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 A Mixed Methods Approach to the Development and Testing of the Measure of Drug Self-Management (MeDS) (NCT01998269), a registered phase not stated study. The primary outcome is Measure of Medication Self-Management (MeDS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01998269 |
| Phase | Phase not stated |
| Condition | Diabetes, Hypertension |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 210 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of North Carolina, Chapel Hill |
| Results posted | Yes |
2. Clinical Question
Population
The record concerns adult patients with diabetes and hypertension. The official title describes intended use among English- and Spanish-speaking patients, but the enrolled participants’ language characteristics are not reported in the registry record. The registry lists enrollment of 210.
Intervention
This is an assessment-development and testing study, not a treatment trial. The Measure of Drug Self-Management (MeDS) is a medication self-management skills measure with 14 questions and a scale from 0 to 14. The record describes a cross-sectional interview lasting 1 hour after a clinic visit.
Comparator
The MeDS was compared with the Morisky Medication Adherence Scale (MMAS), described as a commonly used assessment of medication adherence. The MMAS has 8 questions and scores from 0 to 8, with lower scores reflecting better adherence. The record does not report comparative results.
Primary question
The study objective was to develop and test a measure of medication self-management for clinical use among patients with hypertension and diabetes. Statistically, the record identifies the MeDS as the primary continuous measure, but does not report its observed mean or standard deviation, or the result of its comparison with the MMAS. The record therefore does not establish how the measures related in this study.
3. Trial Design
The study is titled as a mixed methods approach to development and testing of the Measure of Drug Self-Management. Its stated objective is to develop and test an assessment for use in clinical settings among patients with hypertension and diabetes. The registry lists the study as completed, with a start date of 2013-11 and primary completion in 2014-11. Enrollment is listed as 210, and the sponsor is the University of North Carolina, Chapel Hill.
The record describes an arm of adult patients with diabetes and hypertension. It does not describe a randomized treatment comparison. Allocation is not stated, and the registry notes that the arms are not a like-for-like control comparison. Accordingly, this design should be understood as assessment development and testing rather than a trial that estimates the effect of a treatment relative to a control.
The primary measure was administered in a cross-sectional interview lasting 1 hour after a clinic visit. The record does not describe repeated measurement or follow-up for this endpoint. It identifies the MMAS as a comparator assessment, but does not report the procedures used to compare the scales. Although the title identifies a mixed methods approach, the qualitative and quantitative components, their sequence, and how they were integrated are not reported in the registry record. Recruitment procedures, eligibility details beyond the arm description, and the distribution of participant characteristics are also not reported in the registry record.
The listed enrollment is not, by itself, evidence about how many participants contributed data to the primary analysis. The analysis population and the number with complete endpoint data are not reported in the registry record. No treatment allocation, masking, or control-arm details are available that would support interpreting the study as a causal 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 | Adult Patients With Diabetes and Hypertension |
|---|---|
| STARTED | 193 |
| COMPLETED | 193 |
| NOT COMPLETED | 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 | Adult Patients With Diabetes and Hypertension |
|---|---|---|
| Participants analysed | 193 | |
| Age, Continuous | years | 61.1 (28 to 94) |
| Sex: Female, Male: Female | Participants | 116 |
| Sex: Female, Male: Male | Participants | 77 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 105 |
| Race (NIH/OMB): White | Participants | 83 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 5 |
6. Primary Endpoint
The registry lists the primary outcome as Measure of Medication Self-Management (MeDS), measured over cross-sectional, 1 hour interview after clinic visit.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the Measure of Medication Self-Management (MeDS), a continuous scale intended to assess medication self-management skills. It contains 14 questions. The stated scale ranges from a minimum score of 0, described as poor medication self-management skills, to a maximum score of 14, described as adequate medication self-management skills. The endpoint is recorded in units on a scale, and the registry identifies its summary parameter as a mean with standard deviation.
The record places the assessment in a cross-sectional interview conducted 1 hour after a clinic visit. A broad assessment of medication self-management is relevant to the study’s stated aim because the registry describes medication use as involving tasks beyond filling prescriptions and taking doses. The intended use is to assess skills in clinical settings, rather than to measure a treatment effect.
The record reports internal consistency of .72 for the scale, using Cronbach’s alpha, and describes this as adequate. Internal consistency concerns how responses across scale items relate to one another; it does not, on its own, establish that a scale measures every relevant aspect of medication management or predicts a clinical outcome. The registry also describes comparison with the MMAS, which has 8 questions and a score range from 0 to 8, with lower scores reflecting better adherence. Neither the observed MeDS mean and standard deviation nor results of the comparison are reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies the MeDS as a continuous primary measure and specifies that its results are summarized as a mean and standard deviation. However, the posted record does not provide an observed mean, standard deviation, confidence interval, or other numerical estimate for the endpoint. It also does not report a statistical test or an estimate describing the relationship between MeDS and MMAS scores. As a result, the record does not allow readers to judge the observed level of MeDS scores, their variability, or the precision of an estimate.
The stated score range gives the scale’s possible bounds, not the distribution of scores among study participants. Likewise, the description of the lowest and highest scores supplies the intended interpretation of the endpoints, but does not show where participants’ scores fell. Without outcome summaries, it is not possible to assess whether scores clustered near one end of the scale, whether there was substantial variation, or whether the measure distinguished among participants in this study.
The registry reports Cronbach’s alpha as .72 and characterizes the internal consistency as adequate. This is a reported scale property, not a substitute for the missing outcome summaries or comparative analysis. Alpha describes the consistency of item responses under particular assumptions; it does not establish agreement with another assessment, responsiveness to change, predictive validity, or clinical usefulness. Those properties require evidence suited to each question, and the registry does not report such results.
The MMAS is described as a commonly used medication-adherence assessment, but its presence as a comparator does not establish that the MeDS agreed with it or added useful information. The record does not provide a correlation, agreement statistic, group contrast, or other comparative estimate. It also does not report the direction or precision of any relationship between the scales. The two measures have different question counts, score ranges, and stated score interpretations, so raw scores should not be treated as directly interchangeable on the basis of the record.
The study’s design and reporting support a limited interpretation: it was registered as a completed measure-development and testing study with a cross-sectional assessment. The registry record does not present enough outcome information to quantify the observed performance of the MeDS in this sample. It also does not support causal claims, since the record does not describe a randomized treatment comparison and notes that allocation was not stated. No conclusion about treatment benefit or harm follows from this assessment study.
9. Statistical Methods Explained
The registry treats the primary endpoint as a continuous measure and identifies the mean and standard deviation as its summary statistics. These describe different features of a score distribution. The mean represents its central level, while the standard deviation describes how dispersed individual scores are around that mean. Neither statistic alone describes the full distribution, and a mean should be interpreted in light of the scale’s possible range and the way the scores are distributed.
What does a confidence interval express?
General statistical context: a confidence interval gives a range of values compatible with an estimate under the assumptions of the analysis. Its width reflects precision: a narrower interval indicates greater precision under that method, while a wider interval indicates greater uncertainty. The registry record does not report a confidence interval for the MeDS endpoint, so its precision cannot be assessed from the posted results.
What does Cronbach’s alpha address?
The registry reports Cronbach’s alpha of .72 and calls the scale’s internal consistency adequate. General statistical context: alpha summarizes how responses to items in a scale covary, subject to assumptions about the items and the construct being measured. It is not a general score of validity. A scale can have internally consistent items without demonstrating that it captures all relevant medication self-management skills, corresponds closely to another measure, or predicts outcomes. The registry does not report other psychometric analyses that would answer those separate questions.
How should the comparator be interpreted?
The MMAS is described as a commonly used assessment of medication adherence, and the record says that it was compared with the MeDS. This makes it a measurement comparator, not necessarily a control arm in a treatment trial. General statistical context: comparing two measures can involve examining association, agreement, or whether one measure captures information that the other does not. These are distinct questions and use different statistical summaries. The registry record does not specify the comparison method or report its result, so no particular form or strength of relationship can be inferred.
What can the planning assumptions establish?
The registry describes a sample-size planning illustration based on a stated fraction of an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It specifies that the illustration concerns participants per arm for non-time-to-event outcomes. These are planning assumptions, not evidence that the study observed a particular effect or had a particular probability of detecting it. The numerical planning outputs and the observed effect needed to interpret them are not reported in the registry record. They should not be read as observed power.
General statistical context: sample-size planning asks how much information might be needed to detect an effect of a chosen size under specified assumptions. The result depends on those assumptions, including the target effect and analysis model. A planning illustration cannot establish the precision achieved in a completed study; that requires the observed data and an analysis of them. No additional design rationale, sample-size justification, or statistical plan is reported in the registry record.
What do the design details imply for statistical interpretation?
The endpoint is described as cross-sectional and collected during an interview after a clinic visit. This identifies the measurement context but does not provide evidence about stability over time or change in response to an intervention. General statistical context: cross-sectional measurement describes scores at a particular assessment occasion; it cannot, without repeated observations or an appropriate comparison, establish change over time. The registry does not report repeated MeDS assessments.
The record does not describe random allocation and explicitly cautions that its arms are not a like-for-like control comparison. That limits interpretation of any arm contrast as a causal effect. In addition, the analysis population, handling of missing scores, and specific statistical tests are not reported in the registry record. Since the numerical endpoint results are also absent, the available information supports describing the measurement and its intended interpretation, but not estimating its observed distribution, precision, or comparative performance.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and one analysis. It does not report a multiplicity strategy, such as whether adjustments were planned for multiple hypotheses or how a primary analysis was distinguished from any exploratory analyses. The listed count alone does not establish the full set of analyses that may have been conducted, and no detailed statistical analysis plan is reported in the registry record.
The record does not state how missing MeDS responses or incomplete interviews were handled. It does not report the number of participants with endpoint data, whether any scores were excluded, how partially completed scales were treated, or whether an imputation method was used. The analysis population and the rules for inclusion in the primary analysis are not reported in the registry record. Therefore, the listed enrollment cannot be assumed to equal the number analyzed.
The registry also does not report whether missingness was assessed or whether sensitivity analyses were performed. General statistical context: missing-data methods can affect an estimate when the availability of observations is related to participant characteristics or measured outcomes. Without a report of missingness and its handling, readers cannot assess whether the endpoint summaries might be sensitive to incomplete data. This is a reporting limitation, not evidence that missing data occurred or that any particular method was used.
Numerical primary endpoint results are not reported in the registry record, so it is not possible to assess how uncertainty was quantified or whether any multiplicity adjustment affected an estimate. No assumptions about the analysis population or missing-data procedure should be made from the record’s enrollment figure or its completed status.
11. What the Result Does, and Does Not, Mean
The record establishes the study’s aim: to develop and test a medication self-management assessment for clinical settings among patients with hypertension and diabetes. It describes the MeDS as a 14-question scale scored from 0 to 14 and reports Cronbach’s alpha of .72, which it characterizes as adequate internal consistency. It also states that the MeDS was compared with the MMAS.
Those descriptions do not show how participants scored. The registry does not report the observed mean or standard deviation for the MeDS, or a result quantifying its relationship with the MMAS. It therefore cannot establish from the posted results how much variation in scores was observed, how precisely the scale’s average was estimated, or whether scores on the two assessments were associated or in agreement. The scale’s stated score bounds and alpha value do not fill in those missing results.
The record also does not establish that the assessment improves clinical decisions, predicts health outcomes, or changes medication use. Those claims require evidence beyond a description of a scale and its internal consistency. Nor does the study provide evidence about a treatment effect: it is an assessment-development study, and the registry does not describe a randomized treatment comparison.
The appropriate conclusion is narrow. The registry documents the scale’s stated structure, intended population, assessment setting, and reported internal consistency, while leaving the primary endpoint results and comparative findings unavailable. The record’s status is completed, but completion status is not itself evidence that the measure met a particular performance criterion. Readers should distinguish these reported design and scale details from outcome evidence that is not reported in the registry record.
12. Why This Trial Matters Statistically
Medication self-management is broader than taking doses alone, according to the study rationale. The study’s statistical focus is therefore measurement: how to represent a set of skills in a scale intended for use in clinical settings. This raises questions that differ from those in a treatment trial, including whether the items cohere, whether the scale captures relevant tasks, and how its scores relate to other assessments.
The registry gives a concrete description of the proposed measure: 14 questions, a score range from 0 to 14, and reported internal consistency of .72. These details help define what is being measured and how the scale was characterized. The planned comparison with the MMAS also reflects a measurement question rather than a treatment contrast. Keeping that distinction clear helps prevent an assessment study from being interpreted as evidence about the effectiveness of a clinical intervention.
The record also illustrates why reporting numerical results matters. A scale’s design and an internal-consistency statistic do not show the observed score distribution, the precision of an average, or how the scale performed relative to another measure. Those results are not reported in the registry record. Without them, readers cannot evaluate the empirical performance of the MeDS in this study, even though its objective and basic scoring structure are described.
For biostatisticians and clinical researchers, the central statistical lesson is that measurement claims require evidence matched to the claim. Internal consistency, agreement, association, validity, and clinical usefulness are not interchangeable properties. A report should identify the analysis used for each question and provide estimates with appropriate uncertainty. The available registry information makes the measurement objective clear, but leaves the principal outcome and comparative evidence unavailable.
13. 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 statistical interpretation is that the registry does not report numerical results for the primary endpoint. The observed MeDS mean and standard deviation, estimates of uncertainty, and comparative findings for the MMAS are not reported in the registry record. As a result, readers cannot evaluate the observed score distribution or the precision and magnitude of any reported relationship.
The registry’s design description is limited. Although the title identifies a mixed methods approach, details of the qualitative and quantitative methods, their integration, and the analysis procedures are not reported in the registry record. The record identifies a cross-sectional interview 1 hour after a clinic visit but does not describe repeat assessments. It therefore does not provide evidence about test-retest reliability or responsiveness to change.
Participant characteristics beyond the adult diabetes and hypertension arm description are not reported in the registry record. The official title refers to English- and Spanish-speaking patients, but the language distribution of enrolled participants is not reported. The record does not provide eligibility details, recruitment information, or the analysis population. Although enrollment is listed as 210, the number contributing complete primary endpoint data is not reported.
The record reports internal consistency of .72, but does not report other measurement properties or the method used to compare the MeDS with the MMAS. Allocation is not stated, and the registry notes that the arms are not a like-for-like control comparison. Missing-data methods, multiplicity handling, and a detailed statistical analysis plan are also not reported. These gaps constrain interpretation of the measure’s performance and do not permit causal conclusions.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: A Mixed Methods Approach to the Development and Testing of the Measure of Drug Self-Management (MeDS) — NCT01998269.
- Registry record last updated 2015-04-02; status last verified 2014-11.
- Results first posted 2015-04-02.
- 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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17. Record Summary
NCT01998269 is a completed study sponsored by the University of North Carolina, Chapel Hill, with enrollment listed as 210. Its title describes a mixed methods approach to developing and testing the Measure of Drug Self-Management for clinical use among patients with hypertension and diabetes.
The primary outcome is a continuous MeDS score, summarized as a mean and standard deviation. The scale has 14 questions and ranges from 0 to 14. The registry reports Cronbach’s alpha of .72 and describes internal consistency as adequate. The assessment was administered in a cross-sectional interview 1 hour after a clinic visit. The MeDS was compared with the MMAS, described as a commonly used medication-adherence assessment.
The registry does not report the primary endpoint’s observed mean or standard deviation, the comparative results, or the analysis population. Allocation and detailed statistical methods are not reported in the registry record.