The Efficacy of Individualized Dietary Advice in Improving Diet Quality and Cardiovascular Health: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Efficacy of Individualized Dietary Advice in Improving Diet Quality and Cardiovascular Health (NCT03854461), a randomized na study. The primary outcome is Difference in Mean Change in Prime Diet Quality Score Between Groups Between Months 0 and 6.

2. Clinical Question

This is a question about a between-group difference in change, not simply whether one group changed from its own starting value. The comparison is designed to distinguish the change associated with the personalized-advice approach from change in the group receiving educational material. The record describes a six-month dietary intervention and identifies diet quality and cardiometabolic outcomes as its broad aims. It does not report whether the primary measure differed between groups, how large any difference was, or how precisely it was estimated. It also does not report a threshold for a change that would be considered important to participants or researchers. Consequently, the registry record allows the question and its measurement to be described, but not answered from outcome estimates.

3. Trial Design

The study is described as a randomized, parallel-group dietary intervention lasting six months. It enrolled 162 participants and is marked completed in the registry record. The study start is listed as 2022-01-01, and primary completion as 2024-03-31. The phase is listed as not applicable. The sponsor is Queen's University, Belfast.

One group received personalized dietary advice and educational material; the comparison group received educational material. The intervention descriptions indicate that the personalized approach used individualized recommendations incorporating food markers of diet quality. The comparator material was intended to encourage dietary change towards a better-quality diet. The registry record does not describe the allocation procedure beyond identifying the study as randomized. It identifies masking as single, but does not report who was masked or how masking was maintained.

The brief study description characterizes participants as being at high risk of cardiovascular disease and living in Ireland, North and South. It does not report the criteria used to define risk, detailed eligibility requirements, or further participant characteristics. The primary outcome was assessed by questionnaire. The record notes that, at Month 6, some participants completed the questionnaire, including the primary outcome, without completing visits for secondary outcomes; some completed visits for secondary outcomes without completing the questionnaire for the primary outcome. This indicates that outcome availability could differ across measures, but the record does not give the number of participants with each type of completion.

The listed secondary outcomes include alcohol consumption, medication use, physical activity, anthropometric measures, body composition, and blood pressure. The record lists 12 outcome measures overall, but does not report results for them in the registry record. It also does not report the intended sample-size justification, detailed analysis plan, or specific statistical tests.

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.

Before assignment: As n=12 participants who were enrolled onto the study were not contactable afterwards to arrange baseline (Month 0) study visits, n=162 participants in total were enrolled to account for losses identified early in data collection process before baseline visit. N=150 completed baseline (Month 0) visits but n=1 participant was discovered to be ineligible at baseline visit and was removed. Therefore n=149 completed baseline visits and were randomised.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Primary outcome was assessed via questionnaire. At Month 6 some participants completed questionnaire only (including primary outcome) but not visits (secondary outcomes; whilst some participants completed visits only (secondary outcomes) but not questionnaires (primary outcome).

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.

Population: N=1 participant was deemed ineligible at baseline study visit and was removed-they had withheld relevant information at screening.

6. Primary Endpoint

The registry lists the primary outcome as Difference in Mean Change in Prime Diet Quality Score Between Groups Between Months 0 and 6, measured over Baseline and six months.

The primary endpoint is the difference between groups in mean change in Prime Diet Quality Score (PDQS) between baseline and six months. The PDQS is an overall score derived from reported food consumption. The registry description classifies food groups as healthy or unhealthy, awards points for consumption of healthy groups, and reverses scoring for unhealthy groups. Points across 21 food groups are summed. The total score ranges from 0 to 42, with a higher score indicating better diet quality.

The endpoint is intended to capture diet quality as a combined measure rather than focus on a single food or nutrient. A change score expresses how the measure differs between baseline and follow-up; comparing mean change between randomized groups addresses whether their average changes differed over the same period. The endpoint is assessed by questionnaire, specifically an online version of the PDQS. The record does not report questionnaire completion counts or the primary outcome values.

The registry lists the outcome as a mean and identifies a 95% confidence interval as its dispersion measure. A confidence interval describes uncertainty around an estimate under the analysis used; it is not itself a measure of clinical importance. Neither the between-group estimate nor its confidence interval is reported in the registry record. The record also does not state what size of PDQS change would be meaningful, so the scale’s direction and range can be described, but the importance of a particular change cannot be judged from this entry.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean change compare?

For a continuous measure such as PDQS, a mean summarizes the average score in a group. A change score compares a participant’s follow-up measurement with that participant’s baseline measurement. The primary question then compares the average change between the randomized groups. This differs from comparing follow-up values alone or asking whether either group changed from baseline. Those approaches address different statistical questions. The registry identifies the intended endpoint as a difference in mean change, but does not report the analysis details used to estimate it.

How should a confidence interval be read?

The registry lists a 95% confidence interval as the measure of dispersion for the primary endpoint. In general, a confidence interval communicates uncertainty around an estimated effect. It helps readers assess which effect sizes are compatible with the observed data under the statistical method used. It should be interpreted together with the estimate, the outcome scale, and the study question. It is not a guarantee that the true value lies within the particular interval, nor does it by itself determine whether an effect matters in practice. The interval and estimate are not reported in the registry record, so their implications cannot be assessed for this trial.

What does randomization contribute?

In general, random allocation is intended to make comparison groups similar, on average, with respect to characteristics measured and unmeasured before intervention. This supports interpretation of a between-group comparison, subject to how allocation was carried out, follow-up, outcome measurement, and analysis. The registry labels the trial randomized and parallel-group. It does not describe the sequence-generation method, allocation concealment, or allocation ratio. Those details are not reported in the registry record, so the label alone does not establish how each design feature was implemented.

What is known about the statistical plan?

The registry identifies a mean as the primary outcome parameter and a 95% confidence interval as its dispersion measure. It does not report a specific model, test, adjustment strategy, handling of baseline scores, or analysis population. These choices can affect an estimate and its uncertainty. For example, a model may account for baseline outcome values or other prespecified factors, but whether this study did so is not reported in the registry record. The appropriate interpretation is to distinguish the stated outcome summary from the unreported analysis procedure rather than infer a method from the endpoint description.

What do planning illustrations represent?

General sample-size planning asks how much information might be needed to detect an effect under chosen assumptions. The registry’s planning description identifies a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation; it says the effect to detect is a stated fraction of the observed effect. It also states that these are planning illustrations computed from the observed effect, not the trial’s own design. They should therefore not be described as the trial’s prespecified sample-size justification or as observed power. The registry record does not report that justification. A planning illustration is conditional on its assumptions and does not establish whether an actual study result is precise or important.

Why can missingness matter?

The record says that some participants completed the Month 6 questionnaire but not the visits for secondary outcomes, while some completed secondary-outcome visits but not the primary-outcome questionnaire. In general, outcome-specific missingness matters because the number and characteristics of participants contributing data can vary across outcomes. Statistical handling of missing data depends on the pattern and reasons for missingness and on the assumptions used. The record does not report the number missing for the primary endpoint, reasons for missing questionnaires, or the method used to handle missing data. No particular missing-data assumption or method can therefore be attributed to this study.

Finally, the registry lists 12 outcome measures and zero analyses. This indicates that statistical analysis results are not listed in the registry record, not that no analyses were conducted. A complete statistical interpretation would ordinarily need the estimate, uncertainty, analysis population, and analysis method, alongside a clear account of missing data and any prespecified comparisons. Those details are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures. The primary endpoint is identified as the difference in mean change in PDQS between baseline and six months. Other listed outcomes include alcohol consumption, medication use, physical activity, anthropometric measures, body composition, and blood pressure. The record does not explain which secondary outcomes were confirmatory, how comparisons were prioritized, or whether any adjustment for multiple testing was planned. Multiplicity methods and their use are not reported in the registry record.

In general, evaluating many outcomes or comparisons can increase the chance of findings that appear noteworthy by chance. Adjustment procedures and prespecified hierarchies can address this issue, but their suitability depends on the questions and analysis plan. No such approach should be assumed for this trial from the list of outcomes alone. The registry lists zero analyses, so it does not provide posted analysis results or clarify how the primary and secondary outcomes were evaluated.

The record notes differing Month 6 completion patterns: some participants completed the primary-outcome questionnaire without secondary-outcome visits, while others completed visits without the primary questionnaire. It does not report the number with missing primary data, reasons for noncompletion, or the method used to address missing observations. The analysis population, including whether all randomized participants were included in the primary analysis, is not reported in the registry record. Consequently, outcome-specific denominators and the potential influence of missing data cannot be assessed from this entry.

11. 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 2% reporting threshold.

The registry lists serious adverse events for 0 of 75 participants at risk in the personalized dietary advice and educational material group, and 0 of 74 in the educational material group. It also lists other adverse events for 0 of 75 and 0 of 74, respectively. Deaths are listed as 0 in both groups, and no serious adverse-event terms are listed.

These entries describe the counts recorded in the registry; they do not estimate comparative risk or establish that no unrecorded events occurred. They also do not show whether all participants were observed for the same duration or whether adverse-event collection was complete. The record does not provide additional detail about event definitions, monitoring procedures, severity beyond the serious-event classification, or attribution to an intervention. The adverse-event denominators should not be read as the number who completed the primary-outcome questionnaire, because the record describes different completion patterns across questionnaires and visits. These safety figures are registry counts and do not provide a basis for medical advice.

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

The registry record describes a randomized parallel-group comparison of personalized dietary advice plus educational material against educational material, with diet quality assessed at baseline and six months. The primary endpoint uses the PDQS, an overall dietary-quality score for which higher scores indicate better diet quality. These details identify the scientific question and the intended outcome measure.

However, the registry record does not report the primary outcome estimate, group changes, confidence interval, p-value, or analysis method. It therefore cannot show whether the groups differed, in which direction, by how much, or with what precision. The completion status of the study does not fill this reporting gap. Without the estimate and uncertainty, readers cannot determine how compatible the observed data are with different possible between-group effects.

The score’s range and direction help interpret a result if one is available, but do not establish the importance of any particular change. The record does not identify a threshold for a meaningful difference. It also does not report how many participants contributed primary-outcome data or how missing questionnaires were handled. Those omissions limit assessment of the result’s robustness and applicability.

The record’s safety counts list no serious or other adverse events and no deaths in the reported groups, but these counts should be read as registry entries, not as proof that events could not occur or were comprehensively captured. In sum, this record can support a description of the trial design and outcome definition. It cannot support a conclusion about the efficacy of the dietary advice or the size and precision of a primary-outcome effect.

13. Why This Trial Matters Statistically

This trial addresses a statistical question that is distinct from whether people in either group changed their diets over time: whether mean change in diet quality differed between randomized groups. A between-group change contrast is the relevant form of comparison for the stated primary question. The registry specifies this contrast and identifies the PDQS as its measurement instrument, allowing readers to understand what the study set out to estimate.

The entry also highlights that outcomes may be available for different participants. Some completed the Month 6 questionnaire used for the primary outcome without attending secondary-outcome visits, and some attended visits without completing the questionnaire. This distinction matters statistically because the number of observations can differ by endpoint. It makes clear why a single enrollment count cannot substitute for outcome-specific denominators or a description of missing-data handling.

The record further illustrates the difference between a trial design and an analysis result. Randomization, a parallel-group structure, and a defined primary outcome describe the intended comparison, but do not reveal its estimate or precision. The absence of posted analyses means readers cannot assess the primary contrast from this record. That reporting limitation is especially important when the registry lists multiple outcomes and does not report how they were analyzed or prioritized.

Finally, the sample-size planning description distinguishes planning illustrations from the trial’s own design justification. Such illustrations depend on assumptions and should not be mistaken for observed power or for evidence about the result. Taken together, these features make the record useful for understanding the planned question while also showing why statistical interpretation requires outcome estimates, uncertainty, denominators, and analysis details.

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 registry record does not report the primary-outcome estimate or its 95% confidence interval. This is the central limitation for interpreting the study’s main question: the direction, magnitude, and precision of the between-group difference in mean PDQS change cannot be assessed. The record also does not report the underlying group-level baseline and six-month measurements or the number of participants contributing primary-outcome data.

Information about the statistical analysis is limited. The registry does not report the specific model or test, whether the analysis adjusted for baseline score or other factors, the analysis population, or the approach to missing data. It describes differing completion of primary questionnaires and secondary-outcome visits, but gives no counts or reasons. The extent to which missing primary data could affect interpretation is therefore not reported in the registry record.

The entry lists 12 outcome measures but does not report how they were prioritized, whether secondary analyses were prespecified, or whether multiplicity was addressed. It also does not report the sample-size justification used for the trial. The listed planning assumptions are described as illustrations based on the observed effect, rather than as the trial’s own design; they do not replace a reported design rationale or outcome analysis.

Other details relevant to judging the design are also not reported in the registry record, including the method of random sequence generation, allocation concealment, who was masked, and the criteria used to define high cardiovascular risk. The dietary intervention descriptions do not fully specify how personalized recommendations were delivered. These omissions limit assessment of implementation and generalizability, apart from the missing outcome results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Efficacy of Individualized Dietary Advice in Improving Diet Quality and Cardiovascular Health — NCT03854461.
• Registry record last updated 2025-08-17; status last verified 2025-08.
• Results first posted 2025-08-17.
• 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 a completed, randomized, single-masked, parallel-group dietary intervention with 162 enrolled participants at high risk of cardiovascular disease in Ireland, North and South. The study compared personalized dietary advice plus educational material with educational material over six months. Its primary endpoint was the between-group difference in mean change in PDQS from baseline to six months. The PDQS covers 21 food groups, ranges from 0 to 42, and assigns higher scores to better diet quality.

The record lists 12 outcome measures and describes differing completion of primary questionnaires and secondary-outcome visits at Month 6. It reports no analyses and does not report the primary-outcome estimate or confidence interval. Serious and other adverse events are listed as 0 in each group, with no deaths listed. The statistical result and several analysis details are not reported in the registry record.