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 Determination of the Prevalence and Severity of Expiratory Flow Limitation in Chronic Obstructive Pulmonary Disease Patients (NCT03851510), a non-randomized phase not stated study. The primary outcome is Overall Prevalence of Expiratory Flow Limitation.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03851510 |
| Phase | Phase not stated |
| Condition | Chronic Obstructive Pulmonary Disease, Noninvasive Ventilation |
| Allocation | Non-Randomized |
| Design model | Sequential |
| Masking | None (open label) |
| Enrollment | 57 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Philips Respironics |
| Results posted | Yes |
2. Clinical Question
Population
People with a diagnosis of chronic obstructive pulmonary disease (COPD) were the target population. The brief summary describes a community COPD population and an intended age range of 40 to 80 years. The registry lists enrollment of 57, while the brief summary describes a plan to include 100 people; the reason for this difference is not reported in the registry record. The primary endpoint description also notes one participant screened fail and data not collected for the two discontinued participants.
Intervention
The study used two devices for screening: participants were first screened for expiratory flow limitation (EFL) with the Resmon Pro and screened again with the Vector ventilator. The Vector protocol described a 20 minute titration for participants with EFL. The brief summary says the device would assess pressure therapy needed to eliminate EFL, with the final expiratory positive airway pressure recorded.
Comparator
There was no randomized control group. The device sequence is a within-study screening procedure, not a randomized, like-for-like treatment comparison. A secondary outcome concerns the percentage of participants with EFL according to Resmon Pro whose EFL is abolished during Vector screening, but its result is not reported in the registry record.
Primary question
The primary question is how prevalent EFL was in the screened COPD population under the registry’s definition: a supine Vector DeltaXRS value greater than or equal to 2.8, counting both EFL and indeterminate EFL. The endpoint timeframe is 1 day. The numerical prevalence result, the number meeting the definition, and an uncertainty interval are not reported in the registry record.
3. Trial Design
This was a non-randomized, unmasked study classified in the registry as sequential. Its stated purpose was epidemiologic: to assess the prevalence and severity of expiratory flow limitation in a community COPD population and explore how EFL may relate to physiological biomarkers. The registry lists chronic obstructive pulmonary disease and noninvasive ventilation as conditions. Philips Respironics is the listed sponsor. The study is marked terminated; the reason for termination is not reported in the registry record.
The registry lists enrollment as 57. The brief summary describes an intended enrollment of 100 male and female participants with COPD between the ages of 40 and 80. These statements describe different enrollment figures, and the reason for the difference is not reported in the registry record. The listed study start is 2019-03-14, and primary completion is listed as 2023-11-15.
Participants were to be screened first with the Resmon Pro and then with the Vector device. The Vector description says participants with EFL would undergo a 20 minute titration protocol. The brief summary describes a one-visit study: if EFL was not detected during screening after 5 minutes, the participant would not continue; if detected, the Vector device would continue measuring the therapy level needed to eliminate EFL. The description also says 20 minutes of pressure therapy would be provided and the final EPAP determined to abolish EFL recorded. Whether these procedures were completed as planned is not reported in the registry record.
Because allocation was non-randomized and the device sequence does not define randomized treatment groups, differences between device assessments should not be interpreted as effects from a controlled treatment comparison. The registry’s non-randomized design also limits causal conclusions about therapy. The operational details behind the sequential model classification are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | All Participants That Were Consented. |
|---|---|
| STARTED | 57 |
| COMPLETED | 54 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | All Participants That Were Consented. |
|---|---|
| Screen Fail | 1 |
| Adverse Event | 1 |
| Withdrawal by Subject | 1 |
Analysis population for the primary outcome, as defined in the registry: One participant screened fail and data was not collected for the two discontinued 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: Includes only participants that were eligible. Baseline data was not available for the screened fail subject.
| Characteristic | Unit | All Participants That Were Consented. |
|---|---|---|
| Participants analysed | 56 | |
| Age, Continuous | years | 61 (SD 8.1) |
| Sex: Female, Male: Female | Participants | 32 |
| Sex: Female, Male: Male | Participants | 24 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 55 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 14 |
| Race (NIH/OMB): White | Participants | 41 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 56 |
6. Primary Endpoint
The registry lists the primary outcome as Overall Prevalence of Expiratory Flow Limitation, measured over 1 day.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is titled overall prevalence of expiratory flow limitation. It is defined using the Vector EFL device: participants are counted as meeting the definition when their supine DeltaXRS value is greater than or equal to 2.8. The registry explicitly includes both indeterminate EFL and EFL in the overall prevalence definition. The endpoint timeframe is 1 day.
Prevalence is used to describe how common a defined condition or finding is in a specified population. In this study, the threshold gives the endpoint an operational definition: the count or percentage depends on how many screened participants fall into the included categories under that device and measurement condition. It does not, by itself, establish why EFL is present or whether a device-based classification corresponds to a clinical outcome.
The registry lists the endpoint unit as participants and its parameter as a count of participants, while the endpoint description says prevalence will be expressed as a percentage. No count meeting the definition or percentage estimate is reported in the registry record. An uncertainty interval and details of how indeterminate readings were recorded beyond their inclusion in the endpoint are also not reported in the registry record. Consequently, the registry description establishes what was intended to be measured but does not give a numerical estimate of prevalence or its precision.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a study intended to estimate the prevalence and severity of EFL in people with COPD. It defines the primary endpoint using a supine Vector DeltaXRS threshold of greater than or equal to 2.8 and includes indeterminate EFL as well as EFL in the prevalence definition. However, the numerical primary endpoint result is not reported in the registry record. The record therefore does not establish how many participants met the definition, what percentage this represents, or how precise that estimate is.
Precision matters when interpreting a prevalence estimate. In general, an estimate is more informative when accompanied by an interval describing the uncertainty associated with the observed data. A confidence interval is a range produced by a statistical procedure that communicates uncertainty around an estimate under its assumptions. The interval for this endpoint is not reported in the registry record. Without the estimate and its interval, the result cannot be assessed for either magnitude or precision.
The registry lists enrollment of 57, while its brief summary describes an intended enrollment of 100. The reason for the difference is not reported in the registry record. The primary endpoint description also notes one participant screened fail and data not collected for the two discontinued participants. Those notes are relevant to understanding the available endpoint data, but the record does not provide a complete accounting of the analysis population or explain how missing observations were handled.
The study is non-randomized and unmasked. Its two devices are described as successive screening procedures rather than randomized comparator arms. A device-to-device difference, if reported, would therefore require careful interpretation: the registry does not describe a randomized design that separates device effects from order, measurement, or participant-level influences. The outcome concerning participants whose EFL is identified by Resmon Pro and abolished during Vector screening is a secondary outcome, but its result is not reported in the registry record.
The brief summary describes a Vector titration procedure and recording of final EPAP, and the secondary outcomes include correlations of final EPAP with FEV1 and screening DeltaXrs. The registry record does not report those numerical results, correlation estimates, or their uncertainty. It therefore supports description of the research questions and procedures, not conclusions about the size or direction of relationships or the effect of pressure therapy.
The registry’s status is terminated, but the reason is not reported. Termination alone does not explain whether planned measurements were completed, why enrollment differed from the intended number, or whether any findings were considered. Those details are not reported in the registry record. The posted information should therefore be read as a limited account of design and selected safety counts, not as a complete statistical report of the primary or secondary outcomes.
9. Statistical Methods Explained
What does a prevalence endpoint estimate?
In general, prevalence describes the proportion of a defined population that meets a specified condition or measurement rule. The rule is important because it determines who is counted. In this study, the primary definition uses a supine Vector DeltaXRS value greater than or equal to 2.8, and it includes both EFL and indeterminate EFL. That makes the endpoint a device- and definition-specific prevalence measure; it should not be treated as a general measure of every possible definition of EFL.
A count and a percentage answer related but different questions. The count records how many participants meet the criterion, while the percentage places that count in relation to a defined analysis population. The registry lists the endpoint unit as participants and the parameter as a count, while the description says overall prevalence will be a percentage. The actual count, percentage, and analysis denominator are not reported in the registry record, so the estimate cannot be reconstructed from the listed enrollment alone.
Why does the analysis population matter?
A prevalence estimate depends on which participants are included and whether their endpoint measurements are available. In general, excluding participants with missing or indeterminate measurements can change the estimate, especially if the missingness is related to the outcome. This study explicitly includes indeterminate EFL in its primary definition, but it does not report how the indeterminate category was counted in the numerical analysis. The endpoint description notes one participant screened fail and data not collected for the two discontinued participants. Other details about exclusions, missing measurements, or the exact analysis population are not reported in the registry record.
When a study reports a percentage, the denominator should correspond to the population used for that calculation. A clear report would identify the number meeting the endpoint and the number with eligible data, along with how unavailable or indeterminate data were handled. Those numerical details are not reported in the registry record. The enrollment entry should not automatically be treated as the denominator for the primary endpoint.
How should uncertainty be understood?
In general, an interval estimate communicates uncertainty around a sample estimate. A confidence interval is constructed using a statistical method and assumptions; it is not a guarantee that the true population value lies within the particular interval. For a binary endpoint such as meeting or not meeting a threshold, the method should be appropriate to the data and the analysis population. The registry record does not report a primary prevalence estimate, an interval, or the method used to calculate uncertainty. It is therefore not possible to evaluate the numerical precision of the planned estimate.
The registry describes the endpoint as a count of participants and a percentage, but does not state a statistical analysis plan for the primary endpoint. The exact estimation method, any adjustment, and any approach to sensitivity analyses are not reported in the registry record. General descriptions of prevalence estimation do not establish which method was actually used in this study.
What does the non-randomized sequence imply?
In general, random allocation can help balance measured and unmeasured participant characteristics across treatment groups. This study is classified as non-randomized and unmasked, and its device descriptions indicate that participants were screened with Resmon Pro and then screened with Vector. That sequence can support descriptive comparison of measurements, but it is not equivalent to random assignment to independent device groups. The registry record does not report a randomized comparator or a method that would isolate device effects from order or measurement effects.
The registry classifies the study model as sequential, but the details of that classification are not reported. It should not be taken as evidence of sequential stopping, interim monitoring, or a particular analysis strategy. Whether interim analyses were planned or conducted is not reported in the registry record.
What are planning illustrations?
In general, sample-size planning uses assumptions about a target effect, variability, allocation, and a statistical decision rule to illustrate how much information a future study may need. The planning assumptions described for this study use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. The registry notes that this is a planning illustration based on the observed effect, not the trial’s own design. Numerical planning estimates are not reported in the registry record.
Such planning figures are not observed outcomes and do not indicate the probability that the completed study detected a real effect. They are not observed power. In this case, the non-randomized registry description does not establish two like-for-like arms for causal comparison, and the planning assumptions should not be mistaken for the study’s actual allocation or analysis plan. The registry does not report a sample-size justification for the trial itself.
What analysis information is absent?
The registry lists four outcome measures and one analysis, but does not report the primary estimate or the methods used to produce it. Details such as the estimator, uncertainty calculation, missing-data procedure, covariate adjustment, and any prespecified subgroup analysis are not reported in the registry record. The same limitation applies to the secondary correlations involving final EPAP, FEV1, and screening DeltaXrs: their estimates and statistical methods are not reported. These absences prevent assessment of whether the reported analysis, if any, followed a prespecified plan or how robust it would be to alternative choices.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists four outcome measures and one analysis. It does not report whether the outcomes were organized into a prespecified hierarchy, whether any adjustment for multiple comparisons was planned, or how the primary endpoint was distinguished statistically from secondary outcomes. The multiplicity plan is not reported in the registry record. Without that information, the risk of obtaining apparently notable findings through repeated testing cannot be evaluated. This is particularly relevant to the listed secondary outcomes, which include correlations of titrated final EPAP with FEV1 and screening DeltaXrs, as well as the percentage of Resmon Pro-positive participants whose EFL is abolished during Vector screening.
Missing-data information is limited. The primary endpoint description notes one participant screened fail and data not collected for the two discontinued participants. It does not describe a full analysis population, give endpoint-specific denominators, or state whether any measurements were otherwise missing. The method used to handle missing observations, and whether any sensitivity analysis was performed, are not reported in the registry record.
The endpoint definition includes indeterminate EFL alongside EFL, but the numerical handling and count of indeterminate observations are not reported. The registry also does not report whether any participants were excluded after screening or how such exclusions would affect the denominator. Because prevalence depends on the population included in the numerator and denominator, these omissions limit interpretation of both the endpoint and its precision. The study’s analysis populations and the approach to missing data 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 |
|---|---|---|---|
| All Participants That Were Consented. | 0 | 57 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| All Participants That Were Consented. | 0 of 57 |
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 |
|---|---|
| All Participants That Were Consented. | 1 of 57 |
Most frequent non-serious adverse event terms
| Event term | Organ system | All Participants That Were Consented. |
|---|---|---|
| Coughing | Respiratory, thoracic and mediastinal disorders | 1 of 57 |
The safety entry is titled All Participants That Were Consented. It lists 57 participants at risk for serious adverse events and 0 affected. For the separate other adverse-event category, it lists 57 at risk and 1 affected. Deaths are listed as 0. These are counts recorded in the registry; the entry does not give event descriptions or a breakdown by device or study procedure. No serious adverse-event terms are listed.
In general, an affected-participant count indicates how many participants were recorded as having at least one event in the category; it is not necessarily a count of individual events. The registry does not explain the event-counting convention in this entry, so the counts should be read as affected participants rather than a complete event tally. The single participant in the other category should not be assigned a cause based on these figures. The registry record does not report whether the event was judged related to a device, procedure, or study participation.
These figures are descriptive safety counts. They do not establish that a risk is absent, and they do not support a comparison between treatments because the study was non-randomized and does not present like-for-like control groups. The timing and follow-up period for adverse-event collection are not reported in the registry record. The safety figures also do not substitute for the missing primary prevalence result or for detailed clinical outcome reporting.
12. What the Result Does, and Does Not, Mean
The study addresses an epidemiologic question: how often EFL, defined by a specified Vector measurement threshold while supine, was identified in a COPD population. That is a descriptive question about a defined sample and measurement procedure. It is distinct from determining whether a therapy improves health outcomes, whether one device is superior to another, or whether a screening result predicts future clinical events.
The registry record gives the endpoint definition and the intended sequence of device assessments, but it does not report the primary prevalence estimate. It also does not report the count meeting the threshold, an uncertainty interval, or numerical results for the listed secondary outcomes. As a result, the posted information cannot establish the observed prevalence, the precision of an estimate, or the strength of any relationship between final EPAP and FEV1 or screening DeltaXrs.
The procedure description says that participants with EFL detected by the Vector device would undergo titration and that final EPAP would be recorded. This description explains what was intended to be measured; it is not evidence that the procedure changed a clinical outcome. The secondary outcome about EFL being abolished during Vector screening is likewise a planned assessment, and its numerical result is not reported in the registry record.
Non-randomized, unmasked screening can describe findings in the participants assessed, but it does not provide the same basis for causal attribution as a randomized controlled comparison. The two-device sequence is not a randomized treatment contrast. Any measured differences across screening steps would need to be interpreted in light of device order and measurement conditions, details that are not statistically analyzed in the registry information.
The appropriate conclusion is therefore limited: the registry documents a study designed to assess EFL prevalence and related measures, with a defined threshold and a stated screening sequence. It does not provide the numerical outcome evidence needed to quantify prevalence or judge its precision. No conclusion about treatment benefit, harm, or comparative effectiveness follows from the design description or the listed safety counts alone.
13. Why This Trial Matters Statistically
This study raises practical statistical issues that recur in device-based epidemiology. A prevalence estimate is only interpretable when the case definition, measurement conditions, numerator, and denominator are clear. Here, the registry specifies a supine Vector DeltaXRS threshold of greater than or equal to 2.8 and includes indeterminate EFL in the endpoint. That explicit definition is useful, but the numerical count, percentage, and uncertainty interval are not reported in the registry record.
The registry also illustrates why enrollment and analysis populations should not be treated as interchangeable. Enrollment is listed as 57, while the brief summary describes an intended enrollment of 100. The endpoint description separately notes one participant screened fail and data not collected for the two discontinued participants. Without a complete accounting of who contributed endpoint data, readers cannot identify the denominator or determine how incomplete observations affected the estimate.
The device sequence matters statistically as well. Resmon Pro screening followed by Vector screening can generate paired or sequential measurements, but the design is non-randomized and unmasked. It does not create randomized device groups. Careful analysis and reporting would need to distinguish descriptive agreement or change across screening steps from evidence that one device or a treatment caused a difference. The registry does not report the analysis details or numerical results for these comparisons.
Finally, the study’s stated prevalence objective differs from a treatment-effect objective. A prevalence study can characterize how often a defined finding occurs in the studied population, while correlations with EPAP, FEV1, or DeltaXrs address associations. Neither type of result alone establishes clinical benefit. Because the primary and secondary numerical results are not reported in the registry record, the record is most useful for clarifying the design and intended questions, rather than supporting conclusions about the magnitude or precision of findings.
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 important limitation for interpreting the registry record is that the primary prevalence estimate and its uncertainty are not reported. The outcome definition is available, but the number meeting it, the percentage, and an interval estimate are absent. This prevents assessment of the endpoint’s magnitude and precision.
Enrollment information is not fully reconciled: the registry lists 57, while the brief summary describes an intended enrollment of 100. The reason for the difference is not reported in the registry record. The endpoint description notes one participant screened fail and data not collected for the two discontinued participants, but it does not give a complete endpoint-specific analysis population or explain how unavailable measurements were handled.
The study is non-randomized and unmasked, and the device sequence is not a like-for-like randomized comparison. This limits causal interpretation of any difference between screening steps. The registry does not report methods addressing order effects, measurement agreement, or other sources of systematic difference. The operational details behind the sequential model classification are also not reported.
The endpoint combines EFL and indeterminate EFL in the prevalence definition, but the record does not provide separate counts or explain the numerical handling of indeterminate measurements. The statistical analysis method, confidence interval method, multiplicity plan, and missing-data procedure are not reported in the registry record. Numerical findings for the secondary outcomes are also absent.
The record is marked terminated, but the reason is not reported. The available information does not establish whether all intended procedures were completed or why enrollment differed from the brief summary’s stated plan. These limitations concern what can be concluded from the registry record; they do not determine what may have been learned outside the information recorded there.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Determination of the Prevalence and Severity of Expiratory Flow Limitation in Chronic Obstructive Pulmonary Disease Patients — NCT03851510.
- Registry record last updated 2024-10-24; status last verified 2024-10.
- Results first posted 2024-10-24.
- 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 describes a non-randomized, unmasked study of EFL prevalence and related measures in people with COPD. Participants were to be screened first with the Resmon Pro and then with the Vector device; participants with EFL detected by Vector were described as eligible for a 20 minute titration procedure. The primary endpoint defines prevalence using a supine Vector DeltaXRS value greater than or equal to 2.8 and includes EFL and indeterminate EFL.
The registry lists enrollment of 57, while the brief summary describes an intended enrollment of 100. The study is marked terminated, with no reason reported. The primary endpoint result, its precision, and numerical results for the secondary outcomes are not reported in the registry record. The safety entry lists 0 participants affected by serious adverse events, 1 affected in the other adverse-event category, and 0 deaths among 57 at risk. These details support description of the registered design and recorded safety counts, but not conclusions about prevalence, treatment effects, or comparative device performance.