Diet as a Potential Treatment for Autosomal Dominant Polycystic Kidney Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Diet as a Potential Treatment for Autosomal Dominant Polycystic Kidney Disease (NCT02225860), a randomized phase 2, phase 3 study. The primary outcome is Change in Mean Serum Copeptin From Baseline (a Reflection of Endogenous Vasopressin Production) at Week 2.

2. Clinical Question

The registry describes the study purpose as learning whether dietary habits can affect vasopressin secretion in people with ADPKD. Its stated rationale is that vasopressin is related to kidney cyst growth and disease progression. That rationale explains the choice of copeptin as a measure of interest, but it does not establish that a change in copeptin predicts a change in clinical disease outcomes. The posted primary result is an arm comparison of mean change in serum copeptin from baseline to week 2.

3. Trial Design

The registry record describes a completed, randomized, parallel-arm trial with no masking. It lists phase 2 and phase 3, a total enrollment of 34, and Tufts Medical Center as the sponsor. The record lists the start as 2014-05 and primary completion as 2016-02. Participants were allocated to diet and water adjustment or control, with 17 participants recorded in each arm. The trial summary describes a two-week study period and says blood and urine tests were performed 3 times during the study.

The intervention arm is described as reducing dietary salt and protein intake, alongside water adjustment. The control arm continued its usual diet. The registry summary describes random assignment as allocation by chance, but details of sequence generation, concealment, and the procedures used to implement assignment are not reported in the registry record. Masking is listed as none; further information about who knew the assigned intervention is not reported.

The primary endpoint was change in mean serum copeptin from baseline to week 2, measured in pmole/L. Two secondary outcomes are posted: change in total daily urinary solutes from baseline to week 2 and change in mean serum copeptin from baseline to week 1. The record lists 3 outcome measures overall, while results for two secondary outcomes are included in the posted results. The identity and results of any additional outcome measure are not reported in the registry record.

The registry describes the trial as completed. It does not report the trial’s original sample-size justification, the planned analysis population, the handling of missing observations, or detailed allocation procedures. The observed enrollment and arm sizes describe the participants represented in the posted results; they do not establish the original design assumptions.

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

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 Change in Mean Serum Copeptin From Baseline (a Reflection of Endogenous Vasopressin Production) at Week 2, measured over Baseline to week 2.

The primary endpoint is change in mean serum copeptin from baseline to week 2, expressed in pmole/L. Copeptin is described in the registry record as a reflection of endogenous vasopressin production. The endpoint therefore measures a laboratory marker chosen to assess whether the combined dietary and water intervention was associated with a difference in vasopressin-related activity over the study period.

Using change from baseline focuses the comparison on how the measured value shifted during the intervention period, rather than only comparing values at the endpoint. The posted results give the mean change within each arm and an estimated difference between those changes. A negative mean change indicates a decrease from baseline on the endpoint’s scale; the arm contrast indicates how the mean change in the intervention arm compares with the control arm. These are descriptions of the biomarker results, not direct measures of kidney cyst growth or disease progression.

Copeptin is used because of its stated relationship to endogenous vasopressin production and the trial’s biological rationale. That rationale does not by itself show that a measured change is a validated substitute for a patient-important outcome. The registry record does not report whether copeptin change was validated as a surrogate for clinical outcomes in this study. The endpoint addresses a short-term biological question; it cannot alone establish effects on longer-term health outcomes.

7. Results Posted in the Registry

• Diet and Water Adjustment: mean -0.86 versus 0.39 on control; difference -1.25 (95% CI -2.09 to -0.41), standardized effect d = -1.00; z-test p = 0.004.

8. Secondary Efficacy Endpoints

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

Change in Total Daily Urinary Solutes From Baseline to Week 2

• 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:
  • Diet and Water Adjustment: mean -120.00 versus 27.00 on control; difference -147.00 (95% CI -254.55 to -39.45), standardized effect d = -0.92; z-test p = 0.007.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Diet and Water Adjustment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change in Mean Serum Copeptin Level From Baseline to Week 1

• 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:
  • Diet and Water Adjustment: mean 0.90 versus 1.40 on control; difference -0.50 (95% CI -1.34 to 0.34), standardized effect d = -0.40; z-test p = 0.244.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Diet and Water Adjustment and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes provide context around the primary biomarker result, but they do not all show the same degree of separation between arms. The urinary-solute comparison has a negative estimated difference, while the week 1 copeptin comparison is less precise and its interval includes zero. Taken together, the secondary results do not establish a uniform pattern across measures and time points.

The urinary-solute measure concerns a different aspect of the intervention response, while week 1 copeptin concerns the same biomarker at an earlier time than the primary endpoint. These results can be considered alongside the week 2 primary comparison, but they do not independently validate it. A biomarker shift at one time point and an accompanying change in urinary solutes are not direct evidence of long-term clinical outcomes.

The registry posts two secondary outcome results, although it lists 3 outcome measures overall. The identity and result of any additional measure are not reported in the registry record. The record reports a sponsor t-test for the urinary-solute outcome, while no sponsor analysis is posted for week 1 copeptin. Recalculated comparisons should therefore be distinguished from the registry’s reported analyses.

Unadjusted secondary results carry less weight because evaluating multiple outcomes creates more opportunities for chance findings. Unless a multiplicity strategy is specified, nominal p-values do not account for that wider set of comparisons. The registry does not report a multiplicity adjustment or a detailed prespecified hierarchy for the secondary outcomes. Their results are best treated as exploratory context, not as a collection of independent confirmations or as a basis for claims beyond the primary endpoint.

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

• Change in Total Daily Urinary Solutes From Baseline to Week 2
• Change in Mean Serum Copeptin Level From Baseline to Week 1

9. Statistical Interpretation

10. Statistical Methods Explained

The primary comparison concerns a continuous outcome: change in serum copeptin. The registry reports the mean change and standard deviation for each arm, and the posted arm contrast is a mean difference. A mean summarizes the average observed change within an arm. The standard deviation describes how spread out individual changes are around that arm’s mean; it is not the uncertainty interval for the mean itself.

The recalculated contrast is obtained by comparing the intervention-arm mean change with the control-arm mean change, with the direction stated as intervention minus control. The reported estimate is -1.25 pmole/L. Its negative sign indicates a lower average change in the intervention arm on the copeptin scale. The same interpretation depends on keeping the stated arm order in mind; reversing the order would reverse the sign but not the underlying comparison.

A confidence interval gives a range of effect estimates compatible with the observed data and the model used to calculate it. The primary 95% interval extends from -2.091 to -0.409 pmole/L. Because the interval does not include zero, the posted estimate is distinguishable from a zero difference under the interval’s assumptions. The interval also communicates uncertainty about the magnitude: the data do not pin down a single exact difference.

The registry reports the sponsor’s primary analysis as a two-sided t-test. A t-test assesses evidence about a mean comparison while accounting for variability and sample size under its assumptions. “Two-sided” means the test considers differences in either direction rather than only a prespecified direction. The sponsor’s result is reported as p < 0.01. The recalculated unadjusted p-value is 0.004. The recalculation is based on posted summary statistics and is not a replacement for the sponsor’s analysis.

General statistical explanation: a p-value measures how unusual data at least as incompatible with the null comparison would be if that null and the test assumptions held. It is not an effect-size measure and does not measure clinical importance. A smaller p-value does not remove uncertainty about the estimated magnitude, which is why the effect estimate and confidence interval matter alongside it. The registry record does not report a detailed statistical analysis plan, and it does not report whether other adjustments or analyses were prespecified.

Standard deviations are relevant to the precision of a mean comparison because more variable observations generally make a group mean less precise when sample size is held fixed. General statistical explanation: confidence intervals for mean differences reflect both the variability of the outcome and the number of observations contributing to each arm. The posted primary result has 17 participants per arm. The standard deviations are 1.3 pmole/L in the intervention arm and 1.2 pmole/L in control.

The standardized effect-size estimate in the posted recalculation is -0.999. A standardized effect expresses a mean difference relative to a pooled measure of variation, making it unitless. It may help compare effect magnitudes across outcomes with different measurement units, but it does not replace the difference in the original unit or its confidence interval. The registry record does not report a sponsor-provided standardized effect estimate.

General statistical explanation: when outcome variability differs from a simple normal model or is especially uneven, conventional mean-based analyses may be less reliable, depending on the sample size and analysis assumptions. The posted results describe continuous outcomes using means and standard deviations, and the sponsor reports a t-test for the primary endpoint. The registry record does not report diagnostic checks, alternative models, or a detailed discussion of distributional assumptions, so those aspects cannot be assessed from the record.

The posted recalculations are unadjusted comparisons based on summary statistics. They are not adjusted for baseline covariates or for testing multiple outcomes. The record reports two-sided t-tests for the primary endpoint and urinary-solute secondary endpoint, while no sponsor analysis is posted for week 1 copeptin. Whether the sponsor used additional analyses not entered in the registry is not reported in the registry record.

Random allocation can help balance prognostic factors across arms on average, but a small study can still have imbalances by chance. The registry record does not provide enough participant-level characteristics to evaluate baseline balance. It also does not specify the analysis population, whether all randomized participants were included, or how missing outcome observations were handled. These omissions limit assessment of the assumptions behind the posted comparisons.

Finally, the analysis addresses a short-term mean difference for a biomarker. Statistical evidence about this endpoint should not be extended to outcomes that were not measured or reported. General statistical explanation: an estimate can be statistically distinguishable from zero and still leave important questions about generalizability, clinical relevance, and durability unresolved. Those questions depend on the outcome, study design, precision, and evidence beyond a single comparison.

11. Confidence Intervals and Precision

The primary mean difference is -1.25 pmole/L, with a 95% confidence interval from -2.091 to -0.409. The interval expresses uncertainty around the estimated difference: values throughout this range are compatible with the observed data and the calculation’s assumptions. Its position below zero indicates that the posted interval supports a negative intervention-minus-control contrast, while its width shows that the exact magnitude remains uncertain.

The interval is based on 17 participants in each arm. The arm-specific standard deviations are 1.3 pmole/L and 1.2 pmole/L. These summaries describe variation among participants, while the confidence interval describes uncertainty in the estimated contrast. The two should not be treated as interchangeable. A small sample can yield an imprecise estimate even when the observed arm means differ, and the confidence interval is a more direct guide to precision than the p-value alone.

The interval does not capture every source of uncertainty. It relies on the statistical model and the available observations. The registry record does not report how missing outcome data were handled, the analysis population, or diagnostic checks for the model assumptions. It is therefore not possible to judge those sources of uncertainty from the posted registry information.

The confidence interval also applies to the specific endpoint and timeframe: change in serum copeptin from baseline to week 2. It does not describe the precision of an effect on kidney function, cyst growth, or long-term clinical outcomes. Statistical precision for this biomarker comparison should not be mistaken for precision about outcomes the trial did not report.

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 80% power and participants per arm for 90% power. They are not total events; the event-count convention applies to time-to-event outcomes, whereas these continuous outcomes use participants per arm. The planning assumptions listed in the registry record are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each row considers an effect equal to a stated fraction of the observed effect.

The 80% power column gives the estimated participants per arm needed for an 80% chance of detecting the specified effect under those planning assumptions, if that effect and the assumptions hold. The 90% column gives the corresponding planning figure for a 90% chance. These are design illustrations, not guarantees about the results of a future study. The trial’s original sample-size justification and original design assumptions are not reported in the registry record.

The figures vary with the effect being targeted. Planning for 75% of the observed effect or 50% of the observed effect requires more participants than planning for 100% of the observed effect. This illustrates a general principle: smaller effects are harder to distinguish from random variation, so more participants are typically needed to achieve the same planned power. The observed enrollment was 34, with 17 participants per arm; the planning figures do not change that observed sample size.

This is not observed power. It is a planning illustration calculated from the observed effect, not a retrospective measure of how likely the completed trial was to find a result. The observed estimate is itself uncertain, so a planning calculation based on it should not be read as proof that the effect will recur at the same magnitude.

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 = -1.250; pooled standard deviation σ = 1.251.
2. n = 2 × (1.96 + 0.842)² × 1.251² / -1.250² = 15.7, rounded up to 16 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 <- -1.25                      # observed difference in means
sigma <- 1.25099960031968                     # 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(2225860)
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 = 16 (80% power), 22 (90% power)
 75% of observed effect: n per arm = 28 (80% power), 38 (90% power)
 50% of observed effect: n per arm = 63 (80% power), 85 (90% power)
power.t.test: 16.7 
Simulated power at n = 16 per arm: 0.778 (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. Analyses Reported by the Sponsor

The registry’s own primary analysis is a two-sided t-test and reports p < 0.01. The posted analysis does not include the sponsor’s numerical estimate of the mean difference or its confidence interval. The recalculated unadjusted comparison from the posted arm summaries gives a mean difference of -1.25 pmole/L, a 95% confidence interval from -2.091 to -0.409, and p = 0.004.

The registry does not flag a discrepancy between the posted results and the recalculation. The sponsor’s analysis remains the trial’s reported analysis; the recalculation is a transparent, unadjusted check based on the arm-level means, standard deviations, and sample sizes. Its p-value is consistent in broad terms with the sponsor’s reported p-value category, but the registry does not provide enough detail to determine whether the calculations use exactly the same procedures or analysis population.

The sponsor’s analysis takes precedence if a discrepancy is identified. No discrepancy is flagged in the record. The recalculated estimate and interval are useful for understanding the direction and precision of the contrast, but they should not be represented as additional sponsor-reported results or as a substitute for an analysis based on participant-level data.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures and posts results for a primary endpoint and two secondary outcomes. It reports analyses for the primary endpoint and urinary-solute outcome, but no sponsor analysis is posted for week 1 copeptin. A detailed statistical analysis plan, including any prespecified hierarchy among outcomes, is not reported in the registry record.

Multiplicity arises when several outcomes, time points, or comparisons are examined. General statistical explanation: without an adjustment or a prespecified strategy, the chance of observing at least one apparently unusual result can increase as more comparisons are made. The registry record does not report a correction for multiple testing. The secondary results should therefore be interpreted with caution and should not be treated as independent confirmatory tests.

Information on missing data is not reported in the registry record. The record does not state whether outcome measurements were missing, how any missing values were handled, or whether sensitivity analyses were performed. The analysis population is also not reported. Although the posted arm counts are 17 in each group, the record does not say whether the primary analysis included every randomized participant or how exclusions, if any, were handled.

Other aspects of the analysis plan are also not reported in the registry record, including baseline adjustment, covariate adjustment, diagnostic checks, and procedures for handling protocol deviations. These omissions do not establish that such procedures were absent; they mean the registry entry does not allow them to be assessed. The randomized parallel design supports an arm comparison, but interpretation still depends on how participants and outcome observations entered the analysis.

For these reasons, the posted primary result can be described as an unadjusted comparison of mean changes, while the details needed to evaluate multiplicity and missing-data assumptions remain unavailable in the registry record. That distinction matters when interpreting the nominal p-values and the apparent consistency of the secondary findings.

16. Safety Results

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

Other (non-serious) adverse events

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

The registry reports 0 serious adverse events among 17 participants at risk in the diet-and-water-adjustment arm and 0 among 17 participants at risk in control. These figures describe serious adverse events recorded in the posted safety results during the trial. They do not demonstrate that the risk of serious events is absent; a study of this size and duration may provide limited information about uncommon events.

The registry also records 0 other adverse events among 17 participants at risk in each arm. Death counts are not reported in the registry record. No serious adverse event terms are listed. The record does not provide event-level descriptions, timing, severity beyond the serious/non-serious classification, or a detailed account of how adverse events were collected.

These safety counts should be read as the observations recorded in this trial, not as a broad estimate of safety in other populations or over longer periods. Zero reported events in an arm is not equivalent to proof that no risk exists. The short study timeframe and small enrolled sample limit what these figures can establish.

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

The central statistical finding is a negative difference in mean change in serum copeptin between the diet-and-water-adjustment and control arms from baseline to week 2. The recalculated mean difference is -1.25 pmole/L, and the 95% confidence interval ranges from -2.091 to -0.409. The sponsor reports a two-sided p-value below 0.01. These figures describe the observed short-term biomarker comparison and its statistical uncertainty.

The endpoint is a reflection of endogenous vasopressin production, according to the registry description. That makes it relevant to the biological question motivating the study, but the result does not show that kidney cyst growth changed or that disease progression slowed. The record does not report those outcomes as results. It also does not establish that a change in copeptin predicts a change in clinical outcomes.

The intervention combined diet and water adjustment. The registry does not separate the effects of salt reduction, protein reduction, and water intake. The result therefore cannot identify which component, if any, accounts for the observed arm difference. It also cannot determine whether the same difference would be seen with different instructions, adherence, or participant characteristics.

With 34 participants and a short study period, the findings are limited in scale and duration. The confidence interval gives a range of values compatible with the primary data and analysis assumptions, but it cannot resolve limitations related to missing-data handling or analysis populations, which are not reported. The secondary results offer context but are unadjusted for multiplicity and do not turn the primary biomarker result into evidence about long-term outcomes.

The appropriate interpretation is therefore specific: the posted results show a difference in mean copeptin change between these randomized arms over the stated timeframe. They do not by themselves establish clinical benefit, lack of benefit, safety beyond the recorded observations, or effects on outcomes that were not reported. Broader conclusions require evidence addressing those outcomes and the limitations of this small, short-term trial.

18. Why This Trial Matters Statistically

This trial is statistically informative because it links a randomized comparison to a clearly defined biological measure and reports both arm-level changes and an arm contrast. The primary endpoint is continuous, so the mean difference retains the original measurement unit and can be read alongside its confidence interval. The registry also reports the sponsor’s two-sided t-test, allowing the reported inferential result to be compared with an unadjusted recalculation from the posted summaries.

The example illustrates why effect estimates and uncertainty intervals matter in addition to p-values. The p-value indicates evidence against a zero-difference null under the test assumptions, while the interval shows a range of plausible effect magnitudes. Neither alone answers whether the difference matters clinically. The endpoint is a short-term biomarker, and the record does not establish its connection to later clinical outcomes in this trial.

The study also shows the limits of small trial results. With 17 participants per arm, estimates can be sensitive to sampling variation, and the registry does not report participant-level information needed to assess baseline balance or missing-data handling. The planning illustrations show how required sample sizes depend on the effect targeted, but they are not a substitute for the original design justification, which is not reported.

Finally, the secondary outcomes and incomplete reporting of analysis details demonstrate why the number of outcomes and the prespecified analysis strategy matter. Unadjusted secondary findings may be useful for generating questions, but they carry less confirmatory weight when a multiplicity approach is not reported. The trial is a useful case for separating a statistical signal in a biomarker from the broader claims that the data cannot establish.

19. 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 enrollment was 34, with 17 participants in each arm, and the study period is described as two weeks. These features restrict the amount of information available about the size and durability of the primary contrast. The registry does not report the original sample-size justification, so it is not possible to determine what effect the trial was designed to detect or which assumptions informed that design.

The intervention combined dietary salt and protein reduction with water adjustment. The record does not report the exact dietary or water targets, adherence, or the extent to which participants followed the instructions. Because the intervention is combined, the posted comparison cannot distinguish the contribution of its separate elements.

The registry record does not report participant characteristics in sufficient detail to assess how representative the enrolled group was, nor does it provide information needed to evaluate baseline balance. It does not report the analysis population, missing outcome data, handling of missingness, or sensitivity analyses. These gaps limit assessment of how robust the results are to analytic choices.

Masking is listed as none. The record does not describe whether outcome assessment or laboratory analysis was conducted without knowledge of assignment. The registry also does not report a detailed statistical analysis plan or a multiplicity adjustment. There are 3 listed outcome measures, with results posted for two secondary outcomes, and the status of the remaining measure is not reported.

Finally, the primary endpoint is a short-term biomarker rather than a reported clinical outcome. The record does not establish that the observed copeptin difference corresponds to changes in kidney function, cyst growth, symptoms, or long-term disease course. The trial’s safety observations are also limited by the small sample and short timeframe; death counts are not reported in the registry record.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Diet as a Potential Treatment for Autosomal Dominant Polycystic Kidney Disease — NCT02225860.
• Registry record last updated 2017-03-30; status last verified 2017-02.
• Results first posted 2017-03-30.
• 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.

23. Record Summary

NCT02225860 is a completed randomized, unmasked, parallel-arm study sponsored by Tufts Medical Center. It enrolled 34 participants with autosomal dominant polycystic kidney disease, with 17 participants in each arm. The intervention combined diet and water adjustment; control participants continued their usual diet. The primary endpoint was change in mean serum copeptin from baseline to week 2.

The sponsor reported a two-sided t-test with p < 0.01 for the primary analysis. The recalculated unadjusted mean difference was -1.25 pmole/L, with a 95% confidence interval from -2.091 to -0.409. These results concern a short-term biomarker comparison. The record does not report the original sample-size justification, analysis population, missing-data handling, or multiplicity strategy, and it does not establish effects on long-term clinical outcomes.