MOTIVATional intErviewing to Improve Self-care in Heart Failure Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for MOTIVATional intErviewing to Improve Self-care in Heart Failure Patients (NCT02894502), a randomized na study. The primary outcome is Self-care Maintenance in Patients.

2. Clinical Question

3. Trial Design

MOTIVATE-HF is recorded as a randomized, parallel, multicenter trial with single masking. It enrolled 510 participants and is marked completed. The sponsor is the University of Rome Tor Vergata. The recorded start was 2014-06, and primary completion was 2018-10. The phase is listed as not applicable.

There were three groups: motivational interviewing for patients only, motivational interviewing for patients and caregivers, and a control group receiving usual care. The outcome record reports primary endpoint data for 128.0 patients in the patient-only group, 145.0 in the patient-and-caregiver group, and 133.0 in the control group. These are the group counts attached to the posted primary outcome, rather than a description of how many participants were originally randomized or analyzed under a specified analysis population.

The primary endpoint was assessed at 3 months from the intervention. Secondary outcomes include patient symptoms, quality of life, anxiety and depression, sleep, and mutuality, as well as caregiver quality of life, anxiety and depression, sleep, mutuality, preparedness, and perceived social support. The registry lists secondary assessments at 3, 6, 9 and 12 months for burden of heart-failure symptoms.

The registry record does not report the masking procedures, allocation concealment, the precise randomization method, or the groups of people who were masked. The planned analysis population and the trial's original statistical analysis plan are not reported in the registry record. The fact that the design is randomized and parallel describes the broad comparison structure, but does not fill in those missing methods.

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.

Baseline

Reasons for not completing this period:

First Follow up

Reasons for not completing this period:

Second Follow up

Reasons for not completing this period:

Third Follow up

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 Self-care Maintenance in Patients, measured over 3 months from the intervention.

The primary endpoint is Self-Care Maintenance in patients with heart failure, measured using the Self-Care of HF Index V.6.2. The registry describes it as one of three separate scales in that instrument and identifies the Maintenance scale as the primary outcome. The scale ranges from 0 to 100, with higher values indicating better self-care. A score of at least 70 is described as adequate.

The posted endpoint is summarized as a mean and standard deviation in each group. A mean describes the group's average score, while the standard deviation describes the spread of scores around that average. These summaries address the group's average level; they do not show how many individual patients reached the adequate-score threshold. The registry record does not provide the proportion above that threshold.

Self-care is the trial's primary question because the stated study aims include evaluating motivational interviewing to improve patient self-care and caregiver contributions to self-care. The primary timepoint is 3 months from the intervention. A single primary scale and timepoint make the main comparison identifiable in the registry record, but the record does not describe how the primary endpoint was analyzed beyond the posted mean summaries and comparisons.

7. Results Posted in the Registry

• Motivational Interviewing Only for Patients: mean 52.36 versus 49.63 on control; difference 2.73 (95% CI -2.20 to 7.66), standardized effect d = 0.14; z-test p = 0.277.
• Motivational Interviewing to Patients and Caregivers: mean 54.23 versus 49.63 on control; difference 4.60 (95% CI 0.15 to 9.05), standardized effect d = 0.24; z-test p = 0.043.

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.

Burden of HF Symptoms in Patients

• 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 deviations.
• Result:
  • Motivational Interviewing Only for Patients: mean 24.00 versus 22.50 on control; difference 1.50 (95% CI -4.67 to 7.67), standardized effect d = 0.08; z-test p = 0.634.
  • Motivational Interviewing for Patients and Caregivers: mean 17.40 versus 22.50 on control; difference -5.10 (95% CI -11.35 to 1.15), standardized effect d = -0.25; z-test p = 0.110.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Motivational Interviewing Only for Patients and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Motivational Interviewing for Patients and Caregivers and the control. The interval gives the range of effects that remain compatible with the data.

The registry describes a broad set of secondary outcomes spanning patient symptoms, quality of life, emotional health, sleep and relationships with caregivers, alongside caregiver quality of life, emotional health, sleep, preparedness and social support. These domains provide context around the primary self-care question: they concern symptoms and experiences that could be related to self-care or to the involvement of a caregiver, but they are distinct outcomes and do not replace the primary endpoint.

The detailed quantitative secondary comparison in the registry record concerns burden of heart-failure symptoms, assessed at 3, 6, 9 and 12 months from the intervention. Its posted results should be considered separately from the primary Self-Care Maintenance result because it measures a different construct and uses a different outcome scale. The registry record lists 11 posted secondary outcomes, but does not report analyses for the other named secondary measures in the available outcome details.

Secondary outcomes can help describe whether the study's broader aims are reflected across different domains, but they generally carry less inferential weight when many outcomes and comparisons are examined without a reported multiplicity strategy. An unadjusted result may look more persuasive by chance when it is one among numerous tests. The registry record does not report a plan for controlling the overall false-positive rate, ranking secondary hypotheses, or distinguishing confirmatory from exploratory secondary analyses.

Accordingly, a secondary finding should not be treated as independent confirmation of the primary result or as a substitute for it. Nor should a lack of posted numerical results for a domain be interpreted as evidence of no difference. The record's incomplete analysis details mean the secondary results offer descriptive context, while their strength as confirmatory evidence cannot be determined from the registry record.

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

• Burden of HF Symptoms in Patients
• Patient and Caregiver Generic Physical and Mental Quality of Life
• Patient and Caregiver Anxiety and Depression
• Patient HF Specific Quality of Life
• Patient and Caregiver Quality of Nocturnal Sleep
• Patient and Caregiver Mutuality
• Caregiver Preparedness
• Caregiver Perceived Social Support

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: it is a numerical score on a scale, summarized by a mean and standard deviation. The posted comparisons express the difference between a motivational-interviewing group's mean and the control group's mean. A positive mean difference means the intervention-group average was higher; a negative difference would mean it was lower. Since higher Self-Care Maintenance scores indicate better self-care, the direction of the difference has that scale-specific interpretation. This is a description of the measure, not a conclusion about clinical importance.

What does a mean difference represent?

The patient-only comparison has a mean difference of 2.73 points, and the patient-and-caregiver comparison has a mean difference of 4.6 points. Each is a contrast with the same control mean, not a change from baseline and not a contrast between the two intervention groups. The registry record does not report baseline values for the primary outcome, so these estimates should not be described as within-person improvement over time.

The reported standard deviations describe variation among participants within each group. A standard deviation is not the uncertainty around the group mean: uncertainty in a mean or difference also depends on the number of observations and the variability in scores. The comparison results include confidence intervals, which express uncertainty around the estimated mean differences.

How should the p-values be read?

The p-values are labeled unadjusted. A p-value describes how incompatible the observed result is with a specified null model of no difference, under the assumptions of the analysis. It is not the probability that the null hypothesis is true, nor does it measure the size or importance of a difference. The registry record does not report the detailed test specification, such as whether the comparison used a particular variance assumption or an adjusted model. The p-values should therefore be read as the unadjusted values attached to the posted mean comparisons, not as a complete account of the trial's prespecified inferential procedure.

The p-value of 0.043 for the patient-and-caregiver comparison is below the conventional 0.05 level, while the p-value of 0.277 for the patient-only comparison is not. This distinction does not show that the intervention groups differ from each other. Comparing one p-value with another is not a test of the difference between intervention effects. The registry record does not report a direct comparison of those effects.

What does a confidence interval add?

A confidence interval gives a range of estimates compatible with the observed data and the method used to calculate the interval. Its width conveys precision: a wider interval leaves more uncertainty about the size and potentially the direction of the difference. For the patient-only comparison, the interval spans zero. For the patient-and-caregiver comparison, the lower endpoint is just above zero and the upper endpoint is 9.052. The distinction between an interval crossing zero and one ending just above zero does not remove uncertainty, and it does not establish whether the differences are clinically meaningful.

The reported standard deviations and mean differences permit descriptive comparison of the scale scores, but the registry record does not report an interpretation threshold for a clinically important between-group difference. The adequacy threshold of at least 70 is a scale classification and is not identified as a threshold for a meaningful treatment-group difference.

What remains unknown about the analysis?

The registry record does not report the original sample-size justification, interim analyses, the planned model, covariate adjustment, or an analysis population. It also does not report the handling of missing values or whether the analysis accounted for repeated observations or site. These are not details that can be reconstructed from a mean, standard deviation, and sample count. Consequently, the posted comparison can be described as an unadjusted difference based on the displayed group summaries, but its correspondence to a prespecified model cannot be established from the registry record.

The group counts attached to the primary outcome are not identical to the enrollment figure, but the registry record does not explain the relationship between enrollment, randomization, follow-up, and outcome availability. The counts alone cannot identify why participants are absent from an endpoint summary or establish the extent or pattern of missing data.

Finally, randomized assignment is part of the recorded design, but the record does not describe allocation concealment or masking procedures in detail. This prevents a fuller assessment of those design features from the registry description alone. Statistical interpretation should stay anchored to the posted summaries and explicit uncertainty rather than filling these gaps with assumptions.

11. Confidence Intervals and Precision

The confidence intervals show that the primary estimates are not highly precise. For motivational interviewing delivered to patients only, the estimated mean difference from usual care is 2.73 points, with a 95% confidence interval from -2.195 to 7.655. The interval includes zero and allows for a modest negative difference as well as a positive difference. It therefore leaves uncertainty about both direction and magnitude.

For motivational interviewing delivered to patients and caregivers, the estimated mean difference is 4.6 points, with a 95% confidence interval whose lower endpoint is just above zero and whose upper endpoint is 9.052. The interval indicates a positive unadjusted difference in this comparison, but its width leaves uncertainty about the size. It is not evidence that the true difference is exactly the point estimate.

In general, a confidence interval is a range generated by a statistical procedure that reflects sampling uncertainty under its assumptions. It does not describe the range of individual patient scores, and it does not guarantee that the true value lies in that particular interval. Here, the interval pertains to a group mean difference. The standard deviations in the groups describe individual score variability, which is a different quantity from uncertainty in the estimated contrast.

Precision is also distinct from clinical importance. The registry record specifies that a Self-Care Maintenance score of at least 70 is considered adequate, but does not state a minimum important between-group difference. The confidence intervals therefore cannot by themselves determine whether the estimated differences would be meaningful to patients or caregivers. The registry record does not report adjusted intervals or intervals for a direct comparison between intervention arms.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for comparisons between two groups, not total event counts. They are illustrations based on the observed effect, rather than the trial's original design calculation. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For each comparison, the effect to detect is set at the stated fraction of the observed effect.

The 80% power column gives the number of participants per arm that the illustration estimates would be needed for an 80% chance of detecting the specified effect under those assumptions, if that effect were the true one and the assumptions held. The 90% power column gives the corresponding per-arm number for a 90% chance. Power is a property of a planned design under assumed conditions; it is not a measure of whether a particular observed result is true or important.

Rows planning for 100%, 75%, and 50% of the observed effect describe progressively smaller target differences. Smaller effects are harder to distinguish from random variation, so the planning illustrations require more participants per arm as the target effect gets smaller. These figures do not show how many participants were actually analyzed and should not be interpreted as the trial's actual sample-size target.

This is not observed power. The original trial's sample-size assumptions and justification are not reported in the registry record. The planning figures use the displayed observed effect as an input, which makes them retrospective planning illustrations rather than evidence about the probability that the posted trial result is correct.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 2.730; pooled standard deviation σ = 20.197.
2. n = 2 × (1.96 + 0.842)² × 20.197² / 2.730² = 859.2, rounded up to 860 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 2.73                      # observed difference in means
sigma <- 20.1966952742274                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2894502)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 860 (80% power), 1,151 (90% power)
 75% of observed effect: n per arm = 1,528 (80% power), 2,045 (90% power)
 50% of observed effect: n per arm = 3,437 (80% power), 4,601 (90% power)
power.t.test: 860.1 
Simulated power at n = 860 per arm: 0.798 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The trial has a primary outcome and a substantial set of secondary outcome domains, with comparisons of each intervention group against usual care. Examining multiple outcomes and comparisons increases the chance that at least one unadjusted result will appear noteworthy even when there is no underlying difference. This is the general multiplicity problem. The registry record does not report a multiplicity adjustment, a hierarchical testing strategy, or a distinction between confirmatory and exploratory secondary outcomes.

The primary comparison for the patient-and-caregiver group has an unadjusted p-value of 0.043. Without a reported multiplicity plan, that value should not be interpreted as if it were necessarily adjusted for the other outcomes and contrasts. The registry record also does not report whether the primary outcome was the sole confirmatory test or how the two intervention-versus-control comparisons were handled in the planned analysis.

Missing-data methods are also not reported in the registry record. The primary outcome summaries include group-specific participant counts, but the record does not explain why those counts differ from enrollment, whether all randomized participants were followed, or how unavailable scores were treated. It does not report imputation, a complete-case strategy, sensitivity analyses, or assumptions about why outcome data may be missing. Without those details, the possible influence of missing outcomes cannot be assessed from the posted summaries.

The analysis population is not reported in the registry record. It is therefore unclear whether the posted estimates correspond to all randomized participants, participants with available outcome data, or another defined population. The record also does not describe protocol deviations or exclusions. These omissions do not invalidate the displayed arithmetic, but they limit assessment of whether randomization was preserved in the analysis and how robust the estimates are to missingness or analysis choices.

Interim analyses and stopping rules are not reported in the registry record. Neither the original sample-size justification nor a complete prespecified statistical analysis plan is reported. These gaps mean that the posted p-values and intervals can be interpreted as reported unadjusted comparisons, but cannot be fully evaluated against the trial's intended inferential framework.

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

The posted primary results describe average Self-Care Maintenance scores at 3 months from the intervention. The patient-only group had a higher mean than usual care by 2.73 points, but its confidence interval includes zero. The patient-and-caregiver group had a higher mean than usual care by 4.6 points, with a confidence interval beginning just above zero. These are estimates with uncertainty, not definitive statements about the experience of every participant.

The scores are measured on a scale where higher values indicate better self-care, and the registry calls scores of at least 70 adequate. Group means do not reveal the number or proportion of participants who met that threshold, nor do they describe individual changes. The registry record does not report a minimally important difference for comparing group means, so the practical importance of the estimated differences cannot be determined from these results alone.

The comparisons address each intervention group relative to usual care. They do not establish whether the patient-and-caregiver approach differs from the patient-only approach. A difference between the two intervention effects would require a direct contrast and its uncertainty, which are not reported in the registry record.

These results should not be read as proof that motivational interviewing does or does not produce a particular clinical outcome. They are posted outcome summaries from one randomized trial, with unadjusted comparisons and incomplete reporting of analysis populations, missing-data handling, and multiplicity methods. Those limitations affect the strength and scope of conclusions that can be drawn from the registry record.

The secondary outcome domains broaden the study's stated interests but do not resolve uncertainty in the primary comparison. The registry record does not provide detailed numerical analyses for all named secondary outcomes. Statistical interpretation should distinguish the stated study aims, the available outcome summaries, and questions the record leaves unanswered.

16. Why This Trial Matters Statistically

This trial raises a statistical question that is common in behavioral and caregiver-focused research: how should outcomes be interpreted when an intervention has more than one delivery format and a broad set of related outcome domains? The two motivational-interviewing groups allow separate comparisons with usual care, while the primary endpoint focuses attention on a specific patient self-care scale at a defined timepoint.

The contrast between a patient-only approach and an approach involving patients and caregivers is relevant to study design because the intervention format differs. But separate comparisons against a shared control do not themselves establish whether the formats differ from each other. A direct contrast would be needed for that question. Recognizing this distinction prevents the two control comparisons from being mistaken for a head-to-head test.

The result also illustrates why effect estimates and confidence intervals matter alongside p-values. The estimates describe the direction and size of the mean differences, while the intervals show the uncertainty that remains. An unadjusted p-value near a conventional threshold does not convey the full extent of that uncertainty, particularly in a study with multiple outcomes and comparisons.

Finally, the registry record shows how important transparent reporting is for interpretation. A randomized design is informative, but understanding the analysis also requires information about populations, missing data, multiplicity, and the prespecified plan. When those details are not reported in the registry record, readers can describe the posted comparisons while remaining appropriately cautious about their inferential reach.

17. 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 registry record leaves several trial-specific uncertainties. Although the design is listed as single-masked, it does not identify who was masked or describe the masking procedures. The method of random sequence generation and allocation concealment is not reported in the registry record. These details are relevant to understanding how participants entered the groups and how knowledge of assignment may have been managed.

The primary outcome is reported at 3 months from the intervention, while the registry lists longer follow-up timepoints for the secondary symptom-burden measure. The record does not provide a full account of follow-up completion across all arms and outcomes. The primary outcome counts differ among groups, but reasons for outcome availability and missing data are not reported in the registry record.

The record does not state whether analyses adjusted for baseline scores, center, or other variables, and it does not identify the analysis population. It also does not report a direct comparison between the two motivational-interviewing groups. Consequently, the posted estimates support description of intervention-versus-control contrasts but do not answer every comparison implied by the three-arm design.

The primary scale has an adequacy threshold, but the record posts group means and standard deviations rather than the number of participants above that threshold. A minimum important difference between group averages is not reported in the registry record. The clinical interpretation of the magnitude of the mean differences is therefore limited.

Safety fields list zero participants at risk and zero affected for serious and other events in each group, alongside death counts of 8, 7 and 13, respectively. With no further explanation of those event fields, observation periods, or ascertainment methods, these entries should not be treated as a complete comparative safety analysis.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: MOTIVATional intErviewing to Improve Self-care in Heart Failure Patients — NCT02894502.
• Registry record last updated 2021-03-17; status last verified 2021-02.
• Results first posted 2021-02-24.
• 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.

21. Record Summary

MOTIVATE-HF is a completed, randomized, parallel, multicenter trial sponsored by the University of Rome Tor Vergata, with enrollment of 510. It compares motivational interviewing delivered to patients alone or to patients and caregivers with usual care. The primary endpoint is mean Self-Care Maintenance score at 3 months from the intervention.

The patient-only comparison with usual care has a mean difference of 2.73 points and an unadjusted p-value of 0.277; the patient-and-caregiver comparison has a mean difference of 4.6 points and an unadjusted p-value of 0.043. Confidence intervals indicate uncertainty in both estimates. The registry record does not report key details of the original analysis plan, missing-data handling, analysis population, or multiplicity strategy, which limits the conclusions that can be drawn from the posted comparisons.