A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria (NCT03095885), a na na study. The primary outcome is Percent of Oxalate Absorption Normalized by Baseline Urinary Oxalate Excretion Over a 24 Hour Test Period.

2. Clinical Question

3. Trial Design

This completed study is identified as NCT03095885 and is titled A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria. The registry records an enrollment of 22 and classifies the model as SINGLE GROUP. The intervention is a controlled oxalate-rich test meal. There is no described parallel control arm, and the record identifies allocation as NA and masking as NONE. These features make the study a within-participant measurement exercise rather than a randomized comparison of treatments.

The listed phase is NA. The study start is recorded as 2016-11, with primary completion in 2017-01, and its status is COMPLETED. All enrolled subjects are included in the stated primary-outcome population. The record does not report additional details about eligibility, participant characteristics, meal composition, recruitment, adherence, or the handling of measurements that were unavailable or unusable.

The stated aim is to identify individuals with greater absorption of oxalate by examining an increase in urinary oxalate excretion after the controlled meal. The primary endpoint is a continuous percentage measure normalized by baseline urinary oxalate excretion over a 24-hour test period. The registry also lists percent of oxalate absorption by test interval and percent change from baseline for the urinary oxalate-to-creatinine ratio by test interval as secondary outcomes. Outcome estimates and analysis results are not reported in the registry record. The statistical analysis plan, including any model used for repeated test intervals, is also not reported.

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

Analysis population for the primary outcome, as defined in the registry: Enrolled set which included all enrolled subjects

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 Percent of Oxalate Absorption Normalized by Baseline Urinary Oxalate Excretion Over a 24 Hour Test Period, measured over 24 hours during baseline and test day following oxalate-rich meal.

The primary endpoint is titled percent of oxalate absorption normalized by baseline urinary oxalate excretion over a 24-hour test period. Its stated timeframe is 24 hours during baseline and the test day following the oxalate-rich meal. The registry defines the measure as 100*[UOx/test - UOx/baseline]/Ox intake from the test meal. In other words, the calculation uses the difference between test-day and baseline urinary oxalate, scaled by the oxalate intake from the meal and expressed as a percentage.

This continuous measure is intended to characterize the urinary response to a controlled oxalate challenge in the study population. Baseline normalization makes the participant’s baseline urinary excretion part of the endpoint calculation; it does not create a separate control group or establish a causal treatment contrast. The registry describes the outcome statistic as a mean with standard deviation, but the observed mean and standard deviation are not reported in the registry record.

The endpoint is used to address the stated pilot-study aim of identifying individuals with greater absorption based on increased urinary oxalate excretion after the meal. The endpoint definition alone does not show the size or distribution of any observed response. Those quantities, along with details needed to assess measurement and interpretation, are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, and the registry identifies its summary statistic as a mean with standard deviation. A mean condenses the measured values into an average on the endpoint’s scale. It can be useful for describing the typical response of the enrolled set, but it does not show how values are distributed or whether a small number of unusual observations influence the average. The standard deviation describes the spread of values around the mean. It is not the same as uncertainty in the mean: the former describes variation among observations, while a confidence interval for the mean would express uncertainty about the estimated average under a specified method.

No primary mean, standard deviation, or confidence interval is reported in the registry record. Thus, the measure’s planned form can be described, but its observed level and variability cannot. A statistical test or interval cannot be reconstructed from the endpoint title and formula alone. Doing so would require outcome data or summary statistics that are not reported.

What does the endpoint calculation represent?

The registry defines the primary measure as 100*[UOx/test - UOx/baseline]/Ox intake from the test meal. The numerator represents the change from baseline in urinary oxalate, and the denominator scales that change by the meal’s oxalate intake. Multiplying by 100 expresses the resulting quantity as a percentage. The endpoint is described as percent of oxalate absorption normalized by baseline urinary oxalate excretion. That name and formula define the intended summary; they do not substitute for reported participant results or demonstrate how accurately the measure reflects absorption in practice.

Baseline normalization can help express a response relative to a participant’s baseline measure, but it also means the calculated endpoint depends on both the test and baseline measurements. Measurement error or unusual values in either component can affect the resulting value. The registry does not report details about assay procedures, measurement precision, handling of extreme values, or any sensitivity analysis. Without those details and the observed values, the extent of any such influence cannot be assessed.

Why does the single-group structure matter?

The study is classified as SINGLE GROUP, with allocation recorded as NA and masking as NONE. Participants received the test meal, and the primary outcome uses baseline and test-day information. This structure can describe a response associated with the meal challenge in the enrolled set. It does not by itself separate the response from other influences that could affect measurements over time. A baseline reference is not equivalent to a concurrently observed comparison group, and a before-and-after calculation should not be read as a randomized treatment effect.

The registry does not report a statistical model for repeated observations, an adjustment strategy, or a plan for accounting for participant-level characteristics. These details matter if multiple test intervals or repeated measurements contribute to analysis. The secondary outcome titles refer to test intervals, but the interval schedule and the methods used to combine or compare those measurements are not reported in the registry record.

What would over-dispersion mean in general?

In general, over-dispersion means that observed variability is greater than a statistical model expects. It can make standard errors too small and uncertainty appear less than it is if the model fails to account for the extra variability. This concept is relevant when selecting and checking models for outcomes with a particular distribution. The primary endpoint in this study is described as continuous and summarized with a mean and standard deviation; the registry does not report a model or evidence of over-dispersion. It would therefore be inappropriate to assert that over-dispersion occurred or that a particular correction was used.

What can a confidence interval add?

In general, a confidence interval presents a range of values compatible with an estimate under the method’s assumptions. Its width reflects precision: a narrower interval indicates less statistical uncertainty around the estimate than a wider interval, though neither width alone establishes the measurement’s practical meaning. A confidence interval does not guarantee that the underlying assumptions are correct, nor does it remove limitations of a single-group design. No confidence interval for the primary measure is reported in the registry record, so its precision cannot be assessed from the registered outcome information.

The registry lists 3 outcome measures and 0 analyses. The primary outcome is described as a mean of a continuous measure, but there are no posted analysis results in the record to interpret. The statistical analysis plan, estimation method, missing-data approach, and any adjustment for repeated intervals are not reported in the registry record. These omissions prevent readers from determining which inferential procedures, if any, were applied to the outcomes.

The registry’s sample-size note describes planning illustrations based on an observed effect, with 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. Such illustrations are planning calculations, not observed power and not a description of the actual single-group study design. They do not supply the missing primary estimate or establish that the study was designed around a particular inferential target.

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("Test Meal")
n   <- c(22)
m   <- c(2.84)
sp  <- c(2.36)
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  Test Meal  22  2.840  2.360  1.794  3.886

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures: the primary normalized percentage of oxalate absorption over the 24-hour test period, percent of oxalate absorption by test interval, and percent change from baseline for the urinary oxalate-to-creatinine ratio by test interval. Multiple outcomes and interval-specific measurements can create multiple opportunities to examine patterns. In general, multiplicity adjustments or a prespecified hierarchy can help control how repeated statistical testing affects the interpretation of evidence. The statistical analysis plan and any multiplicity strategy are not reported in the registry record, so it is not possible to determine whether adjustment was planned or used.

The registry records 0 analyses. It does not report estimates, test statistics, p-values, confidence intervals, or interval-specific findings for the outcomes. The primary outcome specifies an enrolled-set population, including all enrolled subjects, but the record does not explain whether every enrolled participant contributed a usable measurement or how missing observations were handled. Reasons for missingness, imputation, exclusions, and sensitivity analyses are not reported in the registry record.

These gaps affect interpretation in different ways. Missing-data methods can influence estimates when measurements are unavailable, while multiplicity methods affect how evidence from several outcomes or repeated intervals is assessed. Neither issue can be resolved from outcome definitions alone. The record also does not report a detailed analysis population beyond the stated enrolled set, so it is unclear how the intended population related to any analyzed observations. Conclusions about the completeness, robustness, or statistical significance of the outcome findings cannot be drawn from the registry information.

12. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports safety figures for the Test Meal group. For serious adverse events, 22 participants were at risk and 0 were affected; the reported number of deaths was 0. For other adverse events, 22 participants were at risk and 3 were affected. These counts describe the safety information recorded for this group. The registry lists no top serious adverse-event terms.

Counts at risk identify the group to which the event figures refer; they do not provide detail about event timing, duration, severity within the other-event category, or whether events were considered related to the test meal. The record does not report those details. The count of 0 affected by serious adverse events means none were recorded in that category for this group in the registry entry. It does not establish that the meal has no risks or that an event could not occur in other settings.

These are descriptive safety figures from a single-group pilot study, not a comparison between groups. Without a comparator, event counts cannot show whether the observed events were more or less frequent than they would have been under another condition. The figures should be read as the registry’s recorded counts, not as a causal assessment or a complete account of safety.

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

The record documents a pilot study designed to examine urinary oxalate response after a controlled oxalate-rich test meal. Its primary outcome is a normalized percentage measure using baseline and test-day urinary oxalate and meal oxalate intake. The registry identifies the enrolled set as the primary-outcome population and describes the outcome as a mean with standard deviation. This information clarifies what the investigators intended to measure, but the observed primary result is not reported in the registry record.

Without the estimate and its variability, the posted information does not establish the average response, the spread of responses, or the precision of any estimate. It also does not show whether individual responses differed meaningfully, how any greater-absorption classification was defined, or whether the endpoint behaved consistently across test intervals. Those questions require results and analysis details that are not reported.

The single-group design is suited to describing a meal-associated measurement in the enrolled set, but it does not furnish a randomized treatment contrast. Baseline normalization does not change that design feature. Consequently, a change from baseline should not be interpreted as the isolated causal effect of the meal without an appropriate comparison and supporting assumptions. The registry does not report such a comparison.

The study’s completed status and enrollment of 22 provide context about the recorded study, but they do not replace outcome evidence. The safety counts are also descriptive and do not establish comparative risk. Overall, the record permits a clear account of the research aim, intervention, endpoint definition, and design, while leaving the main empirical result and its uncertainty unavailable.

14. Why This Trial Matters Statistically

This study is statistically notable because it turns a controlled meal challenge into a continuous response measure. The endpoint combines test-day and baseline urinary oxalate with the meal’s oxalate intake, aiming to express the response as a normalized percentage. That construction makes the measurement question explicit: the interest is not simply the test-day value, but the change relative to baseline in relation to the challenge.

The single-group structure is also important. It suits a pilot investigation focused on characterizing response to a test meal, but it does not support a direct randomized contrast with an untreated or alternative-meal group. A within-participant baseline reference may be informative for description, yet it does not provide the same inferential protection as a concurrent comparison. Recognizing that distinction prevents the endpoint from being misread as a treatment-effect estimate.

The outcome list also illustrates why analysis plans matter. The registry includes a primary measure and secondary measures by test interval, but reports 0 analyses. When outcomes span repeated intervals, clear definitions of the analysis population, missing-data handling, and any multiplicity strategy help readers understand how the evidence was generated. Those details are not reported in the registry record.

Finally, the record demonstrates the difference between documenting a measurement plan and reporting evidence from that measurement. The primary outcome is defined, and the study is marked completed, but the numerical result and its precision are not reported. Statistical interpretation therefore depends on separating what the design set out to measure from what the registry actually reports.

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 main trial-specific limitation in the registry information is the absence of the primary outcome result. Although the endpoint is defined and the summary statistic is specified as a mean with standard deviation, neither value is reported in the registry record. No confidence interval or other estimate of precision is reported. The primary research question therefore cannot be answered from the posted outcome information.

The study has a SINGLE GROUP model and no described parallel comparator. The baseline value used in the endpoint formula is a reference measurement, not a concurrent control arm. This means the design cannot directly distinguish a meal-associated response from other influences on the measurements. The record does not report a causal comparison or an analysis intended to support one.

Further interpretation is constrained by unreported methodological detail. Eligibility criteria, participant characteristics, meal composition, measurement procedures, interval definitions, and handling of missing or extreme values are not reported in the registry record. The statistical analysis plan, including any model for repeated intervals or multiplicity adjustment, is also not reported. The registry lists 3 outcome measures and 0 analyses, leaving no outcome-level results to evaluate against the planned definitions.

The safety information is limited to event counts for the Test Meal group. The registry does not report event descriptions beyond the absence of listed top serious terms, nor does it provide a comparator for safety interpretation. These limitations are specific to what the record reports; they do not establish that the underlying study lacked additional procedures or documentation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria — NCT03095885.
• Registry record last updated 2021-10-28; status last verified 2021-10.
• Results first posted 2020-03-24.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT03095885 is a completed single-group pilot study titled A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria. The registry records an enrollment of 22, a controlled oxalate-rich test meal, allocation NA, masking NONE, and phase NA. The study start is recorded as 2016-11 and primary completion as 2017-01.

The primary outcome is a continuous, normalized percentage measure of oxalate absorption over a 24-hour test period, summarized as a mean with standard deviation. The registry also lists 2 secondary outcome types concerning absorption and urinary oxalate-to-creatinine ratio by test interval. It records 3 outcome measures and 0 analyses. The primary numerical result, its variability, and the statistical analysis plan are not reported in the registry record.

Safety figures list 0 serious adverse events among 22 at risk, 3 other adverse events among 22 at risk, and 0 deaths. These counts are descriptive and come from a single-group study.