Effects of Kuvan on Melatonin Secretion: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Kuvan on Melatonin Secretion (NCT01617070), a na phase 4 study. The primary outcome is Serum Melatonin at the End of 4 Weeks.

2. Clinical Question

The study concerns melatonin as a possible marker related to serotonin in individuals with PKU. Its brief summary also states that the investigators considered urine dopamine levels and hypothesized that Kuvan might improve melatonin secretion and urine dopamine levels to some extent, with potentially greater responses during combined treatment. These statements describe the investigators’ hypotheses, not findings.

The clinical question is therefore framed around measurements under several conditions in one group, rather than a treatment-versus-control question between separate groups. The registry record does not report a numerical estimate of the melatonin change under any condition, the uncertainty around such an estimate, or a statistical comparison among conditions. It also does not report numerical urine dopamine results. Without those outcome results, the stated hypotheses cannot be evaluated from the registry record.

3. Trial Design

The registry identifies this as a Phase 4 study with a single-group model. Allocation is recorded as not applicable, and masking is recorded as none. The record describes one group undergoing four conditions: washout, LNAA only, Kuvan only, and LNAA plus Kuvan. Each phase is described as lasting 4 weeks. No separate control group or randomized allocation between groups is described.

The enrollment field lists 10, while the arm description says one group of 12 subjects. Those entries do not agree, and the reason for the difference is not reported in the registry record. The primary outcome description says participants who completed all phases were measured; the number who completed all phases is not reported in the registry record. These entries should not be treated as interchangeable counts.

The study dates in the record are a start in 2012-05 and primary completion in 2014-12. Its status is completed. These registry entries describe the study’s recorded administrative status and design, not the outcome of the interventions.

Although measurements under several conditions in the same group may allow within-person comparisons in principle, the registry record does not report the condition order, whether order was assigned, or how periods were handled in the analysis. It also does not report any statistical analysis for the primary outcome: the number of analyses is recorded as 0. A protocol for statistical comparisons, treatment of repeated measurements, or adjustment for period effects is not reported in the registry record.

The record names the University of Southern California as sponsor. It identifies the interventions as a drug, Kuvan, and a dietary supplement, Large Neutral Amino Acid Therapy. These classifications and the listed conditions do not establish how participants used the interventions beyond the brief condition descriptions in the registry.

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.

LNAA (4 Weeks)

Washout (4 Weeks)

BH4 Therapy (4 Weeks)

BH4 and LNAA (4 Weeks)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Participates who completed all phases were measured.

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 Serum Melatonin at the End of 4 Weeks, measured over measured every 4 weeks up to 16 weeks.

The primary endpoint is serum melatonin at the end of 4 weeks, reported in pg/ml as a mean with standard deviation. The record says it was measured every 4 weeks up to 16 weeks and evaluated for each subject under four conditions: washout, LNAA only, Kuvan only, and LNAA plus Kuvan. The stated population for this measure is participants who completed all phases.

Melatonin is the outcome selected for the trial’s main question because the study is described as evaluating melatonin secretion as a marker of decreased serotonin in individuals with PKU. The brief summary says the investigators hypothesized that Kuvan, alone or combined with LNAA, might affect melatonin secretion. That rationale explains the endpoint’s role in the study; it does not demonstrate that melatonin is a validated marker or that a change in it corresponds to a clinical benefit. Such validation or clinical interpretation is not reported in the registry record.

A mean describes the average measured level in the analyzed group, while a standard deviation describes variation among the measurements. These are descriptive summaries, not by themselves evidence of a difference between conditions. To interpret a comparison, readers would also need the numerical summaries, the analysis method, and an estimate of uncertainty for the contrast of interest. Those numerical endpoint results and comparison estimates are not reported in the registry record.

The measurement schedule and completion-based population also matter for interpretation. The record does not state how incomplete measurements were handled, how many participants contributed to each condition, or whether all scheduled measurements were available. Those details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods for the primary endpoint are not reported in the registry record. The record identifies serum melatonin as a continuous measure summarized by a mean and standard deviation, but it does not identify a statistical test, model, contrast, confidence interval method, or approach to repeated measurements. The following explanations are general and clarify what those methods would mean; they do not describe analyses confirmed in this study.

What does a mean describe?

For a continuous outcome, the mean is the arithmetic average of the measurements included in an analysis. It gives a summary of the measured level in that analyzed set, but it does not show whether every participant had a similar value. The standard deviation describes how spread out measurements are around the mean. A larger spread indicates more variability among the observed values; it is not the same as uncertainty in the estimated mean.

Condition-specific means can describe the data, but comparing means requires clarity about which participants and observations were included. In a repeated-condition study, one possible target is the average difference within participants between two conditions. A comparison of group means that ignores the pairing can answer a different question and may fail to use the structure of the data. The registry record does not say whether the primary comparison was based on within-person differences or another approach.

Why does a confidence interval matter?

In general, a confidence interval expresses the statistical uncertainty around an estimated quantity, such as a mean difference. It is interpreted in relation to the data and the method used to construct it. A narrow interval indicates greater precision under that method, while a wide interval indicates less precision. An interval is not a guarantee that the true value lies within its particular limits, and it does not resolve possible bias in how the study was conducted or analyzed.

No confidence interval for serum melatonin or a condition contrast is reported in the registry record. Without an estimate and its uncertainty, it is not possible to assess how precisely the study distinguishes among conditions. A p-value alone, if one were available, would not give the magnitude or precision of a difference; the record does not report a p-value for this endpoint either.

Why is the study structure relevant to analysis?

General statistical principle: measurements from the same person are often correlated. A model or test that accounts for within-person dependence can reflect that pairing, whereas treating the observations as independent may misrepresent uncertainty. Repeated-measures methods can also account for condition and time, depending on the design and data. The choice should follow the actual allocation, measurement schedule, and estimand. The registry record does not report a repeated-measures model or any other analysis plan.

Condition sequence can matter when observations are collected over time. In general, a later measurement can differ from an earlier one because of time trends or the conditions that preceded it. Whether these effects are relevant depends on the protocol and actual sequence. Here, the registry describes four 4-week conditions but does not report their order or a method for handling order or period effects. It also does not report whether any carryover assessment was planned or performed. These omissions prevent a reader from determining how those concerns were addressed.

What do the sample-size assumptions describe?

The registry includes planning assumptions for an illustration based on an observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. For continuous-outcome illustrations, the stated convention is participants per arm for the listed power level; time-to-event illustrations use total events. These are planning assumptions, not a description of this study’s allocation, which is recorded as a single group with allocation not applicable.

The record does not report the trial’s own sample-size justification. The numerical observed effect used for the planning illustration and the resulting planning sample sizes are not reported in the registry record. Any such illustration is a planning exercise, not observed power and not evidence that the trial was adequately or inadequately sized. No claim about the trial’s power can be made from the information recorded.

Why does variation affect precision?

General statistical principle: greater variability in an outcome can make an estimated contrast less precise when other aspects of the study are unchanged. If data are more variable than a simple model assumes, standard errors and confidence intervals based on that model can be misleading. Over-dispersion is one example: it means the observed variability exceeds what a chosen model expects. Analysts may need a model that accommodates that variability, but the registry record does not report whether over-dispersion was assessed or relevant to the melatonin outcome.

For a continuous endpoint summarized by a mean and standard deviation, the distribution of the data can also affect how well a model’s assumptions fit. The registry record does not report the observed distribution, checks of model assumptions, transformations, or robust alternatives. These are methodological possibilities in general, not documented steps in this trial.

With no reported numerical summaries or inferential analysis, statistical methods cannot be independently evaluated for this endpoint. The registry entries support describing the planned measurement and the general design, but not reconstructing an effect estimate or verifying an analysis.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("LNAA", "Washout", "BH4 (Kuvan)", "BH4 and LNAA")
n   <- c(9, 9, 9, 9)
m   <- c(266.9, 205.7, 220.4, 301.2)
sp  <- c(165.7, 133.1, 138.5, 179.4)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  LNAA  9  266.900  165.700  139.532  394.268
CARM  Washout  9  205.700  133.100  103.390  308.010
CARM  BH4 (Kuvan)  9  220.400  138.500  113.939  326.861
CARM  BH4 and LNAA  9  301.200  179.400  163.301  439.099

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures and records 0 analyses. It identifies serum melatonin at the end of 4 weeks as the primary endpoint, but numerical primary results and statistical tests are not reported in the registry record. Results for the other outcome measures are not reported in the registry record.

Multiplicity arises in general when several outcomes, conditions, time points, or contrasts are tested. The more opportunities there are to declare a result, the greater the chance that at least one apparent finding could arise by chance if each test is interpreted separately. Prespecified priorities and an adjustment strategy can help explain how multiple tests should be interpreted. The registry record does not report a multiplicity plan, a hierarchy among secondary outcomes, or an adjustment for multiple comparisons.

The outcome description mentions measurement every 4 weeks up to 16 weeks and evaluation across four conditions. Multiple observations or condition contrasts can create analytical choices, but the record does not state which time point or contrast was designated for inferential testing beyond the named primary endpoint, nor how other comparisons were handled. Those details are not reported in the registry record.

The primary outcome population is described as participants who completed all phases. The number who completed all phases, the amount of missing outcome data, and the reasons for any missingness are not reported in the registry record. The record does not describe an intention-to-treat population, a per-protocol population, imputation, or a sensitivity analysis for missing measurements. Therefore, the effect of incomplete follow-up on the outcome estimates cannot be assessed.

General statistical principle: excluding participants without complete measurements can change the analyzed group if completion is related to participant characteristics or outcomes. That possibility does not establish that such bias occurred in this study; the relevant details are not reported in the registry record. The difference between the enrollment entry and the arm description further limits clarity about the analyzed population.

12. 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 adverse-event record lists four condition groups: LNAA, washout, BH4 (Kuvan), and BH4 and LNAA. Each group has 9 at risk, with 0 serious adverse events and 0 other adverse events recorded. These are condition-specific entries. They should not be added together to infer a participant total, because the study description says the same group underwent multiple conditions.

A zero count means no event of that category is recorded for the listed group in the registry. It does not establish that the risk is zero, particularly when the record does not provide event definitions, observation details, or numerical safety summaries beyond these counts. The number of deaths is not reported in the registry record.

Because this is a single-group study with participants described under multiple conditions, the entries are not a randomized safety comparison between independent groups. The registry record does not report comparative estimates, uncertainty intervals, or a detailed account of adverse-event collection. The figures therefore describe the recorded counts and at-risk entries, but do not support a precise estimate of relative safety across conditions or rule out uncommon harms.

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

The record establishes that a completed Phase 4, single-group study was designed to assess serum melatonin under washout, LNAA only, Kuvan only, and combined LNAA and Kuvan conditions. It describes the primary measure, units, summary format, and measurement schedule. It also records the investigators’ hypotheses concerning melatonin and urine dopamine.

It does not report the numerical primary-outcome results, the statistical comparisons, or the uncertainty around any effect. Accordingly, readers cannot tell from the registry record whether melatonin values differed across conditions, how large any difference was, or how precisely a difference was estimated. The stated hypotheses are not substitutes for reported findings. Numerical urine dopamine results are also not reported in the registry record.

The study’s single-group structure means the registry does not describe a randomized comparison against a separate control group. Conditions within the same group could be compared using within-person methods in principle, but the record does not report condition order or statistical handling of repeated observations. It therefore does not permit a clear assessment of how temporal changes or condition sequence were addressed.

The enrollment field and arm description give inconsistent group-size entries, while the number who completed all phases is not reported in the registry record. Since the primary endpoint is described for those completing all phases, the size and composition of the analyzed population remain unclear.

These limits mean the record supports an account of the study’s question and design, but not a conclusion about the magnitude, direction, or clinical importance of a treatment effect. It also does not establish that melatonin is a validated surrogate for a clinical outcome. The absence of numerical results in the registry record should not be interpreted as evidence of no effect; it means the effect cannot be evaluated from these entries.

14. Why This Trial Matters Statistically

This study illustrates why a clinical question and a completed study status are not enough to interpret an intervention. The registry identifies a biologically motivated endpoint, describes four conditions in one group, and states hypotheses about melatonin and urine dopamine. Statistical interpretation still requires the outcome values, a defined comparison, and an account of uncertainty. Those results and analysis details are not reported in the registry record.

The within-person structure is statistically important. Comparing measurements from the same participant can be informative, but valid inference depends on recognizing that repeated observations are related and on accounting for timing and condition sequence where appropriate. The registry does not state how the conditions were ordered or how repeated observations were analyzed. A reader therefore cannot determine which statistical comparison would answer the stated question or whether the chosen analysis handled the design.

The difference between the enrollment entry and the arm description is another practical lesson: registry fields can give inconsistent descriptions of the population. The endpoint is limited to participants who completed all phases, but the number completing them is not reported in the registry record. That distinction affects how clearly the analyzed population can be understood.

Finally, the safety counts show why zeros require context. The record reports zero events in each condition entry, but does not provide enough detail to estimate safety precisely or compare conditions. Across efficacy and safety, transparent estimates, uncertainty, analysis populations, and methods are necessary for readers to distinguish an observed result from a hypothesis or a planning assumption.

15. 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 central limitation for interpretation is that numerical results for the primary endpoint are not reported in the registry record. Means and standard deviations for serum melatonin, estimates comparing conditions, and uncertainty measures are absent. Numerical results for urine dopamine are not reported either. This prevents evaluation of the study’s stated hypotheses.

The population count is unclear: enrollment is listed as 10, but the arm description refers to 12 subjects. The record says the primary measure concerns participants who completed all phases, without reporting how many completed those phases. It does not report participant characteristics or how missing measurements were handled.

Design and analysis details are limited. The study is recorded as a single-group study with no allocation and no masking, and the record describes four conditions lasting 4 weeks each. Condition order, statistical methods, repeated-measure handling, period effects, carryover, and sensitivity analyses are not reported in the registry record. No analysis is listed.

The safety entries report at-risk counts and zero serious and other adverse events for each condition, but deaths are not reported in the registry record. Detailed safety methods and uncertainty estimates are also not reported. These entries cannot characterize rare events or provide a controlled comparison.

The sample-size assumptions describe a planning illustration rather than the study’s recorded single-group design. The trial’s own sample-size justification is not reported in the registry record, and the illustration does not supply evidence of observed power. Together, these limitations mean the record documents the study framework more fully than its results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Effects of Kuvan on Melatonin Secretion — NCT01617070.
• Registry record last updated 2016-11-18; status last verified 2016-11.
• Results first posted 2016-11-18.
• 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.

19. Record Summary

The registry identifies a completed Phase 4 study sponsored by the University of Southern California, with a single-group model and no masking. It describes participants with PKU undergoing washout, LNAA only, Kuvan only, and combined LNAA and Kuvan conditions, each lasting 4 weeks.

The primary outcome is serum melatonin at the end of 4 weeks, expressed as a mean and standard deviation in pg/ml. The outcome description refers to measurement every 4 weeks up to 16 weeks and to participants who completed all phases. Enrollment is listed as 10, while the arm description says 12 subjects.

Numerical outcome results, the number completing all phases, and statistical analyses are not reported in the registry record. Safety entries list 9 at risk and zero serious and other adverse events in each condition group; deaths are not reported in the registry record.