Glutamine Therapy for Hemolysis-Associated Pulmonary Hypertension: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Glutamine Therapy for Hemolysis-Associated Pulmonary Hypertension (NCT01048905), a na phase 2 study. The primary outcome is Erythrocyte Glutamine/Glutamate Ratio at 8 Weeks.

2. Clinical Question

The broader study rationale also anticipated changes in markers related to hemolysis, adhesion, arginine bioavailability, endothelial function, and pulmonary hypertension. Those predictions are hypotheses, not findings. The listed secondary outcomes include plasma glutamine, tricuspid regurgitant jet velocity, six-minute walk distance, and liver and renal function tests. The posted results do not give numerical results for these outcomes in the record described.

Statistically, the central question is therefore whether the registry supplies evidence about the primary biomarker endpoint, and how precisely that evidence is estimated. It identifies the endpoint and the number of participants with available blood work, but does not report an endpoint estimate or an inferential analysis. The clinical question can be described from the protocol summary; the effect of treatment cannot be judged from the registry record alone.

3. Trial Design

This was a Phase 2 trial, marked completed in the registry record. The listed start was 2009-03, and the listed primary completion was 2014-03. The sponsor was UCSF Benioff Children's Hospital Oakland. The record gives an enrollment of 13 and describes a single-group model with no masking. Allocation is listed as NA.

The treatment arm was L-glutamine. Its description specifies oral treatment for an 8-week course at 10 grams TID. Because the study is described as single-group, the record does not set out a concurrent untreated or active comparator arm. The design therefore cannot provide a randomized comparison between treatment groups. Any interpretation of change over time would depend on the actual measurement schedule and analysis, neither of which is described in detail in the results record.

The primary endpoint was the erythrocyte glutamine/glutamate ratio at 8 weeks. The record says blood work was available for N=6 participants for this endpoint. That information should not be treated as a statement about the number who received treatment, completed the study, or contributed to every other measure; those analysis populations are not reported in the registry record.

The record lists five secondary outcomes: plasma glutamine; tricuspid regurgitant jet velocity on Doppler echocardiography; six-minute walk distance; liver function tests; and renal function tests. It also identifies six outcome measures overall. Although the trial is marked completed, the record does not report the statistical plan, the timing of measurements for each secondary outcome, or numerical estimates for the primary and secondary outcomes. The registry record includes no analysis records. These omissions limit what can be concluded about the study's results, beyond describing its design and stated aims.

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: Blood work only available for N=6 participants, as reported here.

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 Erythrocyte Glutamine/Glutamate Ratio at 8 Weeks, measured over 8 weeks.

The primary endpoint was the erythrocyte glutamine/glutamate ratio at 8 weeks, measured as a ratio. The record describes it as a novel biomarker of oxidative stress. The study rationale links this biomarker with hemolysis and pulmonary hypertension, and the primary hypothesis was that glutamine supplementation would improve it.

The endpoint is continuous: the record specifies a mean as its summary measure and standard deviation as its measure of dispersion. In general, a mean describes the central value of a continuous measure, while a standard deviation describes how spread out individual measurements are around that mean. These summaries can help readers understand both the average biomarker level and its variability, but they do not by themselves establish a treatment effect.

To interpret a treatment-related change, readers would need the observed endpoint values and a clear description of the relevant comparison, such as whether the analysis compared measurements over time within participants. The registry record does not report the endpoint mean, standard deviation, baseline value, change estimate, confidence interval, or test result. It therefore establishes what was intended to be measured, but not the direction, size, or precision of the observed result.

A biomarker endpoint is not itself a clinical outcome. Even if a change were reported, its meaning for symptoms, function, or pulmonary hypertension would require evidence beyond the biomarker value. The record lists clinical and physiological secondary outcomes, but does not report their numerical results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information that can be interpreted begins with the stated endpoint type and design. The primary measure is a continuous ratio, summarized using a mean and standard deviation. The study is described as single-group, with allocation listed as NA and masking listed as none. The registry record includes no analysis records, and it does not describe the statistical plan. Consequently, the method used to estimate or test the primary result is not reported in the registry record.

What do the mean and standard deviation describe?

In general, the mean is an average that represents the central location of measured values. The standard deviation describes how dispersed the individual observations are around that average. A mean without a measure of uncertainty or dispersion gives an incomplete picture: a similar average can arise from observations that are tightly grouped or widely spread. A standard deviation describes variability among measurements; it is not the same as a confidence interval for the mean or for a treatment effect.

The registry record identifies these summary measures but does not report their values for the primary endpoint. It also does not report a baseline mean, a follow-up mean, or a change estimate. No conclusion about the size or direction of any observed change can be drawn from the endpoint description alone.

What does a single-group design allow?

In general, a single-group study can describe measurements in the group receiving the intervention. If repeated measurements are collected, an analysis may describe change within participants, but the registry record does not specify whether such an analysis was conducted for this endpoint. Without a concurrent comparison group, a before-and-after pattern cannot isolate the effect of treatment from other influences on the measurements. The record does not identify random allocation, and its listed allocation value is NA; it should not be interpreted as a randomized treatment comparison.

Masking is listed as none. In general, masking can reduce the influence of knowledge about treatment assignment on some aspects of measurement or assessment. The registry record does not describe procedures for measurement, assessor roles, or other safeguards, so those details cannot be evaluated from the posted information.

How should uncertainty be understood?

In general, a confidence interval gives a range of values compatible with the data and the method used to calculate it. Its width conveys precision: a wider interval indicates less precise estimation than a narrower interval. A p-value, when reported, addresses how compatible data are with a specified statistical model or null hypothesis; it does not measure the magnitude or clinical importance of an effect. Neither a confidence interval nor a p-value is reported for the primary endpoint in the registry record. No uncertainty estimate can therefore be assessed.

The reported availability of blood work for N=6 participants is relevant because estimates based on fewer observations can be less precise. That general principle does not supply the missing estimate or quantify its uncertainty. The record does not report whether the available observations represent all participants with the relevant measurements, why other blood work was unavailable, or whether any method was used to address missing data.

What do the planning assumptions mean?

The record describes a sample-size planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the illustrated effect to detect is a stated fraction of the observed effect. These are assumptions for a planning illustration, not a description of the trial's single-group design. The registry record does not report the trial's own sample-size justification, and it does not provide the numerical planning results in the information described.

In general, a planning calculation estimates the number of participants that a hypothetical future design might require under specified assumptions. Its output depends on the assumed effect, variability, significance level, allocation, and analysis method. Such an illustration is not observed power and does not establish how likely the completed study was to detect an effect. Because the illustrated design assumes two arms while this study is recorded as single-group, its assumptions should not be mistaken for the trial's actual design.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model assumes. If a model understates variability, standard errors can be too small and inferential results can appear more precise than warranted. This is a general statistical consideration, not a reported feature of this trial. The primary endpoint is described as a continuous ratio, and no model, variance estimate, or analysis result is reported that would show whether over-dispersion was assessed or relevant.

For this record, the most defensible methods interpretation is limited: the endpoint is continuous, the intended summary is a mean with standard deviation, the design is single-group, and the primary endpoint blood-work availability is reported as N=6. The analysis procedure and numerical results are not reported in the registry record. Any more specific account of tests, adjustments, repeated-measures methods, or model assumptions would go beyond what the record states.

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("Treatment: L-glutamine")
n   <- c(6)
m   <- c(2.4)
sp  <- c(1.6)
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  Treatment: L-glutamine  6  2.400  1.600  0.721  4.079

11. Multiplicity, Missing Data and Analysis Populations

The registry record identifies six outcome measures. The primary outcome is the erythrocyte glutamine/glutamate ratio at 8 weeks; listed secondary outcomes include plasma glutamine, tricuspid regurgitant jet velocity on Doppler echocardiography, six-minute walk distance, and liver and renal function tests. The record does not report how many hypotheses were tested or whether a multiplicity procedure was used.

In general, evaluating several outcomes can increase the chance that at least one result appears notable by chance if each is tested separately. Approaches to multiplicity may adjust thresholds or otherwise account for the family of tests. No such approach is reported in the registry record, and the record includes no analysis records. It is therefore not possible to determine how the several stated outcomes were handled statistically.

For the primary endpoint, the record says blood work was available for N=6 participants. It does not report the number with missing measurements for each outcome, reasons for unavailable data, or whether the available endpoint observations were analyzed as a complete-case subset. It also does not describe imputation, sensitivity analyses, or another missing-data method. These procedures are not reported in the registry record.

The definitions of analysis populations are also not reported. The enrollment figure does not establish how many participants contributed to each outcome analysis, and the primary endpoint's blood-work availability should not be generalized to the secondary outcomes. Readers cannot determine from the registry record whether analyses followed an intention-to-treat approach, included only participants with measurements, or used another population definition.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pain (23.1%), acute chest syndrome (7.7%), sepsis (7.7%).

For the L-glutamine group, the registry reports 13 participants at risk for serious adverse events and 4 affected. It reports 13 at risk for other adverse events and 1 affected. The record also reports 1 death. These are the registry's safety counts; the record does not give the timing, duration of observation, event-level detail, or relationship of events to treatment.

The listed serious adverse event terms are Pain (23.1%), Acute Chest Syndrome (7.7%), and Sepsis (7.7%). These terms and percentages describe the registry's reported serious-event information. They do not establish that L-glutamine caused the events. The record does not provide a separate comparison group that could support a comparative safety estimate, and it does not report an attribution assessment or the definitions used for event coding.

The death count should be read as a reported safety count, not as evidence about cause. The registry record does not state the cause of death or whether it was considered related to treatment. Counts and percentages alone also do not show the severity or clinical course of each event. The available information supports a descriptive account of reported events, not a causal conclusion about safety.

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

The record describes a Phase 2, single-group study of oral L-glutamine for patients with sickle cell disease or thalassemia and pulmonary hypertension. Its primary question concerns the erythrocyte glutamine/glutamate ratio at 8 weeks, a biomarker selected in relation to oxidative stress. The registry record does not report a numerical result for that endpoint, so it does not establish whether the ratio changed, in which direction, or with what precision.

That absence of an endpoint estimate should not be interpreted as evidence of no change. It means the posted information is insufficient to evaluate the result. The record also does not report numerical findings for the listed secondary outcomes, so the stated hypotheses about hemolysis, endothelial function, pulmonary hypertension, and clinical endpoints remain hypotheses in this account.

Even if a biomarker result were available, it would not by itself establish a change in symptoms, function, or clinical outcomes. Biomarkers can be useful for studying biological pathways, but their interpretation depends on the measured effect, its uncertainty, and evidence connecting the biomarker to outcomes that matter clinically. The registry lists physiological and functional secondary measures, but their results are not reported in the record described.

The study's single-group design also limits causal interpretation. Without a concurrent comparison group, observed changes cannot be separated confidently from changes that might occur over time or from other influences. The record does not describe the primary analysis, missing-data handling, or analysis populations, adding uncertainty about how the endpoint data were evaluated.

The appropriate conclusion is therefore about the limits of the posted evidence: the registry record identifies the intervention, intended population, endpoint, and some safety counts, but does not provide a numerical primary result or enough analysis detail to assess treatment-related change. It does not support a claim that treatment worked or did not work.

14. Why This Trial Matters Statistically

This trial is statistically interesting because it connects a biological hypothesis to a defined continuous endpoint. The erythrocyte glutamine/glutamate ratio was selected as a biomarker of oxidative stress, with the study rationale linking that pathway to hemolysis and pulmonary hypertension. Specifying a measurable endpoint makes the hypothesis testable, but interpreting it still requires the observed values, variability, and analysis method. Those results are not reported in the registry record.

The study also illustrates why design matters as much as endpoint choice. Its single-group structure can describe the treated group, but it does not provide a randomized comparison with a control group. A change in a biomarker, if reported, would need cautious interpretation because the design alone cannot rule out other explanations for change over time.

Availability of blood work for N=6 participants is an important feature of the record. It highlights the need to distinguish the full enrollment from the population contributing to a specific endpoint. Without an estimate and uncertainty measure, readers cannot evaluate how precisely the primary biomarker was characterized. Without information on missingness and the analysis population, they cannot judge how the available endpoint data relate to the broader enrolled group.

Finally, the record lists several secondary outcomes alongside the primary biomarker. This makes the statistical handling of multiple outcomes relevant, but the analysis records and multiplicity approach are not reported. The trial therefore serves as a useful example of how a registry can communicate a research question and design while leaving key elements needed for quantitative interpretation unavailable.

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.

Several limitations specific to this trial constrain interpretation of the registry record. The study is described as single-group, with allocation listed as NA and masking listed as none. There is no separate control group identified, so the record does not support a randomized between-group estimate. The registry record does not describe whether baseline measurements were compared with follow-up measurements or how any change was analyzed.

The primary endpoint is identified, but its numerical result is not reported. Although the record specifies a mean and standard deviation, neither value is given. No estimate of change, confidence interval, or test result is reported. Blood work for the primary endpoint was available for N=6 participants, but the record does not explain why other blood work was unavailable or how the resulting observations were handled.

The registry lists six outcome measures, yet includes no analysis records. It does not report a statistical analysis plan, a multiplicity procedure, definitions of analysis populations, or missing-data methods. The secondary outcomes are named, but their numerical results are not reported in the record described. The safety information is also limited: the record gives event counts and selected terms, but does not report timing, cause of death, treatment attribution, or event-level descriptions.

The planning illustration is not the trial's own design justification. It assumes equal allocation between two arms and a normal approximation, whereas the trial is described as single-group. The registry record does not report the trial's sample-size justification. Together, these limitations mean the design and aims can be described, but the magnitude, precision, and causal interpretation of the primary endpoint cannot be assessed from the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Glutamine Therapy for Hemolysis-Associated Pulmonary Hypertension — NCT01048905.
• Registry record last updated 2021-06-10; status last verified 2021-06.
• Results first posted 2021-06-10.
• 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 record describes NCT01048905, a completed Phase 2, single-group trial sponsored by UCSF Benioff Children's Hospital Oakland. It lists an enrollment of 13, a start of 2009-03, and primary completion in 2014-03. The intervention was oral L-glutamine for an 8-week course at 10 grams TID. Masking is listed as none and allocation as NA.

The primary endpoint was the erythrocyte glutamine/glutamate ratio at 8 weeks, summarized in the record as a mean with standard deviation. Blood work for this endpoint was available for N=6 participants. The registry record does not report the primary endpoint result, its uncertainty, or numerical results for the listed secondary outcomes. It includes no analysis records.

The safety record reports serious and other adverse event counts for the L-glutamine group and 1 death, without enough detail to determine causation. Overall, the registry documents the trial's question and design but does not provide the outcome estimates needed to judge the size or precision of the primary biomarker result.