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 Initial Experience With a New Laparoscopic Based Robotically Assisted Surgical System for Cholecystectomy (NCT03380572), a non-randomized na study. The primary outcome is Operative Time.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03380572 |
| Phase | NA |
| Condition | Biliary Colic, Cholecystitis |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 40 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Imperial College London |
| Results posted | Yes |
2. Clinical Question
Population
Patients undergoing cholecystectomy in a study that included people with biliary colic or cholecystitis. The registry record reports 40 participants overall, but does not provide further eligibility details or participant characteristics.
Intervention
Cholecystectomy performed using the Senhance surgical robotic system.
Comparator
Cholecystectomy performed using standard laparoscopic instruments.
Primary question
How did operative time, measured in minutes, compare between the Senhance-assisted and standard laparoscopic groups?
The registry describes an initial experience with a new robotically assisted surgical system for cholecystectomy. Its stated primary outcome is operative time, summarized as a median and inter-quartile range over a timeframe of 1 day. The record also lists morbidity data as a secondary outcome.
The registry summary says patients received one of the procedures based on scheduled surgery date. Although that summary uses the word “randomly,” the registry classifies allocation as non-randomized. The groups therefore should not be treated as if the record establishes a randomized comparison. The record describes 20 patients in each group, with the Senhance patients drawn from a prospectively maintained database that was retrospectively examined and compared with a concurrent group.
The central question is descriptive: what operative-time results were recorded, and how much evidence is available to support a comparison? The posted registry record does not report the operative-time values or a statistical analysis of the groups. It therefore does not answer the primary comparison from the information.
3. Trial Design
This completed study enrolled 40 participants and compared two parallel groups: Senhance-assisted cholecystectomy and standard laparoscopic cholecystectomy. The registry lists the allocation as non-randomized and the masking as single. It does not state who was masked or how masking was implemented. The study is listed as having no applicable phase.
The summary describes a prospectively maintained database of the first 20 patients undergoing cholecystectomy with the Senhance system. That database was retrospectively examined and compared with a concurrently treated group of 20 patients who underwent laparoscopic cholecystectomy during the same timeframe. The summary says procedure assignment was based on scheduled surgery date. This is important context: the registry’s non-randomized classification means that the group comparison may reflect differences associated with scheduling or other factors, not only the surgical approach. The record does not report how such factors were assessed or adjusted for.
The study started on 2017-02-10, had a primary completion date of 2017-12-01, and is marked completed. Imperial College London is listed as sponsor. These record details establish the stated setting and status, but do not supply further information about recruitment, eligibility, follow-up, or conduct.
The primary outcome is operative time, measured in minutes and specified as a median with an inter-quartile range. The stated timeframe is 1 day. Morbidity data are listed as a secondary outcome. The registry record lists two outcome measures but no analyses. It does not report the protocol, the sample-size justification, or a detailed statistical analysis plan. The design can therefore be described, but key aspects of how the comparison was planned and evaluated cannot be verified from this 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 | Senhance Cholecystectomy | Laparoscopic Cholecystectomy |
|---|---|---|
| STARTED | 20 | 20 |
| COMPLETED | 20 | 20 |
| NOT COMPLETED | 0 | 0 |
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 | Senhance Cholecystectomy | Laparoscopic Cholecystectomy | Total |
|---|---|---|---|---|
| Participants analysed | 20 | 20 | 40 | |
| Age, Continuous | years | 45.9 (SD 13) | 48.4 (SD 12.2) | 46 (SD 12) |
| Sex: Female, Male: Female | Participants | 17 | 17 | 34 |
| Sex: Female, Male: Male | Participants | 3 | 3 | 6 |
| Race and Ethnicity Not Collected | Participants | — | — | 0 |
| Region of Enrollment: United Kingdom | participants | 20 | 20 | 40 |
6. Primary Endpoint
The registry lists the primary outcome as Operative Time, measured over 1 day.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | minutes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is operative time, measured in minutes. The registry specifies that it is summarized using a median and inter-quartile range, with a timeframe of 1 day. The posted record does not give the observed median or inter-quartile range for either group, define the precise start and stop points for timing, or explain how the endpoint was collected.
In general, operative time is used to describe the duration of a procedure. It can be relevant when evaluating the practical conduct of a surgical approach, but a duration measure alone does not capture every aspect of a procedure or patient experience. Its interpretation depends on a clear definition, consistent measurement, and the clinical and operational context.
In general, the median describes the centre of a distribution, while the inter-quartile range describes the span between its middle portions. These summaries are often useful when a distribution may be skewed or contain unusually long or short times. They do not, by themselves, show the full distribution or establish whether groups differ beyond what might arise from variation in the observed patients.
For this record, the endpoint’s measurement scale and summary format are stated, but its results and the analysis comparing groups are not reported in the registry record. Consequently, readers cannot assess the observed operative-time pattern, its precision, or the size of any group difference from the posted results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record identifies a clear primary outcome—operative time—but does not post the group-specific median or inter-quartile range. It also lists no analyses. As a result, the primary endpoint cannot be interpreted quantitatively from the registry record, and there is no reported estimate or uncertainty interval for a between-group comparison. The endpoint description alone is not a result.
The study includes 20 participants in each group. That describes the recorded group sizes, not the strength of evidence for a difference. Without the outcome values, variability, and an analysis, it is not possible to assess how precisely operative time was estimated or whether the groups’ observed results were similar or different. The registry record does not report a p-value or confidence interval for this endpoint.
The allocation details also constrain interpretation. The registry categorizes the study as non-randomized, while the summary says procedure assignment was based on scheduled surgery date. Non-randomized groups may differ in ways related to the outcome, whether or not those differences are measured. The record does not report group characteristics or adjusted analyses that would help readers judge comparability. The concurrent comparator group is useful context, but does not make the comparison equivalent to a randomized one.
The posted adverse-event counts provide descriptive safety information: no serious adverse events or deaths are listed in either group, and other adverse events are recorded for 3 participants in the Senhance group and 5 in the laparoscopic group. These counts are not a substitute for the primary endpoint analysis, and the registry does not report event descriptions or a formal comparison. They should be read as counts in this study, not as proof that one approach has lower risk.
Any sample-size calculations shown elsewhere on the page are planning illustrations based on an observed effect, not evidence of what the trial was designed to detect or achieved. They are not observed power. The registry record does not report the trial’s own sample-size justification. Without the operative-time results, the reader also cannot independently judge the basis of an effect-based planning illustration from this record.
Overall, the posted information establishes that a small, non-randomized, parallel-group comparison was conducted and identifies its intended primary endpoint. It does not establish the direction or magnitude of the operative-time comparison. Conclusions about that endpoint would require results and methods that are not reported in the registry record.
9. Statistical Methods Explained
The registry record names operative time as the primary outcome and specifies a median and inter-quartile range. It does not report an analysis of that outcome. The explanations below describe general statistical concepts that help interpret this type of study; they are not a description of unreported methods used by the investigators.
Why summarize time with a median and inter-quartile range?
In general, a median is the central value when observations are ordered. The inter-quartile range describes the spread of the middle half of the observations. Together, these summaries can communicate a typical value and a sense of variability without requiring the distribution to be symmetric. A median and inter-quartile range do not reveal every feature of the data, such as the shape of the distribution or unusually extreme observations. A plot or additional summaries can provide complementary information, but the registry record does not report operative-time results.
The choice of summary does not itself specify the comparison method. In general, analyses of two groups can compare distributions, central values, or model-based estimates. The appropriate approach depends on the outcome’s distribution, the study design, and the analysis plan. The registry record does not report which method, if any, was used to compare operative time.
What does a confidence interval convey?
In general, a confidence interval describes the uncertainty around an estimated quantity under the assumptions of the method used to construct it. A narrow interval indicates greater statistical precision than a wide interval, though precision does not remove bias from a non-randomized comparison. An interval for a group contrast would help readers assess which values are compatible with the posted data and analysis. The registry record does not report a confidence interval for operative time.
A p-value, in general, summarizes how compatible observed data are with a specified statistical model and null hypothesis. It does not measure the probability that a treatment effect is true, nor does it describe the practical importance of an effect. A p-value is most informative alongside an estimate, an interval, and a transparent account of the design and analysis. No p-value for the primary outcome is reported in the registry record.
Why does allocation matter?
In general, random allocation can help balance measured and unmeasured characteristics between groups, although it does not guarantee perfect balance in a particular study. Here, the registry labels allocation non-randomized and the summary describes assignment based on scheduled surgery date. The record does not explain the scheduling process or provide enough group characteristics to assess potential differences. A concurrent comparison can help describe experience over the same timeframe, but cannot by itself rule out confounding.
Adjustment for measured factors is one possible way to address some differences in a non-randomized study. Such adjustment depends on which factors were recorded, how they were modeled, and whether the analysis was appropriately specified. The registry record reports no analyses, so it is not possible to say whether adjustment was performed. Nor can readers infer a particular model or covariate set.
How should planning illustrations be read?
In general, sample-size planning asks how many participants may be needed to detect a chosen effect under specified assumptions. The planning illustrations are identified as calculations based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is a stated fraction of the observed effect. These are planning illustrations, not the study’s documented design justification and not observed power. The registry record does not report its own sample-size justification.
The stated convention for the illustrations distinguishes participant counts per arm from total event counts for time-to-event calculations. This study’s primary endpoint is operative time, not a time-to-event endpoint. The registry record does not give primary outcome results or analyses, so these descriptions should not be mistaken for evidence about the trial’s observed precision or findings.
What can the posted counts support?
Counts of adverse events can be reported descriptively, but a formal comparison requires a defined analysis and careful attention to the small group sizes, event definitions, and follow-up. General statistical reasoning cautions against treating a difference in raw counts as a demonstrated difference in underlying risk. The record does not provide event-level detail, a risk estimate, or an inferential analysis. Readers should therefore use the counts as a limited description of what is recorded, rather than as a comparative conclusion.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists two outcome measures: operative time as the primary outcome and morbidity data as a secondary outcome. It does not describe a wider family of planned comparisons, define multiple primary endpoints, or report how multiplicity was addressed. The statistical plan is not reported in the registry record, so it is not possible to determine which comparisons were planned, whether outcome definitions changed, or whether any adjustment for multiple testing was intended.
In general, when many outcomes or comparisons are tested, the chance of finding at least one apparently notable result can increase. Methods to address multiplicity depend on the study aims and analysis plan. This is a general consideration, not a claim that the investigators performed multiple tests. The registry record lists no analyses, so there are no posted inferential results against which to assess this issue.
The record also does not report whether outcome data were missing, how missing observations were handled, or whether participants were excluded from any analysis. The total enrollment and group sizes are stated, but those figures do not show whether all enrolled participants contributed data to each outcome. Missing-data handling and analysis populations are therefore not reported in the registry record.
In general, analysis populations should be defined so that readers know which participants contribute to each estimate. This is particularly relevant when comparing groups in a non-randomized study, where exclusions or incomplete measurements can affect the composition of the groups. The masking designation is listed as single, but who was masked and what role that played in outcome measurement are not reported.
These omissions limit reproducibility and make it difficult to distinguish planned analyses from post hoc analyses. They do not establish that the study had missing data, selective reporting, or multiplicity problems. They mean only that the registry record does not provide enough information to evaluate those possibilities.
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 |
|---|---|---|---|
| Senhance Cholecystectomy | 0 | 20 | 0.0% |
| Laparoscopic Cholecystectomy | 0 | 20 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Senhance Cholecystectomy | 0 of 20 |
| Laparoscopic Cholecystectomy | 0 of 20 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Senhance Cholecystectomy | 3 of 20 |
| Laparoscopic Cholecystectomy | 5 of 20 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Senhance Cholecystectomy | Laparoscopic Cholecystectomy |
|---|---|---|---|
| Wound infection | Skin and subcutaneous tissue disorders | 1 of 20 | 3 of 20 |
| Pain | General disorders | 1 of 20 | 1 of 20 |
| Bile leak | Hepatobiliary disorders | 0 of 20 | 1 of 20 |
| Bleeding | Blood and lymphatic system disorders | 1 of 20 | 0 of 20 |
The posted adverse-event figures list 20 participants at risk for serious adverse events in each group. Serious adverse events affected 0 participants in the Senhance group and 0 in the laparoscopic group. The record also lists 20 participants at risk for other adverse events in each group; other adverse events affected 3 participants in the Senhance group and 5 in the laparoscopic group. Deaths are listed as 0 in both groups.
These are descriptive counts from the registry record. They do not establish that the underlying risks are equal or different, and the record does not provide a statistical comparison or confidence intervals. A zero count means that no event of that category was recorded among the listed participants; it does not show that the risk is absent in other settings or populations.
The record does not provide descriptions, severity breakdowns, timing, duration, or attribution for the other adverse events. It also does not report further detail about how events were collected or followed. The “other” category should not be treated as interchangeable with serious adverse events. Without event-level context and a defined comparative analysis, the counts should not be used to infer a safety advantage for either procedure.
12. What the Result Does, and Does Not, Mean
This record documents a completed comparison of Senhance-assisted and standard laparoscopic cholecystectomy, with 20 participants in each group. It identifies operative time as the primary endpoint and gives a summary format, units, and timeframe. It also records adverse-event counts. These details describe the study and the outcomes it set out to record.
What the posted record does not show is the primary endpoint result. There are no group-specific operative-time medians or inter-quartile ranges, and no reported analysis comparing the groups. Thus, the posted results do not establish whether operative time was shorter, longer, or similar between the groups, nor how precisely any difference was estimated. The endpoint’s name is not a substitute for its observed values.
The non-randomized allocation classification is also important. The summary describes assignment according to scheduled surgery date, but the record does not report enough information to determine how scheduling worked or whether the groups differed in relevant characteristics. Even a reported difference in a non-randomized comparison would need to be interpreted with that limitation in mind; here, the primary results are absent as well.
The serious-event and death counts are zero in both groups, while other adverse events are listed for 3 participants in the Senhance group and 5 in the laparoscopic group. These are limited descriptive data, not proof of equivalence or a comparative safety conclusion. More detail about event types and follow-up is not reported in the registry record.
In general, a study’s result is interpreted by considering the estimate, its uncertainty, the design, outcome definitions, and analysis choices together. In this case, the record supports a description of the study and its posted counts, but not a conclusion about the primary comparison or the relative performance of the procedures. It does not provide a basis for medical advice or for claims about which approach should be used.
13. Why This Trial Matters Statistically
This study is statistically instructive because it illustrates the difference between a registered question and a reported result. The record clearly names operative time as the primary endpoint and specifies its units and summary format. Yet it does not report the endpoint values or an analysis. Knowing what was measured does not tell a reader what was observed.
It also highlights why the design label matters. The registry categorizes allocation as non-randomized, while the summary describes assignment based on scheduled surgery date. Those details should be considered when interpreting any group comparison. A concurrent group offers a reference point, but does not ensure that groups are comparable or eliminate the possibility of confounding.
The adverse-event counts offer another useful statistical lesson: raw counts are not the same as a comparative risk estimate. The registry reports zero serious adverse events and deaths in both groups, along with some other adverse events. Without further event detail or an analysis, those counts describe what was recorded but do not establish a difference or equivalence.
Finally, the record’s lack of reported analyses and sample-size justification shows why transparent methods matter. In general, readers need to know how outcomes were defined, which participants were analyzed, how missing data were handled, and what comparison was planned. Those details help distinguish estimates that address a prespecified question from exploratory findings. Here, several of these details are not reported in the registry record.
The statistical significance of this trial lies in how it teaches careful reading: separate design from results, descriptive counts from inference, and planning calculations from observed evidence. The available record allows a bounded description of the study, but does not supply the information needed to evaluate its primary endpoint comparatively.
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 main limitation for interpreting this trial from the registry record is that the primary endpoint results are not posted. Although operative time is identified as the primary outcome and a median with inter-quartile range is specified, the record gives neither group-specific summaries nor an analysis. The magnitude, direction, and precision of the primary comparison are therefore unavailable.
The non-randomized allocation further limits causal interpretation. The summary says assignment was based on scheduled surgery date, while the registry classifies allocation as non-randomized. The record does not report participant characteristics, details of the scheduling process, or analyses addressing possible group differences. The comparator was concurrent, but that does not establish comparability.
The outcome definition is also limited in the posted record. Operative time is reported in minutes with a timeframe of 1 day, but the record does not explain how timing began and ended, who measured it, or how consistency was ensured. The single-masking designation is not accompanied by an explanation of who was masked.
Although morbidity data are listed as a secondary outcome, the registry record does not provide a detailed description of that measure. Adverse-event counts are available, but event types and other context are not. Missing-data procedures, analysis populations, the statistical plan, and the sample-size justification are not reported in the registry record. The study’s group sizes are known, but cannot by themselves establish whether the study was adequately sized for its intended comparison.
These are limitations of what can be assessed from the posted record; they do not establish that the investigators failed to collect or analyze information elsewhere. They do mean that readers cannot independently verify the primary comparison or evaluate several important aspects of the analysis.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Initial Experience With a New Laparoscopic Based Robotically Assisted Surgical System for Cholecystectomy — NCT03380572.
- Registry record last updated 2019-05-21; status last verified 2019-05.
- Results first posted 2019-05-15.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed, parallel-group, non-randomized study of Senhance-assisted versus standard laparoscopic cholecystectomy. It lists 40 participants, with 20 in each group, and identifies operative time in minutes as the primary outcome, summarized by median and inter-quartile range over a timeframe of 1 day. Morbidity data are listed as a secondary outcome.
The summary describes a retrospective examination of a prospectively maintained database of the first 20 Senhance cases and comparison with a concurrent group of 20 laparoscopic cases. It says procedure assignment was based on scheduled surgery date. The primary endpoint results and analyses are not reported in the registry record.
The posted adverse-event figures list no serious adverse events or deaths in either group. Other adverse events affected 3 participants in the Senhance group and 5 in the laparoscopic group. The record does not provide further event detail or a formal comparison. It also does not report the statistical plan, missing-data handling, analysis populations, or sample-size justification.