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 BULLET: Bladder Ultrasound Limits Length (of Time), Expedites Treatment (NCT03860311), a randomized na study. The primary outcome is Time to Successful Completion of Pelvic Ultrasound.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03860311 |
| Phase | NA |
| Condition | Point-of-Care Bladder Ultrasound, Urethral Catheter |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 45 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of Alabama at Birmingham |
| Results posted | Yes |
2. Clinical Question
Population
Patients presenting to a pediatric emergency department with abdominal or pelvic complaints. The registry record does not report further eligibility details or a more specific analysis population.
Intervention
Point-of-care bladder ultrasound. The bladder was scanned upon enrollment and, unless already full at the initial scan, scanned again every 30 minutes.
Comparator
Standard care using a urethral bladder catheter to allow retrograde filling of the bladder.
Primary question
How much time elapses from placement of the order to completion of pelvic ultrasound images, comparing the bladder-ultrasound approach with urethral catheterization?
The trial’s stated aim was to compare time to successful completion of pelvic ultrasound. The brief summary describes success as full visualization of the uterus and ovaries. The primary endpoint is time from order placement to the point when pelvic ultrasound images are completed, with a stated timeframe from baseline to 180 minutes.
This is a comparison of two ways to prepare the bladder for imaging, not a comparison of diagnostic accuracy or subsequent clinical outcomes. The registry also lists pain measured by the Verbal Numerical Rating Scale as a secondary outcome. The posted results include the primary time outcome, but the registry record does not report a secondary-outcome result or a comparative statistical test. The question can therefore be framed from the trial’s design, while the posted results offer only group-specific summaries for the primary outcome.
3. Trial Design
BULLET (NCT03860311) is recorded as a randomized, parallel-group study with no masking. The registry lists an enrollment of 45 and a completed status. The study start date is 2019-07-20, and the primary completion date is 2021-05-01. The phase is listed as NA. The sponsor is the University of Alabama at Birmingham.
Participants were assigned to a bladder-ultrasound group or a standard-of-care group. In the ultrasound group, point-of-care bladder ultrasound was performed upon enrollment. Repeat scans were planned every 30 minutes unless the initial scan indicated that the bladder was full. In the standard-of-care group, a urethral catheter was placed to fill the bladder retrogradely. The registry describes the study as comparing the time to successful completion of pelvic ultrasound between these approaches.
The primary measure is continuous: time in minutes from order placement to completion of pelvic ultrasound images. Its stated timeframe is baseline to 180 minutes. The registry posts group means and 95% confidence intervals, rather than a reported treatment contrast or a test of the difference between groups. The recorded analysis count is zero. As a result, the posted group summaries should not be mistaken for a reported inferential comparison.
The registry lists pain measured by the Verbal Numerical Rating Scale as a secondary outcome. It does not post a result for that outcome. Further operational details, including eligibility criteria, randomization procedures, allocation concealment, and the intended analysis population, are not reported in the registry record. The design description supports understanding the assigned approaches and endpoint, but does not establish details beyond those explicitly recorded.
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 | Bladder Ultrasound | Standard of Care |
|---|---|---|
| STARTED | 22 | 23 |
| COMPLETED | 22 | 23 |
| 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 | Bladder Ultrasound | Standard of Care | Total |
|---|---|---|---|---|
| Participants analysed | 22 | 23 | 45 | |
| Age, Continuous | years | 15.33 (SD 1.98) | 14.7 (SD 2.183) | 15.00 (SD 2.091) |
| Sex: Female, Male: Female | Participants | 22 | 23 | 45 |
| Sex: Female, Male: Male | 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 | 7 | 5 | 12 |
| Race (NIH/OMB): White | Participants | 14 | 17 | 31 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 | 1 | 2 |
| Region of Enrollment: United States | participants | 22 | 23 | 45 |
6. Primary Endpoint
The registry lists the primary outcome as Time to Successful Completion of Pelvic Ultrasound, measured over Baseline to 180 minutes.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | minutes |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is time to successful completion of pelvic ultrasound, measured in minutes. The registry defines the interval as beginning when the order is placed and ending when the pelvic ultrasound images are completed. The stated timeframe is baseline to 180 minutes. The brief summary describes successful completion as full visualization of the uterus and ovaries.
As a general statistical point, a time-based process endpoint can capture how long it takes to reach a specified procedural milestone. It is distinct from a measure of diagnostic accuracy, patient experience, or a later health outcome. Here, the endpoint is relevant to the trial’s stated comparison because the two assigned approaches are different ways of preparing the bladder before imaging.
The posted results summarize the endpoint using a mean and a 95% confidence interval for each group. A mean describes the average observed time in that group; it does not show the distribution of individual times or whether every participant reached the milestone within the stated timeframe. The registry record does not report a detailed endpoint definition beyond the order-to-image-completion interval and the summary’s description of successful visualization. It also does not report how participants without a completed scan, if any, were handled.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted mean time was 104.0 minutes in the Bladder Ultrasound group (95% confidence interval 82.64 to 125.3) and 92.82 minutes in the Standard of Care group (95% confidence interval 80.29 to 105.3). These are group-specific estimates. The registry does not report a between-group estimate, confidence interval for a contrast, or hypothesis test, so the posted results do not quantify the uncertainty around the difference between assigned approaches.
A confidence interval describes uncertainty around an estimate under the statistical method used to construct it. It is not a range containing every individual participant’s time, nor does it establish that the true group mean must lie inside the interval. The intervals for the two group means overlap. That observation alone is not a formal test of the difference between means: a direct comparison would require an estimate and uncertainty measure for the contrast, or another prespecified analysis. Neither is reported in the registry record.
The group sizes were 22 for Bladder Ultrasound and 23 for Standard of Care. Those counts describe the posted result groups, but the registry does not explain the analysis population or how missing or incomplete endpoint observations were addressed. The enrollment is 45. The record does not state whether all enrolled participants contributed to the posted means.
The record marks the study completed and reports the means with confidence intervals, but records no analyses. It also indicates that values for a two-arm continuous-endpoint comparison are missing or not estimable. Consequently, the descriptive summaries should not be read as a sponsor-reported test of superiority, equivalence, or non-inferiority. No such conclusion can be drawn from the reported group means alone.
The outcome concerns time to completion, not pain, image quality beyond the stated successful-visualization criterion, or downstream care. Pain was listed as a secondary measure, but its result is not reported in the registry record. The posted primary summaries therefore address only the average timing information they contain. They do not show participant-level variation, the frequency of very long times, or whether the process differed for particular patient subgroups.
In practical reading, the means are estimates of average time in the two groups, and the intervals indicate that those estimates are imprecise. The available information does not support a definitive comparative claim. A reported contrast with its uncertainty, along with details on the analysis population and endpoint handling, would be needed to interpret the comparative effect more fully.
9. Statistical Methods Explained
The primary endpoint is continuous, and its reported parameter is the mean. A mean is the arithmetic average of observed values in a group. In this trial, each value represents time from order placement to completion of pelvic ultrasound images. A mean is an accessible summary, but it can conceal variation: participants may have had similar times or a wide range of times, and the group mean alone does not reveal which pattern occurred.
What do the confidence intervals express?
The registry reports a 95% confidence interval for each group mean. In general, a confidence interval expresses the precision of an estimate under the assumptions of the method used to construct it. A narrower interval indicates greater precision than a wider interval, while the interval’s location indicates the values most compatible with the estimate under that method. The intervals do not describe the spread of individual participant times. The registry does not identify the specific calculation method or assumptions used for these intervals.
The Bladder Ultrasound mean is 104.0 minutes, with a 95% confidence interval from 82.64 to 125.3. The Standard of Care mean is 92.82 minutes, with a 95% confidence interval from 80.29 to 105.3. These intervals apply separately to the group means. They are not a confidence interval for the difference between group means. Comparing two separate intervals by eye is not a substitute for estimating the between-group contrast and its uncertainty.
Why is a direct comparison important?
Randomization is intended to support a fair comparison of assigned groups, but the numerical comparison still needs an appropriate analysis. For continuous outcomes, an analysis may estimate a difference in means, with an interval that describes uncertainty in that difference. The registry record does not report such an estimate, interval, or test. It records zero analyses and notes that values for a two-arm comparison of the continuous endpoint are missing or not estimable. The posted means therefore remain descriptive summaries, not a reported inferential result.
As a general statistical point, the choice of analysis can depend on the distribution of the outcome, the estimand of interest, and how incomplete observations are handled. Time measurements may have asymmetry or unusually long observations; a mean can be sensitive to such values. The registry does not report participant-level data, a distributional summary, an adjustment strategy, or an alternative analysis. It is therefore not possible to assess those features from the posted summaries.
What role does the sample-size illustration play?
The registry’s sample-size assumptions describe a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The illustration is not the trial’s own design justification. The registry record does not report the protocol’s sample-size justification, the target effect used when planning enrollment, or a planned power calculation. No numerical sample-size illustration results are reported in the record. Such planning figures, where available, would be hypothetical participants-per-arm requirements under stated assumptions, not observed power and not evidence about the trial’s result.
As a general point, power is a design property tied to assumptions about the effect, variability, allocation, and analysis. Calculating a value after observing the data does not establish how likely the trial was to detect an effect under its actual design. The illustration described in the registry is explicitly based on the observed effect and should not be treated as the trial’s original planning analysis.
How should the endpoint timeframe be read?
The stated timeframe is baseline to 180 minutes, while the endpoint definition describes the interval from order placement until the images are completed. The record does not explain how times beyond the stated timeframe, or participants without a completed scan during that period, were treated. It also does not report whether the analysis used the mean among all randomized participants, only participants with completed scans, or another population. These details matter because excluding or handling incomplete observations differently can change the meaning of a group mean.
More generally, statistical interpretation depends on transparent definitions of the population, outcome, and analysis. The registry provides the assigned procedures, the timing definition, group sizes, means, and confidence intervals. It does not provide the direct comparison or enough methodological detail to reconstruct it. Accordingly, interpretation should stay at the level of the posted group summaries and avoid treating an unreported analysis as though it had been performed or reported.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome of time to successful completion of pelvic ultrasound and a secondary outcome of pain measured by the Verbal Numerical Rating Scale. It records two outcome measures, but does not report a multiplicity procedure or describe how the outcomes were prioritized in any statistical testing plan. Because no comparative analyses are reported, there is no posted set of hypothesis tests from which to assess adjustment for multiple comparisons.
As a general statistical point, when several outcomes or tests are examined, the chance of at least one apparently notable result can increase unless the analysis plan accounts for multiplicity. Whether and how to address that issue depends on the planned inferential questions. The registry record does not report a statistical analysis plan, an interim-analysis plan, or a multiplicity adjustment. These details should not be inferred from the listing of primary and secondary outcomes.
The record does not report missing-data counts, reasons for missingness, imputation, or other handling of unavailable endpoint values. It also does not identify an intention-to-treat, per-protocol, or other analysis population. The reported group sizes are 22 and 23, but the record does not clarify how those groups relate to all randomized participants or whether every participant contributed an endpoint value. Consequently, it is not possible to determine from the registry alone whether missing observations affected the summaries or how robust the results are to different assumptions about missingness.
These omissions limit interpretation of the posted means and confidence intervals. They do not establish that data were missing or that a particular method was used; those matters are not reported in the registry record.
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 |
|---|---|---|---|
| Bladder Ultrasound | 0 | 22 | 0.0% |
| Standard of Care | 0 | 23 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Bladder Ultrasound | 0 of 22 |
| Standard of Care | 0 of 23 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Bladder Ultrasound | 0 of 22 |
| Standard of Care | 0 of 23 |
The registry reports serious adverse events for each group. In the Bladder Ultrasound group, 22 participants were at risk and zero were affected. In the Standard of Care group, 23 participants were at risk and zero were affected. The registry also reports zero deaths in each group. No serious adverse-event terms are listed.
These figures describe events recorded in the registry for the groups and at-risk counts stated. They are not a comparative safety analysis, and the record does not provide an uncertainty estimate for the event counts. Zero reported events does not prove that the risk is absent; it means that no serious adverse events were recorded in these posted results. The size of the study and the information available in the registry constrain how much can be inferred about uncommon events.
The record also includes other adverse events: zero affected among 22 at risk in the Bladder Ultrasound group and zero affected among 23 at risk in the Standard of Care group. The registry does not provide further event terms or additional safety-analysis details. These data should be read as event reporting, not as proof that the approaches have identical safety profiles or that no events occurred outside the reported categories or reporting period.
12. What the Result Does, and Does Not, Mean
The results establish that the registry reports mean times for each assigned group and gives a confidence interval around each mean. They offer a descriptive view of average time to completion among the participants represented in those summaries. The record reports 104.0 minutes for Bladder Ultrasound and 92.82 minutes for Standard of Care, with the corresponding 95% confidence intervals stated in the primary results.
Those summaries do not by themselves establish whether the approaches differ statistically or clinically. There is no posted estimate of the between-group difference, no interval for that contrast, and no reported hypothesis test. The record also does not report a threshold for a meaningful difference in time. It would therefore go beyond the evidence to declare one approach faster in a statistically established sense, or to claim equivalence or non-inferiority.
The results are also not a measure of diagnostic accuracy, patient satisfaction, or later health outcomes. The registry lists pain as a secondary outcome, but that result is not reported. The endpoint is a process measure: elapsed time from order placement to completion of pelvic ultrasound images, with success described in the brief summary as full visualization of the uterus and ovaries.
As a general statistical point, estimates from a trial are interpreted in light of their precision, analysis population, endpoint definition, and missing-data handling. The posted confidence intervals convey uncertainty about the group means, but do not resolve uncertainty about a treatment contrast that has not been reported. The record’s group sizes and summaries cannot reveal individual participant trajectories or variation within each group.
The appropriate reading is therefore limited but useful: the registry contains group-level estimates of average completion time and reports no serious adverse events in either group. It does not provide enough comparative analysis or methodological detail to support broader conclusions about the relative effects of the assigned approaches.
13. Why This Trial Matters Statistically
This trial raises a useful statistical question about how to evaluate a practical care process. The intervention and comparator are different strategies for preparing the bladder before pelvic imaging, and the primary endpoint measures elapsed time to completion. For this kind of question, it is important to distinguish a group’s average time from the comparative effect of assigning one approach rather than the other.
The registry illustrates why descriptive results and comparative inference are not interchangeable. A mean and its confidence interval describe each group separately. A direct comparison needs its own estimate and uncertainty. Without that contrast, readers cannot tell from the posted analysis whether the observed group summaries provide persuasive evidence of a difference, or how precisely any difference is estimated.
Randomization is a relevant design feature because it assigns participants to the approaches rather than simply comparing self-selected groups. Yet interpretation still depends on the analysis population, endpoint handling, and reporting of the planned comparison. Those details are not reported in the registry record. Their absence makes it harder to connect the design to a definitive estimate of the comparative effect.
The record also highlights a common issue in registry-based interpretation: an outcome may be listed without a posted result, and a completed status does not itself supply an analysis. Here, pain is named as a secondary outcome, but its result is not reported. The primary means are available, while a comparative analysis is not. Keeping those distinctions clear helps readers separate what the record documents from what it leaves unresolved.
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 limitations specific to this record affect interpretation. The registry reports group means and 95% confidence intervals for time to completion, but no estimate or test comparing the groups. It records zero analyses and indicates that values for a two-arm continuous-endpoint comparison are missing or not estimable. As a result, the posted primary results do not directly quantify the comparative effect.
The registry does not report the analysis population, participant-level endpoint data, the number or reasons for incomplete observations, or how such observations were handled. The endpoint timeframe is stated as baseline to 180 minutes, but the record does not explain how the analysis treated participants whose images were not completed within that timeframe. The registry also does not describe the method used to calculate the confidence intervals.
Further design and analysis details are not reported in the registry record, including eligibility criteria, allocation concealment, the protocol’s sample-size justification, a statistical analysis plan, interim analyses, and a multiplicity procedure. The registry lists a secondary pain outcome but does not post its result. These gaps limit assessment of the planned analysis and the completeness of outcome reporting; they do not establish that any particular method or event occurred.
The enrollment is 45, and the posted group sizes are 22 and 23. The record does not explain whether the posted analyses include all enrolled or randomized participants. The results therefore should be interpreted as the summaries recorded, without assuming details about adherence, missingness, or participant flow that are not reported.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: BULLET: Bladder Ultrasound Limits Length (of Time), Expedites Treatment — NCT03860311.
- Registry record last updated 2022-06-01; status last verified 2022-05.
- Results first posted 2022-06-01.
- 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
BULLET (NCT03860311) is a completed randomized, parallel-group study with no masking. It enrolled 45 participants and compared point-of-care bladder ultrasound with urethral catheterization for bladder filling before pelvic ultrasound in pediatric emergency patients with abdominal or pelvic complaints. The primary endpoint was time from order placement to completion of pelvic ultrasound images, with full visualization of the uterus and ovaries described as successful completion.
The registry reports a mean of 104.0 minutes (95% confidence interval 82.64 to 125.3) for Bladder Ultrasound and 92.82 minutes (95% confidence interval 80.29 to 105.3) for Standard of Care. It does not report a comparative analysis. Pain measured by the Verbal Numerical Rating Scale is listed as a secondary outcome, but its result is not reported. Zero serious adverse events and zero deaths are recorded in each group.