This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Recombinant Human Growth Hormone During Rehabilitation From Traumatic Brain Injury. (NCT00766038), a randomized phase 2 study. The primary outcome is Functional Outcome 6 Months After Injury, as Measured by the Processing Speed Index.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00766038 |
| Phase | Phase 2 |
| Condition | Traumatic Brain Injury |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 63 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of Pennsylvania |
| Results posted | Yes |
2. Clinical Question
Population
People recovering from traumatic brain injury during rehabilitation. The registry record does not report detailed eligibility criteria or a fuller description of the analyzed population.
Intervention
Recombinant human growth hormone (rhGH). The study summary describes treatment beginning 1 month after traumatic brain injury and continuing for 6 months.
Comparator
Placebo treatment, with placebo doses adjusted monthly according to the arm description.
Primary question
Does rhGH treatment during the subacute period after traumatic brain injury improve functional outcome 6 months after injury, measured by the Processing Speed Index?
The clinical question reflects the study’s stated primary hypothesis. The summary explains that growth hormone deficiency has been considered in people after traumatic brain injury, while also noting that there is no accepted gold standard for diagnosing it in this population. The study also describes insulin-like growth factor-1 as relevant to the somatotropic axis and as a neurotrophic agent. These points provide the rationale recorded by the study; they do not establish that participants were selected for treatment on the basis of a specific growth hormone deficiency test.
The registry lists additional questions about methods for diagnosing growth hormone deficiency and the relationship between growth hormone deficiency or insufficiency and functional recovery. Those are secondary topics, distinct from the primary comparison of functional outcome. The primary endpoint is specifically the Processing Speed Index at 6 months after injury, rather than a general measure of every aspect of recovery. The record also lists processing speed at 1 year after injury among secondary outcomes.
The posted primary results give a median score of 82.5 in each arm. That is a description of the observed group summaries, not by itself an estimate of the uncertainty around the treatment contrast or a test of the primary hypothesis.
3. Trial Design
The registry identifies this as a phase II, randomized, parallel-group trial comparing recombinant human growth hormone with placebo. Enrollment was 63. The posted primary outcome groups contain 31 participants in the rhGH arm and 32 in the placebo arm. The registry status is completed; the recorded study start is 2008-09 and primary completion is 2013-06.
The study summary describes the trial as randomized, double-blind, and placebo-controlled. The registry’s masking classification is quadruple. These descriptions indicate that the record reports masking, but it does not specify in the available information which roles were masked or how masking was maintained and assessed. The placebo arm description says that doses were adjusted monthly to maintain blinding. The rhGH arm description reports a starting dose of 400 microgramsg/day and monthly dose adjustments, but the recorded text is truncated, so the complete dosing plan cannot be established from the registry record.
The primary outcome was measured 6 months after injury. The study summary describes treatment as starting 1 month after traumatic brain injury and continuing for 6 months. This describes the planned intervention period in the summary; the registry record does not give participant-level treatment exposure or adherence information.
The record lists five secondary outcomes and six outcome measures. These include IGF-1 levels, processing speed at 1 year after injury, growth hormone response to L-arginine stimulation at baseline, and rates of diabetes mellitus, arthralgias, or peripheral edema. The record does not provide a detailed statistical analysis plan, the randomization procedure, allocation concealment methods, or definitions of analysis populations. The registry record also contains no analysis entries, which does not establish that no analyses were conducted; it means that analysis details are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Active Treatment With Recombinant Human Growth Hormone | Placebo Treatment |
|---|---|---|
| STARTED | 31 | 32 |
| COMPLETED | 16 | 18 |
| NOT COMPLETED | 15 | 14 |
Reasons for not completing this period:
| Reason | Active Treatment With Recombinant Human Growth Hormone | Placebo Treatment |
|---|---|---|
| Lost to Follow-up | 15 | 14 |
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.
| Characteristic | Unit | Treatment With Recombinant Human Growth Hormone | Placebo Treatment | Total |
|---|---|---|---|---|
| Participants analysed | 31 | 32 | 63 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 31 | 32 | 63 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 32.2 (SD 15.2) | 30.1 (SD 13.7) | 31.1 (SD 14.3) |
| Sex: Female, Male: Female | Participants | 14 | 15 | 29 |
| Sex: Female, Male: Male | Participants | 17 | 17 | 34 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 4 | 4 | 8 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 27 | 28 | 55 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 3 | 2 | 5 |
| Race (NIH/OMB): White | Participants | 28 | 30 | 58 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | Participants | 31 | 32 | 63 |
| Baseline IGF-1 level < 1 SD below expected mean | Participants | 3 | 3 | 6 |
| Baseline L-Arginine stimulation test | ng/mL | 2.2 (0.6 to 5.9) | 1.2 (0.5 to 5.7) | 1.3 (0.5 to 5.8) |
6. Primary Endpoint
The registry lists the primary outcome as Functional Outcome 6 Months After Injury, as Measured by the Processing Speed Index, measured over 6 months.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | Processing speed index standardized scor |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is functional outcome 6 months after injury, measured with the Processing Speed Index. The record describes this as an age-standardized score. Higher scores represent better functioning and lower scores represent poorer function. The description gives 100 as the mean of a normative population, with 110 and 90 corresponding to one standard deviation above and below normal, and 120 and 80 corresponding to two standard deviations above and below normal.
Processing speed is a specific aspect of cognitive functioning. In this trial, it provides a defined outcome for comparing the rhGH and placebo groups at a specified time after injury. A standardized score can help place an individual or group result in relation to a normative reference, but it does not describe every dimension of recovery after traumatic brain injury.
The registry reports the endpoint as a median with an inter-quartile range. The rhGH group median is 82.5, with an inter-quartile range from 73.0 to 96.0. The placebo group median is also 82.5, with an inter-quartile range from 79.0 to 99.0. An inter-quartile range describes the middle portion of the observed score distribution; it is not a confidence interval for the median or for the difference between groups.
The score’s direction is important when reading the results: larger values correspond to better functioning on this measure. However, the two medians alone do not show how uncertain the between-group contrast is, whether an adjusted comparison was performed, or whether the observed distributions differ in ways not captured by their medians.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary outcome has a median Processing Speed Index of 82.5 in the rhGH treatment arm and 82.5 in the placebo arm. The reported inter-quartile ranges are 73.0 to 96.0 for rhGH and 79.0 to 99.0 for placebo. These summaries describe the distributions of scores in the posted groups. They do not provide a direct estimate of the treatment effect with uncertainty.
The identical medians mean that the central score reported for each group is the same at the precision shown. They do not establish that the full score distributions are the same. The inter-quartile ranges differ, and group medians do not reveal the shape of either distribution, the influence of individual observations, or the degree of overlap between participants’ scores.
The endpoint description states that higher scores represent better functioning. It also provides normative reference values, including 100 as the mean of a normative population. Those reference points help interpret the scale, but they are not a randomized comparison and do not tell whether a difference between treatment groups is statistically or clinically important. The registry record does not report a confidence interval, p-value, adjusted treatment estimate, or other inferential result for the primary comparison. It therefore does not report the precision of a treatment-effect estimate or the result of a formal test of the primary hypothesis.
The arm sizes for the posted primary outcome are 31 for rhGH and 32 for placebo, within a total enrollment of 63. The record does not state whether these are all randomized participants with outcome data, whether any participants were excluded from the endpoint analysis, or how missing scores were handled. The difference between enrollment and an analysis population cannot be characterized without those details.
Randomization is intended to support a fair comparison between treatment groups, but a reader also needs information about the analysis and uncertainty to assess what the observed summaries can establish. The registry record does not report the randomization procedure, adjustment factors, analysis population, or a detailed primary analysis method. It is therefore appropriate to describe the posted values as group summaries, not as proof for or against a treatment effect.
The record includes secondary outcomes, but their presence does not substitute for a reported primary comparison. The statistical plan, multiplicity procedure, and analysis results for those outcomes are not reported in the registry record. No conclusion about the secondary findings can be drawn from the outcome names alone. Likewise, the safety counts are descriptive event summaries and do not establish a causal safety difference between arms.
Overall, the registry’s primary result gives a useful description of the observed Processing Speed Index scores. It does not provide the uncertainty or inferential analysis needed to quantify how compatible the results are with different treatment effects. The posted values should be interpreted at that descriptive level.
9. Statistical Methods Explained
The reported endpoint and trial structure determine what can be said statistically. This study is recorded as randomized and parallel-group, with rhGH and placebo arms. Randomization is generally used to make treatment groups comparable in expectation, while a parallel-group design assigns participants to one group for comparison with another. These are general features of trial design; the registry record does not describe the specific randomization procedure or allocation concealment.
What does a median describe?
A median is the central value of an ordered set of observations: half the observed values lie at or below it and half at or above it, subject to ties. It is often useful when a distribution may be skewed or when a typical value is better represented by the center than by an arithmetic average. The registry reports the median Processing Speed Index as 82.5 for each arm. A median is a group summary, not an estimate of the difference between groups by itself.
The inter-quartile range describes the spread of the middle portion of the observed values, between the first and third quartiles. The recorded ranges are 73.0 to 96.0 for rhGH and 79.0 to 99.0 for placebo. These ranges describe score variability within each arm. They should not be read as confidence intervals: they do not directly express uncertainty about a median or a treatment contrast.
How does a treatment comparison differ from group summaries?
A treatment comparison ordinarily estimates a contrast between the groups and describes its uncertainty. Depending on the prespecified plan and data, that could involve an unadjusted or adjusted estimate with a confidence interval, or a hypothesis test. A confidence interval is a general statistical tool that conveys the range of effect estimates compatible with the data under the method’s assumptions. A p-value, when reported, describes how surprising data at least as inconsistent with a null hypothesis would be under that hypothesis and the specified model. Neither can be recovered from the two medians and inter-quartile ranges alone.
The registry record does not report a confidence interval or p-value for this primary outcome, nor does it state a model or adjustment strategy. The posted primary result is consequently descriptive. It would be inappropriate to infer statistical significance from the fact that the medians are equal, or to treat the inter-quartile ranges as uncertainty intervals for the treatment effect.
Why does the outcome scale matter?
The Processing Speed Index is reported as an age-standardized score, with higher scores indicating better functioning. The registry description sets 100 as the mean of a normative population and gives reference points for scores above and below that mean. A standardized score makes the result interpretable relative to that reference, but the scale description does not determine what size of between-group difference would matter to participants or clinicians. The record does not report a threshold for a clinically important difference.
Because the endpoint is reported with medians and inter-quartile ranges, distributional information is relevant. In general, over-dispersion means that observed variation is greater than a statistical model expects. When that occurs, standard errors and confidence intervals based on an unsuitable variance model can be misleading. The registry record does not identify a model for this endpoint, so there is no basis to say whether over-dispersion was assessed or whether any particular method was used.
What can safety counts tell us?
Adverse event counts and denominators describe how many participants were reported to have events in each arm. They do not, by themselves, account for timing, severity beyond the recorded categories, exposure duration, or uncertainty in comparisons. A serious adverse event is a distinct recorded category from other adverse events in the registry summary. Counts are informative descriptions, but causal interpretation requires the trial’s definitions, ascertainment procedures, and comparative analysis. Those details are not reported in the registry record.
What do sample-size illustrations mean?
Any planning illustrations based on an observed effect are hypothetical calculations for future-study planning under stated assumptions. They are not observed results and are not observed power for the completed trial. Observed power is not a substitute for an effect estimate and its uncertainty. The registry record does not report the trial’s original sample-size justification or the assumptions used when planning enrollment.
More generally, a statistical result depends on the endpoint definition, the population included in the analysis, the missing-data approach, and the model or test. Those details can affect the interpretation even when the group summaries are unchanged. The available record reports the primary endpoint summaries and arm sizes, but does not report enough analysis detail to reconstruct or validate an inferential comparison.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists five secondary outcomes and six outcome measures, in addition to identifying the primary Processing Speed Index outcome. When a study considers multiple outcomes or multiple analyses, the chance of obtaining at least one apparently notable result can increase. A prespecified multiplicity strategy may address that issue, for example by defining a testing order or adjusting inference. The registry record does not report whether a multiplicity procedure was planned or used, how primary and secondary hypotheses were prioritized for testing, or whether the listed secondary outcomes were analyzed.
The registry record contains no analysis entries. This does not mean that no statistical analyses occurred; it means that analysis details are not reported in the registry record. The record also does not provide a statistical analysis plan, details of any interim analyses, or a statement about whether the endpoint analysis was prespecified as an intention-to-treat, per-protocol, or other analysis.
Missing-data handling is not reported in the registry record. The posted endpoint groups include 31 participants in the rhGH arm and 32 in the placebo arm, while total enrollment was 63. The record does not explain whether every enrolled participant contributed an endpoint score, whether any scores were missing, how missing values were handled, or whether any participants were excluded from the analysis. It also does not report sensitivity analyses for missing data.
These omissions matter because the analysis population and missing-data assumptions help define what the estimated result represents. Without them, the posted group summaries can be described, but it is not possible to determine whether they reflect all randomized participants or a subset, or how robust the results would be to alternative missing-data assumptions.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Recombinant Human Growth Hormone | 2 | 31 | 6.5% |
| Placebo Treatment | 2 | 32 | 6.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Recombinant Human Growth Hormone | 0 of 31 |
| Placebo Treatment | 0 of 32 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 2% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Recombinant Human Growth Hormone | 12 of 31 |
| Placebo Treatment | 15 of 32 |
Most frequent serious adverse event terms
| Event term | Organ system | Recombinant Human Growth Hormone | Placebo Treatment |
|---|---|---|---|
| seizure | Nervous system disorders | 2 of 31 | 2 of 32 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Recombinant Human Growth Hormone | Placebo Treatment |
|---|---|---|---|
| Elective Surgery | General disorders | 6 of 31 | 4 of 32 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 2 of 31 | 6 of 32 |
| Myalgia | Musculoskeletal and connective tissue disorders | 1 of 31 | 6 of 32 |
| Headache | Nervous system disorders | 1 of 31 | 3 of 32 |
| Dry mouth | General disorders | 1 of 31 | 3 of 32 |
| Drowsiness | Nervous system disorders | 1 of 31 | 1 of 32 |
Serious events with the highest arm-level rate: seizure (6.5%).
The safety summary reports serious adverse events in 2 of 31 participants in the rhGH arm and 2 of 32 participants in the placebo arm. It reports other adverse events in 12 of 31 participants receiving rhGH and 15 of 32 receiving placebo. Deaths are reported as 0 in each arm. The most frequent serious adverse-event term listed is seizure, at 6.5%.
These figures are descriptive counts from the registry record. They do not show when events occurred, whether participants experienced more than one event, how events were judged to be related to treatment, or how long participants were exposed. The record does not report the event definitions, ascertainment procedures, or a statistical comparison of safety outcomes. The term seizure at 6.5% is the registry’s listed serious-event term and percentage; it should not be interpreted as a comparative risk estimate.
Similar serious-event counts do not establish equivalent safety, and differences in other-event counts do not establish a treatment-caused difference. Such conclusions require an appropriate comparative analysis and adequate information about event collection and participant exposure, which are not reported in the registry record. The counts describe what the registry posted, not an individual participant’s risk or a basis for medical decisions.
12. What the Result Does, and Does Not, Mean
The result means that the registry reports the same median Processing Speed Index, 82.5, in both the rhGH and placebo groups at the primary assessment time of 6 months after injury. It also reports the inter-quartile ranges for each group, which describe the middle spread of observed scores. The endpoint scale is oriented so that higher scores indicate better functioning.
The result does not establish that the treatments have identical effects. Equal medians can occur even when the distributions differ, and the registry does not report a direct estimate of the between-group effect or its uncertainty. Without an inferential comparison, the posted summaries do not show whether the data are compatible with a range of treatment effects, including effects in either direction.
The result also does not establish whether any difference would be clinically important. The registry record does not provide a clinically important difference threshold for the Processing Speed Index. Its normative reference values help explain the scale, but they do not define a threshold for a meaningful treatment benefit.
Nor can the posted primary endpoint alone summarize all aspects of recovery after traumatic brain injury. It measures processing speed at a specified time, while the record lists other secondary outcomes, including processing speed at 1 year after injury, IGF-1 levels, and growth hormone response to stimulation. The names of those outcomes do not establish what their results were.
The safety counts likewise describe reported events rather than proving a safety difference or absence of one. The record reports no deaths in either arm, but it does not supply enough information to characterize all possible harms or compare event rates inferentially.
In short, the posted primary result is a pair of descriptive group summaries. It is not, on its own, a formal test of the stated hypothesis, a precise estimate of treatment effect, or a conclusion about clinical benefit or harm. Those interpretations would require analysis and reporting details that are not reported in the registry record.
13. Why This Trial Matters Statistically
This trial raises a clear statistical question: how should a randomized comparison be interpreted when the registry posts endpoint summaries but not an inferential treatment estimate? The trial is recorded as randomized and placebo-controlled, with a defined primary measure and time point. Those features establish the intended comparison, while the reported medians and inter-quartile ranges provide a descriptive view of the primary outcome.
The distinction between description and inference is central. The identical reported medians are straightforward to communicate, but do not quantify uncertainty about the treatment contrast. Inter-quartile ranges characterize score spread within arms; they are not substitutes for confidence intervals around a contrast. Readers need the estimate, its uncertainty, the analysis population, and the method used to interpret a randomized comparison to assess the primary hypothesis fully.
The record also illustrates why endpoint selection and scale interpretation matter. Processing Speed Index is a specific functional measure, and its direction and normative reference are stated. That clarity helps readers understand what higher or lower values mean. At the same time, a single endpoint cannot represent every dimension of recovery, and the record’s additional outcomes raise questions about how multiple outcomes were prioritized and interpreted. The multiplicity approach is not reported.
Finally, the safety counts show why event totals need context. Denominators are given, but details about event timing, participant exposure, ascertainment, and comparative analysis are not. Statistical interpretation depends not only on numbers but also on how outcomes were defined and how participants entered the analysis.
The registry record is therefore useful for identifying the trial question, design, primary endpoint, posted summaries, and selected safety counts. Its limitations also show why transparent reporting of analysis methods, uncertainty, and missing-data handling is essential to interpreting a clinical trial.
14. 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 trial-specific limitations in interpretation arise from what the registry record does not report. The primary result is given as medians and inter-quartile ranges, without a treatment-effect estimate, confidence interval, or p-value. The record therefore does not show the precision of the primary comparison or the result of a formal hypothesis test.
The statistical analysis plan is not reported in the registry record. The record does not specify the primary analysis model, whether covariates were used, the analysis population, or how the primary endpoint was handled analytically. It also does not explain whether the posted outcome denominators represent all randomized participants with available data or a selected analysis population.
Missing-data methods are not reported. The record does not describe the amount or pattern of missing primary outcome data, reasons for missingness, imputation methods, or sensitivity analyses. The extent to which the posted summaries might be affected by incomplete outcome data cannot therefore be assessed.
The trial’s sample-size justification is not reported in the registry record. Nor are details of interim analyses or the multiplicity approach for the listed secondary outcomes. The registry lists five secondary outcomes and six outcome measures, but does not provide a statistical plan for interpreting them together.
The masking classification is quadruple, while the study summary describes the trial as double-blind. The record does not explain which roles were masked or the operational details of masking. The rhGH arm description is truncated, limiting interpretation of the full dosing plan. Finally, safety reporting lacks details on event definitions, timing, exposure, and treatment attribution. These limitations do not invalidate the reported summaries, but they restrict what conclusions can be drawn from them.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Recombinant Human Growth Hormone During Rehabilitation From Traumatic Brain Injury. — NCT00766038.
- Registry record last updated 2019-11-18; status last verified 2019-11.
- Results first posted 2019-11-18.
- 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.
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18. Record Summary
The registry identifies a completed phase II randomized parallel-group trial of recombinant human growth hormone versus placebo during rehabilitation after traumatic brain injury. Total enrollment was 63. The study summary describes treatment starting 1 month after injury and continuing for 6 months.
The primary outcome was the Processing Speed Index at 6 months after injury, reported as a median with an inter-quartile range. The rhGH arm had a median of 82.5 and an inter-quartile range of 73.0 to 96.0; the placebo arm also had a median of 82.5, with an inter-quartile range of 79.0 to 99.0. Higher scores indicate better functioning. The registry record does not report an inferential comparison for this endpoint.
The record lists five secondary outcomes and reports selected adverse-event counts, including 2 participants with serious adverse events in each arm and 0 deaths in each arm. Analysis methods, missing-data handling, multiplicity procedures, and the original sample-size justification are not reported in the registry record.