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 Study Dynamic Haptic Robotic Trainer (DHRT) and DHRT+ for Central Venous Catheterization Insertion Training for Residents (NCT04541446), a randomized na study. The primary outcome is Number of Internal Jugular Central Venous Catheters With and Without Mechanical Complication.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04541446 |
| Phase | NA |
| Condition | Central Line Complication, Central Line Infection |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 773 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Milton S. Hershey Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
First-year medical residents at Milton S. Hershey Medical Center and Cedars-Sinai Medical Center were to receive training in central venous catheterization. The primary-outcome description says complication data came from retrospective chart review at Milton S. Hershey Medical Center only. It also says the 2020 surgical-resident cohort was not included in participants analyzed because the chart review covered insertions in the specified tracked years.
Intervention
One training approach used the Dynamic Haptic Robotic Trainer (DHRT), which trains the needle-insertion component of central venous catheterization. The other used the Advanced Dynamic Haptic Robotic Trainer (DHRT+), described as offering whole-procedure training.
Comparator
The registry describes a randomized, parallel comparison of residents assigned to DHRT training or DHRT+ training. Masking is listed as none. The brief summary says the training technique did not differ from what was already taught at the participating institutions, and residents had to pass their institution's existing skills assessment.
Primary question
The primary outcome concerns the number of internal jugular central venous catheters with and without a mechanical complication. The complication composite includes hematoma, arterial puncture, pneumothorax, hemothorax, catheter misplacement, and vessel stenosis. The registry record does not report numerical results comparing the training groups on this outcome, so the direction and precision of any difference cannot be assessed from the record.
3. Trial Design
The registry describes a randomized, parallel-group study with no masking. The listed interventions are DHRT and DHRT+. DHRT trains residents in the needle-insertion component of central venous catheterization; DHRT+ is described as providing whole-procedure training. The record lists enrollment of 773 and identifies Milton S. Hershey Medical Center as sponsor. It lists the phase as NA.
The brief summary describes entering first-year residents at Milton S. Hershey Medical Center and Cedars-Sinai Medical Center being taught to perform central venous catheterization with one of the two devices. Residents were to be assessed by the devices during training and required to pass the same skills assessment already required at their institution. After passing, they were to perform procedures under supervision. The record says the training technique did not differ from what was then taught at either institution.
The primary-outcome follow-up is organized by training period and tracked insertion year: residents trained in 2021 correspond to the DHRT period and tracked insertions in 2022; residents trained in 2022–2024 correspond to the DHRT+ period and tracked insertions in 2023–2025. The record says DHRT deployment began June 2021 and DHRT+ began June 2022. This calendar structure matters when interpreting the comparison: training group and insertion period are linked in the outcome description, so the record does not establish that any group contrast isolates the training device from all changes over time.
The primary-outcome description is based on retrospective chart review at Milton S. Hershey Medical Center only, despite the training population including residents at two institutions. The record marks the study completed and lists a primary completion date of 2025-12-31. It says data collection is complete. It does not report the randomization procedure, concealment method, or whether outcome assessors were blinded.
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 | Residents to Receive Dynamic Haptic Robotic Training | Residents to Receive Advanced Dynamic Haptic Robotic Training |
|---|---|---|
| STARTED | 199 | 574 |
| COMPLETED | 199 | 574 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Outcome data reflect retrospective chart review at Milton S. Hershey Medical Center only. The 18 residents in the 2020 surgical-resident cohort are not included in Participants Analyzed because chart review covered only insertions in the tracked years listed in the Time Frame (2022 for DHRT; 2023-2025 for DHRT+). Their insertions (2021) were not reviewed, so no outcome data were collected for these participants.
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.
Population: Enrollment reflects first-year residents at Milton S. Hershey Medical Center and Cedars-Sinai Medical Center who consented to participate in the study and were trained under the DHRT or DHRT+ program.
| Characteristic | Unit | Residents to Receive Dynamic Haptic Robotic Training | Residents to Receive Advanced Dynamic Haptic Robotic Training | Total |
|---|---|---|---|---|
| Participants analysed | 199 | 574 | 773 | |
| Age, Customized: 18-65 | Participants | 199 | 574 | 773 |
| Sex/Gender, Customized: Participants – Male | Participants | 80 | 263 | 343 |
| Sex/Gender, Customized: Participants – Female | Participants | 118 | 309 | 427 |
| Sex/Gender, Customized: Participants – Unknown | Participants | 1 | 2 | 3 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 1 | 1 |
| Race (NIH/OMB): Asian | Participants | 56 | 184 | 240 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 2 | 20 | 22 |
| Race (NIH/OMB): White | Participants | 110 | 282 | 392 |
| Race (NIH/OMB): More than one race | Participants | 8 | 37 | 45 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 23 | 50 | 73 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 13 | 48 | 61 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 186 | 524 | 710 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 2 | 2 |
| Region of Enrollment: United States | participants | 199 | 574 | 773 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Internal Jugular Central Venous Catheters With and Without Mechanical Complication, measured over Residents trained in 2021 (tracked insertion year 2022) for the DHRT period; residents trained in 2022-2024 (tracked insertion years 2023-2025) for the DHRT+ period..
| Element | Registry entry |
|---|---|
| Result type | Count Of Units |
| Measure of spread | not applicable |
| Unit | Internal Jugular Central Venous Catheter |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the number of internal jugular central venous catheters with and without mechanical complications. It is a count outcome, not a time-to-event measure or a continuous score. Mechanical complications are defined as a composite of hematoma, arterial puncture, pneumothorax, hemothorax, catheter misplacement, and vessel stenosis. The record says these events were identified using International Classification of Diseases diagnosis codes flagged as not present at hospital admission.
A composite endpoint can capture several kinds of procedure-related harm in one outcome. This can be useful when individual event types are uncommon, but the combined count does not show which component contributes most. It also treats each listed complication as part of the same endpoint, even though the components may differ in clinical seriousness and frequency. The registry record does not give component-specific counts or explain how multiple complications in one catheterization were handled.
Counts are interpretable only alongside a defined denominator, such as the number of eligible catheterizations or the number of residents contributing procedures. The record gives the tracked years and the chart-review site, but numerical primary-outcome counts and an analysis denominator are not reported in the registry record. Without those values, the event frequency, group contrast, and uncertainty cannot be evaluated. The endpoint is used to assess whether complication counts differed across training periods; the registry record does not report the result of that comparison.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the primary outcome and its observation periods, but does not report numerical results for that outcome. It therefore does not establish how many catheters were recorded with complications, how many were recorded without complications, or whether the DHRT and DHRT+ periods differed. No effect estimate, confidence interval, or p-value for the primary outcome is reported in the registry record. The direction, magnitude, and precision of a primary-outcome contrast cannot be determined from the record.
The endpoint is a count of catheters, and the description links different resident-training years to different insertion years. DHRT is associated with insertions tracked in 2022, while DHRT+ is associated with insertions tracked in 2023–2025. This makes the calendar period part of the interpretation. In general, outcomes observed in different periods may also reflect changes in clinical practice, patient mix, documentation, or other aspects of care. The registry record does not report analyses addressing such factors, so their influence cannot be assessed.
The overall enrollment is 773, but that figure should not be treated as the denominator for the primary complication endpoint. The primary outcome is based on retrospective review at Milton S. Hershey Medical Center, and the record notes that the 2020 surgical-resident cohort is not included in participants analyzed because the review covered the tracked insertion years. It does not report the number of catheters reviewed or the number of residents contributing to the endpoint analysis. Enrollment and outcome-analysis populations need not be the same.
The adverse-event record lists 199 people at risk in the DHRT group and 574 in the DHRT+ group, with zero serious and zero other adverse events affected in each group. These are adverse-event figures, not primary mechanical-complication results. They do not supply the missing catheter counts or an estimate for the primary outcome, and they should not be read as evidence that no mechanical complications occurred.
Statistical interpretation depends on the estimate and its uncertainty, not only on whether a test crosses a significance threshold. A confidence interval, when reported, describes a range of effect sizes compatible with the data and model; it also conveys how precisely the contrast is estimated. Here, no primary-outcome estimate or confidence interval is reported in the registry record. The available registry information supports a description of the question and data collection, but not a conclusion about the comparative primary outcome.
9. Statistical Methods Explained
What kind of outcome is being measured?
The primary endpoint is a count: the number of internal jugular central venous catheters classified with or without a mechanical complication. Count outcomes differ from continuous outcomes such as a score, and from binary outcomes recorded once for each participant. The unit named in the registry is an internal jugular central venous catheter. A meaningful group comparison therefore depends on knowing how many catheters were observed in each group or period, as well as the complication counts.
When follow-up exposure differs, analysts may compare rates rather than raw counts. A rate needs an appropriate exposure denominator, such as the number of procedures observed. The registry record does not report primary-outcome counts, denominator totals, or a rate analysis. It is therefore not possible to interpret the outcome as a rate or calculate a group contrast from the registry information.
Why can counts show more variation than a simple model expects?
As a general statistical point, basic count models often assume that the variance is tied to the mean. Real-world counts can vary more than that assumption allows. This is called over-dispersion. If it is present and ignored, standard errors can be too small and confidence intervals too narrow. More flexible count models can account for extra variation, but the choice depends on the design and the observed data. The registry record does not report a statistical model or a check for over-dispersion.
Another general issue is clustering. Several catheterizations may be associated with the same resident, clinical team, or period. Outcomes within a cluster can be more alike than outcomes from unrelated observations. Treating every catheter as fully independent in that situation can understate uncertainty. The registry record does not describe the number of procedures per resident or whether the analysis accounted for clustering. This is not evidence that clustering was ignored; the analysis is not reported in the registry record.
What does randomization contribute?
In general, random assignment can make groups more comparable at the start of a study, on average, and can reduce confounding in a comparison of assigned interventions. The registry lists the study as randomized, but does not describe how randomization was generated, whether assignment was concealed, or what unit was randomized. Those details matter for assessing how well the design protects against selection bias.
The outcome description also links training groups to different calendar periods: the DHRT period is associated with tracked insertions in 2022, while the DHRT+ period is associated with insertions in 2023–2025. A randomized label alone does not explain how calendar time was handled in the outcome analysis. The registry record does not report an adjusted model or other methods for separating training-group differences from period differences.
How should uncertainty be read?
In general, a confidence interval expresses uncertainty around an estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but neither interval alone establishes whether an effect is important. A p-value measures how unusual the data would be under a specified null model; it does not give the probability that a treatment effect is true. For a count outcome, interpretation also depends on the effect measure used, the model, and the unit of analysis.
No primary-outcome estimate, confidence interval, or p-value is reported in the registry record. There is consequently no inferential result to interpret. A statement that data collection is complete does not, by itself, provide a statistical result or establish the precision of the comparison.
What can planning calculations show?
In general, sample-size planning calculations describe the number of observations needed under stated assumptions to detect a specified effect with a chosen error rate and power. Such calculations are planning illustrations, not observed power after a study is completed. The registry record says that a planning illustration is based on a fraction of the observed effect and specifies a two-sided significance level of 0.05, equal allocation, and a normal approximation. It does not report the primary outcome as one comparison because it has several categories or time points. The specific planning results are not reported in the registry record.
Planning assumptions should not be confused with the trial's own design justification. The registry record does not report a sample-size justification for the trial. Nor does it report interim analyses, stopping rules, or a prespecified statistical analysis plan. These omissions prevent assessment of how the completed enrollment relates to the intended precision or planned hypothesis tests. They do not establish that no such plans existed outside the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures, but the primary outcome itself includes several categories or time points and is not reduced to one comparison in the posted statistical summary. The number of analyses is listed as zero. As a result, the registry record does not provide a set of inferential tests from which to assess multiplicity or identify which comparisons were statistically prioritized in the results.
Multiplicity arises when many outcomes, time points, groups, or subgroup comparisons are tested. In general, the more tests considered, the greater the chance of at least one apparently unusual result arising by chance. Prespecified primary outcomes and suitable adjustment methods can help make interpretation more reliable. The record does not report a multiplicity adjustment, a testing hierarchy, or how multiple categories and time points were handled.
Missing-data methods and analysis populations are also not described in enough detail to assess them. The outcome description states that retrospective chart review was limited to Milton S. Hershey Medical Center and excludes the 2020 surgical-resident cohort from participants analyzed because the chart review covered the specified tracked years. It does not report the number of eligible records, incomplete records, excluded catheterizations, or the reasons for any exclusions beyond that cohort-level explanation.
The registry record does not report whether all randomized residents were included in an intention-to-treat analysis, whether any per-protocol or other analysis population was used, or how missing outcome information was handled. The 773 enrollment figure should not be assumed to equal the number of residents or catheterizations in the primary analysis. Without those details and the numerical outcome results, the potential effects of missingness, exclusions, and multiple comparisons cannot be quantified.
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 |
|---|---|---|---|
| Residents to Receive Dynamic Haptic Robotic Training | 0 | 199 | 0.0% |
| Residents to Receive Advanced Dynamic Haptic Robotic Training | 0 | 574 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Residents to Receive Dynamic Haptic Robotic Training | 0 of 199 |
| Residents to Receive Advanced Dynamic Haptic Robotic Training | 0 of 574 |
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 |
|---|---|
| Residents to Receive Dynamic Haptic Robotic Training | 0 of 199 |
| Residents to Receive Advanced Dynamic Haptic Robotic Training | 0 of 574 |
The registry's adverse-event entries list 199 people at risk in the DHRT group and 574 in the DHRT+ group. For each group, the record lists zero affected by serious adverse events and zero affected by other adverse events, with zero deaths. These entries describe the adverse-event reporting fields; they are separate from the primary endpoint of catheter-level mechanical complications.
Zero reported affected participants means that the record does not list an affected participant for these adverse-event categories. It does not establish that every possible harm was actively sought, that event ascertainment was complete, or that no event could occur outside the recorded categories. The record does not describe the adverse-event collection methods, definitions, or observation window. Those details are not reported in the registry record.
The group counts at risk should not be treated as the primary-outcome denominators. The primary endpoint concerns catheters and is based on retrospective chart review at Milton S. Hershey Medical Center. The adverse-event figures do not report how many catheters were reviewed or how many had mechanical complications. They therefore cannot be used to infer the primary outcome or its uncertainty.
12. What the Result Does, and Does Not, Mean
The study addresses a practical training question: whether resident training with a device focused on needle insertion or a device offering whole-procedure training is associated with different central-line complication counts. The registry describes randomized allocation and a retrospective review of mechanical complications identified from diagnosis codes at Milton S. Hershey Medical Center. It also identifies the relevant training and insertion periods.
What the registry record does not provide is the numerical primary-outcome result. There are no reported complication counts, group estimates, confidence intervals, or p-values for the primary comparison. Consequently, the record cannot establish the direction, size, or precision of any difference between the training periods. The adverse-event entries are not a substitute for these missing primary results.
Even with numerical results, interpretation would depend on the analysis population, the number of catheters observed, how repeated procedures and clustering were handled, and whether calendar-period differences were addressed. The outcome review came from one of the two training institutions, and the DHRT and DHRT+ outcomes correspond to different tracked insertion years. These design features limit what a simple group contrast could establish unless the analysis accounts for them appropriately. The registry record does not report whether it did so.
The record marks the study completed and says data collection is complete. Completion is a status, not an estimate of comparative performance. The available information supports describing the study design, endpoint definition, and data source. It does not support a claim that either training approach led to more or fewer complications, nor a claim about the clinical importance of any difference. The statistical result is not reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically interesting because the intervention is a resident-training approach while the primary outcome is a count of clinical procedures with or without complications. That creates a link between training assignment, residents, individual catheterizations, and the calendar period in which procedures were performed. The relevant unit for outcome measurement is the catheter, but the assignment unit and the dependence among procedures are not described in the registry record.
Those levels matter. In general, if outcomes from procedures performed by the same resident are correlated, the amount of independent information is less than the raw number of procedures suggests. Likewise, if one training approach is observed in one period and another in later years, changes over time may be intertwined with group differences. Clear reporting of denominators, analytic units, and methods for dependence and time would help readers assess the precision and interpretation of the comparison.
The composite endpoint also raises a useful measurement question. Combining several complications can provide a broad outcome, while obscuring which events drive the total. Component counts and definitions can help show whether a result is consistent across event types and whether coding-based identification captures the intended events. The record specifies the components and says diagnosis codes flagged as not present at admission were used, but does not report component-specific results.
Finally, the registry record illustrates the difference between a completed study and a reported statistical result. It includes design and outcome-definition details, but no numerical primary-outcome analysis. Without estimates and uncertainty, readers cannot assess whether the observed data are compatible with a wide range of effects or with a more precise comparison. Transparent reporting of the analysis population, event counts, model, and uncertainty is essential for evaluating such a study.
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 most direct limitation of the registry information is that numerical primary-outcome results are not reported. The endpoint definition is available, but there are no complication counts, comparison estimates, confidence intervals, or p-values. This prevents assessment of effect direction, magnitude, and precision.
The outcome data are described as retrospective chart review at Milton S. Hershey Medical Center only, while residents were trained at Milton S. Hershey Medical Center and Cedars-Sinai Medical Center. The record does not report outcome review at the second institution. The 2020 surgical-resident cohort is explicitly not included in participants analyzed because the review covered only the tracked insertion years. The number of residents and catheterizations contributing to the primary analysis is not reported in the registry record.
The outcome periods differ by training approach: DHRT is linked to tracked insertions in 2022, and DHRT+ to insertions in 2023–2025. This means calendar time is relevant to interpretation. The registry record does not report whether time-related changes or differences between institutions were accounted for. It also does not report the randomization unit, allocation concealment, outcome-assessor masking, or handling of repeated procedures.
The primary endpoint combines several types of mechanical complication identified using diagnosis codes. Component-specific counts and coding validation are not reported in the registry record. Nor are missing-record totals, analysis populations, or methods for missing outcomes described. These reporting gaps limit appraisal of outcome completeness and model suitability; they do not establish that the underlying study lacked procedures for addressing these issues.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study Dynamic Haptic Robotic Trainer (DHRT) and DHRT+ for Central Venous Catheterization Insertion Training for Residents — NCT04541446.
- Registry record last updated 2026-11-04; status last verified 2026-10.
- Results first posted 2026-11-04.
- 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 record describes NCT04541446, a randomized, parallel study comparing DHRT with DHRT+ for central venous catheterization training among first-year residents. Masking is listed as none, enrollment as 773, and the phase as NA. The sponsor is Milton S. Hershey Medical Center. The record marks the study completed and lists a primary completion date of 2025-12-31.
The primary outcome is the number of internal jugular central venous catheters with and without a composite mechanical complication. Outcome data are described as retrospective chart review at Milton S. Hershey Medical Center, with tracked insertion years of 2022 for the DHRT period and 2023–2025 for the DHRT+ period. The record says data collection is complete.
Numerical primary-outcome results, inferential analyses, analysis populations, and missing-data methods are not reported in the registry record. The adverse-event entries list zero affected participants in both groups, but those figures do not describe the primary catheter-level outcome.