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 Hepatic Effects of Gastric Bypass Surgery (NCT00701376), a na na study. The primary outcome is Aspartate Transaminase (AST) Change.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00701376 |
| Phase | NA |
| Condition | Liver Diseases |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 106 |
| Arms in the primary outcome | n/a |
| Lead sponsor | The Cleveland Clinic |
| Results posted | Yes |
2. Clinical Question
The study asks whether liver function changes after gastric bypass surgery in people described in the registry as having liver disease in the setting of morbid obesity. Its primary focus is change in aspartate transaminase (AST), comparing measurements before surgery with measurements taken when participants had lost 60% of their preoperative excess weight or when weight loss had plateaued. The registry describes the primary outcome as the post-procedure value minus the pre-procedure value.
The clinical question is therefore about within-person change over time, rather than a difference between a surgery group and a concurrent untreated or alternative-treatment group. Although the condition is recorded as Liver Diseases, the eligibility criteria and the extent to which every enrolled participant had pre-existing liver disease are not reported in the registry record. The record describes participants undergoing laparoscopic gastric surgery and liver tissue being biopsied during surgery and again at the later assessment. The intervention field lists liver biopsy.
AST is one measure used to assess liver function, and the registry also lists diagnostic-accuracy outcomes for other laboratory or test measures, including ALT, ALK, total bilirubin, PT, PTT, ICG k value, and albumin. These additional measures do not change the primary question, which is specifically about AST change. The registry record does not report a numerical AST change, its direction, or its precision. It also does not report the results for the other listed outcomes in the registry record for this analysis. The study therefore frames a relevant longitudinal question, but the posted information does not establish the size or statistical uncertainty of the observed change.
3. Trial Design
NCT00701376 is recorded as completed, with a start date of 2008-06 and primary completion date of 2014-02. The sponsor is The Cleveland Clinic, and enrollment is listed as 106. The study model is single group; allocation is recorded as NA, and masking is recorded as NONE. The phase field is recorded as NA. The record classifies the study kind as other.
The design description concerns participants undergoing laparoscopic gastric surgery. Liver tissue obtained during surgery is to be compared with tissue obtained after participants reached 60% loss of their preoperative excess weight or after weight loss had plateaued. This is a before-and-after framework: the same participant is the reference for the comparison across the two time points. The registry lists liver biopsy as the intervention, while its arm description explains the paired tissue assessments in the setting of gastric surgery.
There is no randomized comparison group identified. The registry explicitly notes that this is not a randomized comparison and that the arms are not a like-for-like control comparison. The single-group structure means the primary contrast is not a treatment-versus-control estimate. Changes over time may be described within the study group, but this design alone does not separate changes associated with surgery from other changes that occur over the same period.
The registry lists 21 outcome measures and 10 analyses. It names AST change as the primary outcome and includes secondary diagnostic-accuracy outcomes for several liver-related tests. The record does not report the detailed analysis plan, eligibility criteria, follow-up completion distribution, or the exact schedule and criteria for determining when a participant reached the later assessment. Those details should not be inferred from the brief design description.
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 | Roux-en-Y Gastric Bypass (RYGB) |
|---|---|
| STARTED | 106 |
| COMPLETED | 105 |
| NOT COMPLETED | 1 |
Analysis population for the primary outcome, as defined in the registry: 84 patients did not have AST measured after the surgery
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 | Roux-en-Y Gastric Bypass (RYGB) |
|---|---|---|
| Participants analysed | 106 | |
| Age, Continuous | years | 46 (SD 11) |
| Sex: Female, Male: Female | Participants | 70 |
| Sex: Female, Male: Male | Participants | 31 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 90 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 16 |
| Body Mass Index (BMI) | kg/m^2 | 48 (SD 8) |
| Obesity Level: Morbid Obesity | Participants | 93 |
| Obesity Level: Severe Obesity | Participants | 11 |
| Obesity Level: Other | Participants | 2 |
| Duration of Obesity | years | 26 (SD 12) |
6. Primary Endpoint
The registry lists the primary outcome as Aspartate Transaminase (AST) Change, measured over from before surgery to the time when they lost 60% of their preoperative excess weight or weight loss had plateaued after this procedure.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 99.8% Confidence Interval |
| Unit | U/L |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is change in aspartate transaminase (AST), measured in U/L. The registry defines the comparison as the value after the procedure minus the value before the procedure. The later measurement was intended to occur when participants had lost 60% of their preoperative excess weight or when weight loss had plateaued. Thus, the endpoint is a within-participant change rather than a comparison between separate treatment groups.
AST is an enzyme measured in blood and used as one indicator in evaluating liver status. In general, examining change from baseline can describe whether a measured value shifted over follow-up, while accounting for the fact that measurements come from the same person. That makes the endpoint relevant to the study's question about liver-related changes after surgery. It does not, by itself, establish a change in liver tissue or explain why a laboratory value changed.
The registry specifies a 99.8% confidence interval as the dispersion measure for this endpoint. A confidence interval, in general, expresses the statistical uncertainty around an estimated quantity under the method used to calculate it. However, the numerical AST estimate and its confidence interval are not reported in the registry record. The record states that 84 patients did not have AST measured after surgery. It does not report the analysis population used for the endpoint or how missing post-surgery measurements were handled.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies AST change as the primary outcome but does not report a numerical estimate of that change, its direction, or its 99.8% confidence interval. A conclusion about the size or precision of the primary result therefore cannot be drawn from the posted information. The absence of a reported estimate is not evidence that the change was zero, and it does not establish that AST increased or decreased.
The outcome definition is a difference within participants: the later AST value minus the pre-surgery value. In general, a positive difference under that definition would indicate a higher measured value at the later assessment, while a negative difference would indicate a lower value. This is an explanation of the sign convention, not a description of the study's observed result, which is not reported in the registry record.
The planned follow-up point was tied to weight loss progress: the time at which a participant lost 60% of preoperative excess weight or weight loss plateaued. Because follow-up is defined by these milestones rather than by a single fixed interval in the endpoint description, the timing could vary across participants. The actual timing distribution is not reported in the registry record. It is therefore not possible to determine from the endpoint description how long participants were followed individually or whether variation in timing affected the estimates.
The record states that 84 patients did not have AST measured after surgery. This substantial missing-outcome information matters because a before-and-after estimate requires relevant measurements at both time points, or an analysis method that addresses missing follow-up data. The number of participants included in the primary analysis, reasons for missing measurements, and approach to missingness are not reported in the registry record. The reported enrollment of 106 does not, by itself, establish the denominator used for the AST estimate.
The design is single group, with no randomized comparator. Any observed before-and-after difference would describe change over time among participants with the relevant measurements; it would not by itself identify the effect of surgery apart from other influences. The registry record also does not report a numerical estimate for the secondary outcomes. Consequently, the posted information supports describing the question and design, but not a quantitative judgment about the results or their uncertainty.
9. Statistical Methods Explained
The primary analysis is framed as a paired comparison. Each participant's AST before surgery is compared with that participant's later AST, and the stated direction is later value minus earlier value. In general, paired analysis uses the within-person differences rather than treating measurements from the same person as independent observations. This can be useful because each participant serves as their own reference, but it does not remove the possibility of changes over time unrelated to the procedure.
What does the confidence interval describe?
The registry specifies a 99.8% confidence interval for the mean AST change. In general, a confidence interval is a range calculated from data using a statistical method; it describes uncertainty around an estimate under the method's assumptions. A narrower interval indicates greater precision than a wider interval, all else being equal. The interval does not show the range of individual participants' changes, and it does not by itself indicate whether a change is clinically important.
The actual mean change and interval limits are not reported in the registry record. The record also does not state the exact confidence-interval calculation method, assumptions about the distribution of paired differences, or whether the reported interval was adjusted for multiple outcomes or analyses. Those methodological details should not be inferred from the stated confidence level alone.
Why do paired measurements matter?
Measurements from the same participant are generally related. A paired method accounts for that relationship by analyzing each participant's change. In general, an analysis that instead treats pre-surgery and post-surgery observations as unrelated may misrepresent the uncertainty. The registry's description of the endpoint indicates a before-and-after comparison, but does not give enough information to verify the model or computational details used for the analysis.
Participants without a post-surgery AST measurement cannot contribute a complete paired change unless a statistical method supplies or otherwise addresses the missing value. The record says 84 patients did not have AST measured after surgery. It does not report whether those participants were excluded, whether another method was used, or how missingness was assessed. No specific missing-data assumptions can therefore be attributed to the analysis.
How should the planning illustration be understood?
The registry describes sample-size calculations as planning illustrations based on an observed effect, not as the trial's original design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. These are calculation assumptions, not evidence that the study itself used a two-arm randomized design. The registry describes the study model as single group and allocation as NA.
The record's description of the illustration distinguishes participant counts per arm from total event counts for time-to-event calculations. No calculated sample-size values are reported in the record details addressed. Even when such planning counts are available, they are hypothetical planning quantities; they are not observed power and do not establish the certainty of a trial result. The observed AST effect needed to interpret an effect-based illustration is also not reported in the registry record.
Why can over-dispersion matter?
In general, over-dispersion means that observed variability is greater than a statistical model expects. If a model assumes less variability than the data contain, uncertainty can be understated and statistical evidence can appear stronger than it is. This is a general issue in statistical modeling, not a reported feature of this study. The registry record does not identify an over-dispersion assessment or describe a model for count outcomes.
For the AST endpoint, interpretation depends on the distribution of within-person changes and the method used to estimate their uncertainty. Neither the distribution nor a diagnostic assessment is reported in the registry record. The confidence-interval label alone does not reveal whether the analysis used a normal approximation, a robust method, or another approach.
What can be learned from the analysis description?
The record gives the endpoint, unit, comparison direction, follow-up definition, and confidence-interval level. These details clarify what the primary result was intended to estimate. They do not provide the estimate itself, a test statistic, a p-value, or a complete analysis plan. In general, an estimate describes magnitude, an interval describes precision, and a test result addresses compatibility with a specified null hypothesis under its assumptions. None should be substituted for another, and the missing numerical result prevents quantitative interpretation.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 21 outcome measures and 10 analyses. AST change is identified as the primary outcome; secondary outcomes include diagnostic-accuracy measures for AST, ALT, ALK, total bilirubin, PT, PTT, ICG k value, and albumin. The exact relationship between the listed outcome measures and analyses is not reported in the registry record. Nor does the record state whether multiplicity was addressed through an adjustment, a hierarchy of hypotheses, or another strategy.
In general, examining multiple outcomes or analyses can increase the chance of finding at least one apparently notable result by chance if each is interpreted separately. This is why a prespecified primary outcome and a clearly described multiplicity strategy can help readers distinguish confirmatory from exploratory findings. The registry names a primary endpoint, but the analysis plan and any multiplicity procedure are not reported in the registry record. Numerical results for the listed secondary outcomes are not reported in the record details addressed.
For missing data, the record explicitly states that 84 patients did not have AST measured after surgery. It does not give reasons for these missing measurements, report the number with complete paired AST values, or describe how missing outcomes were handled. It also does not state whether missingness was examined in relation to participant characteristics or earlier measurements. Without those details, the potential influence of missing follow-up data on the endpoint estimate cannot be assessed.
The analysis population is not reported in the registry record. Enrollment is listed as 106, but that number should not be taken as the denominator for the primary analysis without a reported analysis population. The record also does not specify whether participants were analyzed according to a prespecified rule or whether any other exclusions occurred.
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 |
|---|---|---|---|
| Liver Function | 2 | 106 | 1.9% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Liver Function | 2 of 106 |
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 |
|---|---|
| Liver Function | 0 of 106 |
Most frequent serious adverse event terms
| Event term | Organ system | Liver Function |
|---|---|---|
| Death | Cardiac disorders | 2 of 106 |
| pulmonary embolism, | Blood and lymphatic system disorders | 2 of 106 |
| Bowel obstruction | Gastrointestinal disorders | 1 of 106 |
Serious events with the highest arm-level rate: death (1.9%), pulmonary embolism, (1.9%), bowel obstruction (0.9%).
The registry reports a Liver Function group with 106 participants at risk for serious adverse events and 2 affected. It reports 106 at risk for other adverse events and 0 affected, and lists 2 deaths. The record's top serious adverse-event terms are Death (1.9%), pulmonary embolism (1.9%), and Bowel obstruction (0.9%). These are the registry's reported figures and terms; they are not a substitute for a full event-level account.
The listed percentages are not enough to determine whether terms refer to distinct participants or overlapping events. The registry record does not provide event narratives, timing, severity details beyond the serious-event grouping, or an assessment of whether events were related to surgery. It also does not provide comparative safety data from a control group. Because this is a single-group study, the posted figures describe reported events in that group and do not establish how the event experience compares with another approach.
Deaths are reported, but the record does not provide further details about their causes or timing in the registry record for this analysis. The listed serious-event terms should be read as reported safety information, not as evidence about causation.
12. What the Result Does, and Does Not, Mean
The registry record defines a study intended to examine liver-related changes after gastric bypass surgery, with AST change as the primary endpoint. It gives the unit, the direction of the comparison, and the intended later assessment point. It also reports that 84 patients did not have AST measured after surgery. These details describe the research question and an important limitation in the availability of the primary outcome.
The numerical primary result is not reported in the registry record. Without the estimated AST change and its 99.8% confidence interval, the magnitude, direction, and precision of the result cannot be evaluated. The same limitation applies to the secondary outcomes: their names are listed, but their numerical findings are not reported in the registry record for this analysis. It would be inappropriate to infer either benefit or lack of benefit from the absence of numerical results.
Even if a within-person change estimate were available, the single-group design would place limits on its interpretation. In general, a change observed between two time points can reflect the studied procedure, other changes during follow-up, or a combination of influences. Without a like-for-like control group, the design cannot isolate a causal effect by comparison with what would have happened to similar participants without the procedure or with another treatment.
The follow-up point is defined by participants' weight-loss progress rather than a single fixed time in the endpoint description. The actual follow-up timing and analysis population are not reported in the registry record. Missing post-surgery AST measurements and the lack of information on how they were handled add uncertainty about the representativeness of any complete-case result. The study record is therefore informative about the intended measurement and design, but the posted information does not support a quantitative conclusion about the AST result or a causal conclusion about surgery.
13. Why This Trial Matters Statistically
This trial matters statistically because it illustrates the difference between a well-defined question and a fully interpretable numerical result. The registry specifies a within-person AST change, the measurement unit, the subtraction direction, and a 99.8% confidence interval as the dispersion measure. Those details allow readers to understand the target quantity. But because the numerical estimate and interval are not reported in the registry record, readers cannot assess the observed magnitude or precision.
The design also makes the comparison structure important. Participants are compared with their own earlier measurements, not with a randomized control group. In general, paired measurements can be useful for describing change, while a concurrent comparator is important for distinguishing change associated with an intervention from change over time or from other influences. The record's single-group model and allocation field make that distinction central to interpretation.
Missing outcome information is another key statistical issue. The record states that 84 patients lacked a post-surgery AST measurement. Missingness affects more than the nominal enrollment count: it raises questions about how many complete pairs contributed to the primary estimate and whether those participants represent the full enrolled group. The analysis population, reasons for missing measurements, and handling strategy are not reported in the registry record.
Finally, the registry lists multiple outcomes and analyses. In general, a clear distinction between a primary endpoint and additional analyses helps readers understand which results were intended to answer the main question and how to interpret secondary findings. The record names a primary outcome but does not report the detailed analysis plan or a multiplicity strategy. Together, these features show why statistical interpretation depends on the endpoint, comparison design, missing-data approach, and reporting of estimates—not simply on the fact that a study was completed.
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.
The central limitation for interpreting this record is that the numerical AST result is not reported. Although the registry identifies a mean change and a 99.8% confidence interval, it does not give the estimate or interval limits. The direction and precision of the primary result therefore cannot be described. Numerical results for the listed secondary outcomes are also not reported in the registry record for this analysis.
The record states that 84 patients did not have AST measured after surgery. It does not report why measurements were missing, how many participants had complete before-and-after data, or what method was used to address missingness. These omissions prevent assessment of whether the analyzed participants could differ systematically from those without follow-up measurements.
The single-group design has no randomized comparator. A before-and-after comparison can describe change over time, but it does not by itself separate effects associated with surgery from other influences. The follow-up assessment is based on reaching 60% loss of preoperative excess weight or a plateau in weight loss; the distribution of assessment times and the criteria used to define a plateau are not reported in the registry record.
Further details that would support interpretation are also absent: eligibility criteria, participant characteristics, the full statistical analysis plan, the analysis population, and any approach to multiplicity are not reported in the registry record. The record lists 21 outcome measures and 10 analyses, but does not explain the relationship among them. Safety figures are reported without event-level details or causal assessments. These limitations constrain what can be concluded from the posted information without implying that unreported methods or results were absent from the study itself.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Hepatic Effects of Gastric Bypass Surgery — NCT00701376.
- Registry record last updated 2020-06-19; status last verified 2020-06.
- Results first posted 2020-06-19.
- 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
NCT00701376, titled “Hepatic Effects of Gastric Bypass Surgery,” is recorded as completed. The sponsor is The Cleveland Clinic; enrollment is 106, the start date is 2008-06, and the primary completion date is 2014-02. The registry describes a single-group study with allocation recorded as NA and masking as NONE.
The primary endpoint is mean AST change in U/L, defined as the later measurement minus the pre-surgery measurement. The later assessment was intended at 60% loss of preoperative excess weight or after weight loss plateaued. The registry specifies a 99.8% confidence interval but does not report the numerical estimate or interval limits. It states that 84 patients did not have AST measured after surgery.
The record lists 21 outcome measures and 10 analyses, along with serious adverse-event information. The numerical primary result, analysis population, missing-data handling, and detailed statistical plan are not reported in the registry record.