly quantify acceptability, adherence, or clinical outcomes. The registry does not provide reasons for retention or non-retention, and it does not report detailed participant flow or missing-data handling. These omissions make it difficult to assess whether the observed follow-up counts could conceal differences in who contributed data.

Numeric results are available for two secondary outcomes, but not for the listed blood-pressure outcome. The statistical analysis plan, multiplicity handling, and analysis populations are not reported in the registry record. The secondary comparisons are therefore difficult to place in a prespecified inferential framework. The sample-size illustrations are based on observed effects and are not the trial’s reported design justification. Each limitation narrows the conclusions that can be drawn from the posted results.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Tailored Approaches to Improve Medication Adherence — NCT01643473.
• Registry record last updated 2019-09-26; status last verified 2019-09.
• Results first posted 2019-09-26.
• 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.

20. Record Summary

NCT01643473, Tailored Approaches to Improve Medication Adherence, is listed as completed and as randomized, with single masking and a single-group model entry. The registry describes an attention control using unrelated health education videos and a tablet-based tailored adherence intervention. Enrollment was 42, and the primary follow-up period was 3 months.

The primary outcome is the number retained from baseline to 3 months. The posted counts are 20 in attention control and 21 in the tailored intervention arm, with a reported risk difference of 0.0 and interval limits of 0.0 and 0.0. Secondary results are posted for HbA1c and self-reported adherence; numeric blood-pressure results are not reported in the registry record.

Interpretation is limited by unreported analysis and missing-data details, absent multiplicity information, and an unresolved design-description ambiguity. The posted data describe retention and uncertain secondary estimates; they do not resolve the study’s full acceptability question or establish broader intervention effects.