Kidney Transplant Low-AGE Diet Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Kidney Transplant Low-AGE Diet Study (NCT05104242), a randomized na study. The primary outcome is Skin Autofluorescence (SAF) Levels at 6 Months.

2. Clinical Question

3. Trial Design

The registry describes a completed, randomized, parallel-group study with no masking. Its title identifies it as a feasibility study of a low AGE diet in kidney transplant recipients. The stated purpose was to test the feasibility of a larger randomized controlled trial investigating the diet, SAF levels, and cardiovascular health. The record lists enrollment as 38. It gives a start date of 2022-02-04 and a primary completion date of 2022-12-08.

The two groups were a standard-diet control group and a low AGE diet intervention group. Both diets were described as having the same calorie and protein targets; the intervention was intended to reduce dietary AGE content by changing cooking methods. The description of the intervention ends after mentioning avoidance of dry heat methods, so further dietary instructions are not reported in the registry record. Randomization methods, allocation concealment, and the process used to deliver or monitor the diets are not reported in the registry record. The record specifies no masking.

The primary outcome was mean SAF at 6 months, measured in arbitrary units. The posted primary results include 17 participants in the control group and 13 in the intervention group. These outcome counts do not account for the registry enrollment figure; the reason for the difference is not reported in the registry record. The record does not explain whether the outcome groups reflect follow-up completion, exclusions, or a particular analysis population.

Secondary outcomes listed in the record were diet adherence, SAF trend over 0, 3 and 6 months, and dietary AGE intake at 6 months. No detailed comparative result for dietary AGE intake is reported in the registry record. The analysis plan, sample-size justification for this feasibility study, and any prespecified rules for handling missing observations 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.

Before assignment: Of the 48 kidney transplant recipients assessed for eligibility, 10 did not meet the inclusion criteria: 9 had skin autofluorescence levels below the general population mean value for age and 1 was classified as being malnourished according to the Subjective Global Assessment).

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Skin Autofluorescence (SAF) Levels at 6 Months, measured over 6 months.

The primary endpoint was mean skin autofluorescence (SAF) at 6 months, expressed in arbitrary units. The registry describes SAF as a measure of tissue accumulation of advanced glycation end-products. It was assessed with a validated Autofluorescence Reader. The instrument calculates SAF as a ratio between emission and excitation; three measurements were conducted and their average was used for statistical analysis.

SAF was selected because the study concerned dietary AGE exposure and its possible relationship to tissue AGE accumulation. It is therefore a measure relevant to the biological question being explored, rather than a direct measure of cardiovascular health. The registry’s broader purpose mentions cardiovascular health, but the primary endpoint reported for this comparison is SAF. Cardiovascular outcomes are not identified as the primary endpoint in the registry record.

The record gives a reference value of 2.1±0.4 AU for the age group of 50-60 years. That reference is not a comparison group in this trial. Participant ages and the applicability of the reference value to the study groups are not reported in the registry record. SAF is expressed in arbitrary units, so interpretation depends on the measurement approach and the context of the recorded values. The endpoint definition does not establish a threshold for a meaningful change, and such a threshold is not reported in the registry record.

7. Results Posted in the Registry

• Low AGE Diet - Intervention Group: mean 2.80 versus 2.80 on control; difference 0.00 (95% CI -0.39 to 0.39), standardized effect d = 0.00; z-test p = 1.000.

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.

Participant Adherence to Diets

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Low AGE Diet - Intervention Group: 69.2% (9/13) versus 100.0% (17/17) on control; risk difference -30.8 percentage points (95% CI -55.9 to -5.7), risk ratio 0.69 (0.48–0.99); unadjusted two-proportion z-test p = 0.014.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Low AGE Diet - Intervention Group than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Skin Autofluorescence (SAF) Trend.

• 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:
  • Low AGE Diet - Intervention Group: mean -0.45 versus -0.22 on control; difference -0.23 (95% CI -0.97 to 0.51), standardized effect d = -0.24; z-test p = 0.542.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Low AGE Diet - Intervention Group and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes provide complementary information, but they address different aspects of the study. Adherence describes participation in the assigned dietary approach; SAF trend concerns change over repeated measurement times; dietary AGE intake concerns exposure rather than the primary tissue measurement. These outcomes can help characterize feasibility and the relationship between the intervention and the proposed biological measure, but they are not interchangeable with the primary 6-month SAF comparison.

Across the posted secondary results, the adherence comparison is the one with an unadjusted result indicating a between-group difference. The SAF trend estimate, in contrast, has uncertainty that includes no difference. The record lists dietary AGE intake at 6 months as a secondary outcome, but numerical comparative results for it are not reported in the registry record. This pattern does not establish a consistent chain from dietary assignment through measured intake to SAF. The available information is not sufficient to determine why the secondary outcomes differ in their apparent signals.

Unadjusted secondary findings carry less weight than a prespecified primary comparison when several outcomes are examined. General statistical interpretation: testing multiple outcomes can increase the chance that at least one result appears noteworthy by chance, particularly if the outcomes are interpreted without a correction or a predeclared hierarchy. The registry record does not report an adjustment for multiplicity, a hierarchy for secondary outcomes, or a confirmatory analysis plan. The secondary findings are therefore best treated as exploratory context rather than as independent proof of an effect.

The secondary results may be useful in planning or refining a larger study, especially because feasibility and adherence are part of the stated purpose. However, the record does not provide enough detail about how adherence was defined, how dietary intake was measured, or how missing secondary observations were handled. Those details would be important for judging whether the observed pattern reflects the intervention, measurement choices, or incomplete follow-up. The secondary outcomes should be interpreted alongside, not substituted for, the primary SAF result.

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

• Participant Adherence to Diets
• Skin Autofluorescence (SAF) Trend.
• Dietary AGE Intake at 6 Months

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: each participant has a SAF measurement expressed in arbitrary units, and the registry reports the mean and standard deviation for each group. A mean describes the center of a set of measurements. A standard deviation describes how spread out individual measurements are around that mean. General statistical interpretation: the standard deviation is not the uncertainty of the group mean; the uncertainty in a mean also depends on the number of observations and the analysis assumptions.

What does the mean difference represent?

The posted comparison is a mean difference, with the low AGE diet group compared against the standard-diet control group. The estimated difference is 0.0, while the group means are both 2.8. Because the estimate is expressed on the original SAF scale, it retains the endpoint’s units and can be read as a difference in arbitrary units. A mean difference is not a statement about every participant: individual measurements can vary even when the group means are equal.

The comparison also reports a pooled standard deviation of 0.559 and a standardized effect, d, of 0.0. General statistical interpretation: a standardized effect expresses a difference relative to variability, which can help describe the size of a contrast on a scale that is less tied to the endpoint’s original units. It does not create a clinical interpretation by itself. The registry record does not report a threshold that would identify a meaningful SAF difference.

How should the confidence interval and p-value be read?

The 95% confidence interval for the primary mean difference runs from -0.394 to 0.394. General statistical interpretation: a confidence interval gives a range of estimates compatible with the data and the procedure used, and reflects uncertainty in the estimated contrast. It does not mean that 95% of individual participant measurements fall inside that range. The interval includes zero, which corresponds to no difference in means, and values on both sides of zero. The unadjusted p-value is 1.0. A p-value measures how unusual the data would be under a specified null model and test; it is not the probability that the null model is true. The exact test and model are not reported in the registry record.

The record labels the comparison p-value unadjusted. That matters because multiple outcomes can create several opportunities for apparently noteworthy results. An unadjusted p-value does not account for a family of tests unless an adjustment has been applied. The registry record does not report a multiplicity adjustment or a prespecified hierarchy for interpreting the outcomes.

Why do uncertainty and study size matter?

Smaller outcome groups generally leave less information for estimating group means and differences than larger groups, all else being equal. General statistical interpretation: a wider interval indicates less precision, while a narrower interval indicates greater precision under the chosen model. The primary interval allows for differences in either direction, so the point estimate alone should not be used to claim that no difference is possible. The outcome counts are 17 for control and 13 for intervention, while registry enrollment is 38. The record does not explain the difference or report how missing data or exclusions were handled.

For the secondary SAF trend outcome, the observed mean difference was -0.23 arbitrary units per year, with a 95% confidence interval from -0.969 to 0.509 and an unadjusted p-value of 0.542. The record also gives planning illustrations based on that observed effect: for planning for 100% of the observed effect, it lists 276 participants per arm for 80% power and 369 participants per arm for 90% power; for planning for 75% of the observed effect, 490 participants per arm for 80% power and 656 participants per arm for 90% power; and for planning for 50% of the observed effect, 1,102 participants per arm for 80% power and 1,476 participants per arm for 90% power. These are illustrative future-study calculations, not observed power for this trial.

The planning assumptions stated in the record are a two-sided significance level of 0.05, equal allocation between arms, a normal approximation, and an effect to detect equal to the stated fraction of the observed effect. The record says these calculations are based on the observed effect, not the trial’s own design. Such projections depend on the estimated effect and the assumptions used; they should not be treated as a sample-size justification for the present study. The record does not report the trial’s own sample-size rationale.

What is not specified about the analysis?

The registry record does not report whether the primary comparison used a particular parametric test, whether covariates were included, or whether an intention-to-treat or per-protocol population was used. It also does not report imputation, sensitivity analyses, or methods for accounting for repeated measurements. The SAF trend outcome covers measurements at 0, 3 and 6 months, but the statistical model used to derive the annual trend is not reported. These omissions limit how far the posted summary statistics can be used to reconstruct the analysis.

11. Confidence Intervals and Precision

The primary mean difference is 0.0 arbitrary units, with a 95% confidence interval from -0.394 to 0.394. This interval gives a more complete account of the result than the point estimate alone. It includes the no-difference value and a range of possible differences in both directions. Accordingly, the observed equality of group means should not be read as proof that the underlying group means are identical.

General statistical interpretation: a confidence interval reflects the uncertainty of an estimate under the method and assumptions used. It is not a range containing 95% of participant values, nor is it a probability statement about the fixed true effect. The interval’s width indicates that the data do not pinpoint a single precise difference. The registry record does not state what SAF difference would be important to patients or clinicians, so the interval cannot be classified against a reported importance threshold.

The unadjusted p-value of 1.0 is consistent with the reported estimate at zero, but it does not remove uncertainty. A p-value is not a measure of precision or effect size. The estimate, interval, and study context should be considered together, particularly because the reported outcome groups are limited in size and the record does not explain the difference between enrollment and the outcome counts.

The secondary SAF trend estimate has a wider interval, from -0.969 to 0.509 arbitrary units per year. It also includes zero. The planning illustrations based on that observed trend effect show how the required number of participants per arm changes when planning for different fractions of the observed effect. They are not observed power calculations and do not make the present estimate more precise. Since the record does not report a sample-size justification for this feasibility study, those illustrations should be viewed only as conditional planning scenarios.

12. Multiplicity, Missing Data and Analysis Populations

Several outcomes are listed: the primary SAF measurement at 6 months and secondary measures of adherence, SAF trend, and dietary AGE intake. When multiple outcomes are assessed, the chance of observing at least one apparently unusual result can rise if each is tested separately. General statistical interpretation: multiplicity methods, such as adjusting significance thresholds or defining a hierarchy of outcomes, can help control how strongly a set of results is interpreted. The registry record does not report a multiplicity adjustment or a prespecified hierarchy.

The secondary adherence result has an unadjusted p-value of 0.014. Since the record does not describe how the family of outcomes was handled, that value should be read as unadjusted rather than as a multiplicity-controlled confirmatory result. This does not invalidate the observation; it places limits on how strongly it can support a broader claim. The primary comparison is also reported with an unadjusted p-value, and no adjustment method is described.

The record lists registry enrollment as 38, while primary outcome results are reported for 17 control participants and 13 intervention participants. It does not explain this difference, state whether all enrolled participants were analyzed, or identify the analysis population. It is therefore not possible from the registry record to determine whether the analysis followed an intention-to-treat principle, a per-protocol principle, or another rule.

Missing-data handling is also not reported. The registry record does not describe the number or reasons for missing measurements, imputation, sensitivity analyses, or whether participants with incomplete follow-up contributed to any analyses. For the repeated SAF trend, it does not state how measurements at 0, 3 and 6 months were handled when any time point was unavailable.

The record does not report an interim-analysis plan, stopping rules, or a statistical analysis plan. These omissions do not show that such procedures were absent; they mean that they are not documented in the registry record. Without these details, the results are most appropriately interpreted as posted outcome summaries with unadjusted comparisons and unresolved questions about analysis populations, missingness, and multiplicity.

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 serious adverse event figures list 19 participants at risk in each group, with 0 serious adverse events and 0 deaths in each group. The record does not list any serious event terms. These figures describe the safety counts recorded for the listed at-risk groups during the reporting period; they do not show that the groups had identical overall safety experience or that an event could not occur.

For other adverse events, the record lists 0 participants at risk and 0 affected in both groups. Because the record does not specify further details about non-serious event collection or reporting, those entries should not be interpreted as evidence that no non-serious events occurred. The period covered, surveillance procedures, and criteria for classifying events are not reported in the registry record.

Zero recorded serious events in a feasibility study is reassuring only in the narrow descriptive sense that none are listed in these results. It does not establish safety, particularly when the record provides limited detail about event monitoring and the study’s size and duration. The figures are not a basis for medical advice or for conclusions about risks beyond the participants and reporting reflected in the registry record.

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

The posted primary results show identical mean SAF values at 6 months in the two diet groups, with an estimated mean difference of 0.0 arbitrary units. The confidence interval includes zero and also allows for differences in either direction. The result therefore describes what was observed in the reported outcome groups; it does not prove that the diets have the same effect or rule out a potentially meaningful difference.

The primary endpoint is SAF, a measure of tissue AGE accumulation. It is not a direct measure of cardiovascular health. Although the study’s stated purpose includes exploring a larger trial concerned with cardiovascular health, the posted primary comparison does not answer whether cardiovascular outcomes differ. Nor does this result establish whether dietary AGE exposure changed, because numerical comparative results for dietary AGE intake at 6 months are not reported in the registry record.

The study is described as a feasibility study, which places the findings in a context of assessing whether a larger trial could be conducted. The registry record lists a difference between enrollment and the numbers in the primary outcome groups, but does not explain it. Details on eligibility, missing follow-up, and analysis populations are also not reported. These gaps make it difficult to judge how representative the posted outcome groups are of all enrolled participants.

The secondary adherence result and the SAF trend result should be regarded as exploratory in the absence of a reported multiplicity plan. They may inform questions for future research, but they do not replace the primary comparison or establish a consistent effect across all stages of the proposed pathway. The sample-size calculations based on the observed SAF trend are planning illustrations under stated assumptions, not observed power and not a guarantee that a future study will produce a particular result.

Finally, the absence of listed serious adverse events and deaths is a descriptive safety finding, not proof that the diet is risk-free. Taken together, the registry results are best understood as limited estimates from a feasibility study, with important uncertainty and incomplete reporting about analysis details. No treatment recommendation follows from these statistics.

15. Why This Trial Matters Statistically

This trial matters statistically because feasibility studies can expose practical and analytical questions that need to be resolved before a larger randomized study. The registry describes an intervention that changes food preparation while seeking to hold calories and protein targets similar between groups. The presence of an adherence outcome reflects one important aspect of evaluating whether participants follow the intended dietary approach. The study also reports SAF, the measure proposed as the main biological endpoint.

The primary estimate is centered at no observed difference, but its confidence interval spans differences in either direction. That combination illustrates why an estimate should not be reduced to a p-value or interpreted as proof of no effect. A small feasibility study can produce a useful preliminary estimate while still leaving substantial uncertainty. The registry record does not report a threshold for a meaningful difference, so the statistical interval cannot be translated into a judgment about clinical importance.

The posted secondary results raise a further planning issue: adherence and SAF trend do not show the same statistical pattern. A larger study would need clear outcome definitions, a prespecified analysis plan, and an approach to interpreting multiple outcomes. It would also need transparent reporting of the analysis population and missing-data handling. Those elements help readers distinguish a primary confirmatory question from exploratory signals.

The planning illustrations based on the observed trend emphasize that sample-size requirements depend on the effect a study aims to detect and the assumptions used. They are scenarios rather than observed power, and the registry record says they are not the design basis for this feasibility study. The record does not report its own sample-size justification. This distinction is important when preliminary estimates are used to inform future research: uncertainty in an observed effect should be considered rather than treating it as a known target.

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 are specific to the information recorded for this study. The registry lists enrollment as 38, whereas the primary results report outcome groups of 17 and 13. The reason for this difference, participant flow, and the number or reasons for missing measurements are not reported in the registry record. Without that information, readers cannot assess how the outcome groups relate to all enrolled participants.

The record describes the study as randomized and unmasked, but does not report the randomization sequence method, allocation concealment, or details of how the dietary approaches were implemented. The intervention description is incomplete after the listed dry-heat cooking methods. The record also does not describe how adherence was defined or assessed, or how dietary AGE intake was measured. These details would help in judging the fidelity and comparability of the dietary conditions.

Statistical reporting is limited. The exact methods used for the primary comparison and repeated SAF trend are not reported, nor are covariate adjustment, missing-data methods, the analysis population, or sensitivity analyses. A multiplicity plan is not reported despite several outcomes. The registry record also does not report a clinically meaningful SAF difference, an equivalence margin, or the sample-size justification for the feasibility study.

The sample-size illustrations use an observed secondary trend effect and stated planning assumptions. They may be sensitive to the preliminary estimate and should not be treated as observed power or as a confirmed design requirement. The record’s safety entries provide little detail about event collection and do not support conclusions about non-serious events. These reporting gaps limit the precision and scope of interpretation; they do not by themselves establish that procedures were not conducted.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Kidney Transplant Low-AGE Diet Study — NCT05104242.
• Registry record last updated 2024-12-06; status last verified 2024-12.
• Results first posted 2024-12-06.
• 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

The registry record describes NCT05104242, the Kidney Transplant Low-AGE Diet Study, as a completed randomized parallel-group feasibility study with no masking. It lists enrollment of 38 and evaluates a low AGE diet against a standard diet in kidney transplant recipients. The primary outcome is mean SAF at 6 months, measured in arbitrary units.

The reported primary means are 2.8 in both groups. The estimated mean difference is 0.0, with a 95% confidence interval from -0.394 to 0.394 and an unadjusted p-value of 1.0. Secondary outcomes include diet adherence, SAF trend, and dietary AGE intake. The record also lists no serious adverse events or deaths in either group.

The registry record does not explain the difference between enrollment and the primary outcome group counts, or report the statistical analysis plan, missing-data handling, multiplicity approach, or the feasibility study’s own sample-size justification. Its results are preliminary registry summaries and should be interpreted with the uncertainty and reporting limits described.