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 Evaluation of Imaging of Peripheral Arteries by Optical Coherence Tomography and Intravascular Ultrasound Imaging (NCT03480685), a na na study. The primary outcome is Visualization of Vessel Morphology: Layered Structure.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03480685 |
| Phase | NA |
| Condition | Peripheral Artery Disease |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 12 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Avinger, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people with peripheral artery disease undergoing diagnostic imaging of peripheral arteries. The registry record lists enrollment as 12. For the layered-structure endpoint, it states that 24 imaging pairs of the 120 imaging pairs, comprising 240 images, were analyzed. Imaging pairs and images are not the same unit as participants, and the record does not explain how those images relate to individual participants or vessel segments.
Intervention
The imaging method of interest is optical coherence tomography (OCT). The stated purpose is to assess whether OCT can show vessel morphology in comparison with intravascular ultrasound (IVUS). The study is described as post-market and diagnostic; the registry record does not report further details about the imaging procedure or the equipment used.
Comparator
IVUS is the comparator imaging method. The arm description says that a vessel segment was imaged with IVUS and that the same segment was imaged with OCT. This paired description supports a within-segment comparison of images, rather than a comparison of separate treatment groups. The registry classification nevertheless lists a single-group model and no allocation.
Primary question
The primary question is whether OCT images show layered vessel structure with a mean image-quality score equivalent to or lower than the IVUS score. Scores range from 1 to 4, with lower scores indicating better image quality. The record does not report the observed mean scores, their confidence intervals, a non-inferiority margin, or whether the primary endpoint was met. The comparison's numerical result and its precision therefore cannot be assessed from the registry record.
3. Trial Design
This completed study is titled as an evaluation of optical coherence tomography and intravascular ultrasound imaging of peripheral arteries. Its official title describes a post-market, multi-vessel evaluation for diagnostic purposes. The registry lists peripheral artery disease as the condition, Avinger, Inc. as the sponsor, and enrollment of 12. Phase is recorded as not applicable. The study start date is 2018-05-24, and the primary completion date is 2018-08-01.
The brief summary calls the study a non-inferiority trial. Its stated aim is to determine the capability of OCT imaging to show vessel morphology compared with IVUS imaging. The intervention is listed as IVUS and OCT imaging. In the arm description, the same vessel segment is imaged using each modality, making the intended comparison a paired imaging comparison at the segment level.
The registry classifies the model as single group, lists no allocation, and records no masking. It also cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. These entries matter when interpreting any apparent contrast: the record does not describe assignment to separate, randomized groups. Rather, its procedural description pairs imaging modalities on the same segment.
The primary endpoint concerns visualization of layered vessel structure during diagnostic imaging, with a timeframe of up to 5 minutes during the procedures. Secondary outcomes are mean vessel diameter and total luminal area. The record lists 8 outcome measures overall, but does not supply their individual numerical results in the registry record for interpretation. It records 0 analyses. The protocol, analysis plan, sample-size justification, and details of how multiple vessels or segments were selected 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 | IVUS Imaging vs. OCT Imaging |
|---|---|
| STARTED | 12 |
| COMPLETED | 12 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Twenty-four imaging pairs of the 120 imaging pairs (240 images total) were analyzed for layered structures.
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: 120 matched IVUS and OCT images were collected along defined segments of peripheral vessels from 12 subjects.
| Characteristic | Unit | IVUS Imaging vs. OCT Imaging |
|---|---|---|
| Participants analysed | 12 | |
| Age, Continuous | years | 68 (55 to 87) |
| Sex: Female, Male: Female | Participants | 2 |
| Sex: Female, Male: Male | Participants | 10 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 |
| Race (NIH/OMB): White | Participants | 11 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Weight | kg | 82 (69 to 92) |
| Height | cm | 176.8 (167.6 to 187.9) |
| Leg of vessel accessed: Right Leg | Participants | 3 |
| Leg of vessel accessed: Left Leg | Participants | 9 |
| Vessel imaged: SFA | Percentage of Participants | 64 |
| Vessel imaged: Popliteal | Percentage of Participants | 36 |
| Mean length of target segment of vessel | cm | 24 (10 to 60) |
| Number of images containing a specific vessel characteristic to be scored: Layered Structure | Images | 24 |
| Number of images containing a specific vessel characteristic to be scored: Nonlayered Structure | Images | 104 |
| Number of images containing a specific vessel characteristic to be scored: Calcification | Images | 40 |
| Number of images containing a specific vessel characteristic to be scored: Stent Structure | Images | 21 |
| Number of images containing a specific vessel characteristic to be scored: Artifact | Images | 120 |
6. Primary Endpoint
The registry lists the primary outcome as Visualization of Vessel Morphology: Layered Structure, measured over During the diagnostic imaging procedures, up to 5 minutes.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the mean score for visualization of vessel morphology, specifically the layered structure of the vessel wall. Images are scored on a scale from 1 to 4. A score of 1 represents clear differentiation of vessel wall layers; a score of 2 represents differentiation of 3 wall layers; a score of 3 represents differentiation of 2 wall layers; and a score of 4 means no differentiation is visible. Lower values therefore indicate better image quality on this scale.
The registry description says the primary endpoint was met when the OCT mean score was equivalent to or lower than the IVUS mean score. This makes the endpoint a comparison of image quality, not a measure of patient health or clinical benefit. The stated assessment occurs during diagnostic imaging procedures, up to 5 minutes.
A mean gives a compact summary of scores, while the listed 95% confidence interval is intended to convey uncertainty around that summary. Because the score is an ordered scale, the meaning of a mean depends on how the scoring levels are interpreted. The registry record does not report the observed mean scores or their confidence intervals. It also does not report a formal equivalence or non-inferiority margin, so the operational meaning of equivalent cannot be assessed from the record alone.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a direct imaging question: whether OCT can depict layered vessel structure at least as favorably as IVUS according to the stated mean-score criterion. On the score scale, lower values correspond to better image quality. That direction is important; a higher numerical score would represent worse, not better, image quality.
However, the record does not report the OCT or IVUS mean score, either 95% confidence interval, a between-modality estimate, or a test result. It is therefore not possible to state whether OCT had a lower, equivalent, or higher mean score, or whether the primary endpoint was met. The registry's brief description of the study as non-inferiority does not substitute for the outcome data or the statistical decision rule.
The record identifies 24 imaging pairs of the 120 imaging pairs (240 images total) as analyzed for layered structures. These are imaging-level quantities. They should not be interpreted as a participant count, nor does the record explain whether the analyzed images represent all eligible segments, a selected subset, or another analysis population. The relationship among participants, vessels, segments, pairs, and images is not reported in the registry record.
The same-segment description suggests that paired image observations were intended, but the record's single-group classification and lack of allocation also caution against reading the study as a randomized comparison of two independent groups. For paired data, the statistical comparison depends on how the two images from a segment relate to one another. The record does not provide the paired differences or enough analysis detail to judge how that relationship was handled.
A confidence interval would be useful for assessing precision: a narrow interval would indicate a more precise estimate, while a wide one would leave greater uncertainty about the mean or contrast. Neither interval is reported. No numerical conclusion about the size or precision of the imaging difference is available, and the registry record does not report a formal conclusion about non-inferiority. Interpretation must therefore remain at the level of the study question and endpoint definition rather than a claim about the observed comparison.
The secondary outcomes include mean vessel diameter and total luminal area, but their results are not reported in the registry record. The record lists 8 outcome measures and 0 analyses, without the corresponding outcome values or analysis output. Consequently, the registry entries do not permit an assessment of consistency across outcomes, sensitivity to analytical choices, or the clinical relevance of any measured imaging differences.
9. Statistical Methods Explained
The registry identifies a mean as the primary summary measure and a 95% confidence interval as its dispersion measure. The endpoint is based on an image-quality score, and the comparison is described in terms of the OCT mean score relative to the IVUS mean score. The record does not give the actual estimates, intervals, or a complete statistical method for testing the stated comparison.
What does a mean describe?
In general, a mean summarizes the central level of a quantitative measurement by averaging its observed values. Here, the measurement is an image-quality score, with lower scores representing better visualization. A mean can condense observations into a single value, but it does not show the range or distribution of scores. Two sets of images can have the same mean while differing in how consistently the layers are visualized. The registry record does not report score distributions, so that aspect of image quality cannot be examined.
The score is ordered: each category represents a different level of visible vessel-wall differentiation. In general, calculating a mean from ordered categories treats the steps between categories as suitable for averaging. Whether that is a useful summary depends on the measurement and the analysis rationale. The registry record does not explain the rationale for using a mean rather than another summary, or report additional summaries that could clarify the distribution.
What does a confidence interval contribute?
In general, a confidence interval expresses uncertainty around an estimated quantity under the statistical method used. It is not a range containing every individual observation, and it does not by itself establish equivalence or non-inferiority. Its interpretation depends on the estimate, the data, and the model or calculation used. The registry specifies a 95% confidence interval for the mean, but the interval endpoints and calculation method are not reported in the registry record.
For a comparison of OCT and IVUS, the uncertainty around the contrast is especially relevant. If images are paired by vessel segment, an analysis may use the within-segment relationship; that relationship can affect the variability of the estimated contrast. In general, accounting for paired measurements differs from treating observations as independent. The registry's description says the same segment is imaged by both modalities, but it does not report the calculation used for the comparison, how pairing was represented in the analysis, or whether any clustering by participant or vessel was considered.
How should non-inferiority be assessed?
In general, a non-inferiority analysis asks whether a new method is not worse than a comparator by more than a prespecified acceptable amount. The decision depends on the direction of the outcome, the non-inferiority margin, and an appropriate estimate and uncertainty interval. For this endpoint, lower scores are better, and the registry states that an OCT mean score equivalent to or lower than the IVUS mean score meets the endpoint. Yet it does not report the margin or a formal decision rule. Without those details and the observed comparison, the term non-inferiority in the brief summary cannot establish how the claim was evaluated.
Equivalence and non-inferiority are not interchangeable in general. Equivalence usually requires evidence that a difference lies within prespecified bounds in both directions; non-inferiority focuses on excluding an unacceptable disadvantage in the specified direction. The registry uses the phrase equivalent or lower mean score, but the record does not explain whether this is shorthand for a formal statistical criterion or how equivalence was defined. It would be inappropriate to infer a margin or test from the wording alone.
What can be inferred from the study structure?
The study description pairs modalities on the same vessel segment, while the registry lists a single-group model, no allocation, and no masking. In general, paired imaging can reduce some sources of variation because the modalities assess the same segment. That does not remove all potential sources of bias: image acquisition, interpretation, selection of analyzed images, and dependence among multiple segments can still matter. The registry record does not report whether image readers were blinded to modality, how image pairs were selected, or how multiple observations from the same participant were handled.
Sample-size planning illustrations, when based on observed effects, are planning aids rather than observed power. The record's assumptions describe an illustration using a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. Those assumptions are not reported as the trial's own design justification. The record does not report a prospective sample-size rationale, and no planning illustration can replace the missing outcome estimates or establish the precision actually achieved.
Overall, the statistical information available defines the endpoint and names a summary and interval, but does not provide the results or sufficient analysis detail to reproduce or evaluate the primary comparison. Statistical test, model, handling of dependence, and non-inferiority margin are not reported in the registry record. These omissions limit both the assessment of precision and the interpretation of the stated endpoint criterion.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 8 outcome measures, including layered-structure visualization as the primary endpoint and secondary outcomes for mean vessel diameter and total luminal area. It records 0 analyses. The individual results for these outcomes are not reported in the registry record, and there is no description of how the outcome measures relate to one another or which analyses were intended to support formal conclusions.
In general, evaluating multiple outcomes can increase the chance of finding an apparently notable result by chance if each is tested separately. A prespecified hierarchy, adjustment, or other multiplicity strategy can help clarify how evidence across outcomes should be interpreted. The registry record does not report a multiplicity plan. Because outcome estimates and tests are absent, it is also not possible to assess whether multiplicity affected any reported inference.
The record identifies 24 imaging pairs of the 120 imaging pairs (240 images total) as analyzed for layered structures. That identifies an image-analysis population for the primary endpoint, but does not state how the analyzed pairs were selected or why other pairs were not included. The reasons for any exclusions, the handling of incomplete or uninterpretable images, and any missing-data methods are not reported in the registry record.
The registry enrollment is 12, while the endpoint description uses imaging pairs and images as its analysis units. The record does not explain the mapping between these quantities or provide participant-level analysis populations. It is therefore not possible to determine from the registry record how many participants contributed to each outcome, whether all enrolled participants contributed usable images, or how repeated segments were treated. Such details matter because multiple images from the same participant may not represent independent observations.
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 |
|---|---|---|---|
| IVUS Imaging | 0 | 12 | 0.0% |
| OCT Imaging | 0 | 12 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| IVUS Imaging | 0 of 12 |
| OCT Imaging | 0 of 12 |
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 |
|---|---|
| IVUS Imaging | 0 of 12 |
| OCT Imaging | 0 of 12 |
The safety record lists IVUS Imaging and OCT Imaging separately. For each listed group, 12 are shown at risk for serious events and 0 are shown as affected; the figures for other events are also 12 at risk and 0 affected. Deaths are recorded as 0 in each group, and no top serious-event terms are listed.
These are registry counts, not evidence that the modalities have no risk. A zero count means no event was recorded in the listed category and group in this record; it does not establish that an event cannot occur or that risk is absent. The record does not provide further event definitions, follow-up detail, or an explanation of how safety surveillance was conducted.
The two entries should not be added together to infer a total participant count. The study description says the same vessel segment was imaged by both modalities, and the registry does not explain whether the safety groups represent separate people or modality-specific exposure records for the same study population. The serious and other event counts are therefore best read as reported for each listed imaging group, without treating the groups as independent cohorts.
12. What the Result Does, and Does Not, Mean
This study addresses a diagnostic imaging question: how OCT compares with IVUS for visualizing layered peripheral artery structure. Its primary score has a defined direction, with lower values corresponding to better image quality, and the stated endpoint criterion calls for an OCT mean score equivalent to or lower than the IVUS mean score. The record also describes imaging the same vessel segment with both modalities.
What the record does not establish is the observed performance of either modality. The mean scores, 95% confidence intervals, comparative estimate, and formal endpoint conclusion are not reported in the registry record. The phrase non-inferiority in the brief summary states the study's aim, not the outcome. Without the results and the decision rule, it is not possible to conclude whether the primary criterion was met or how precisely the comparison was estimated.
The record's imaging counts describe an analysis of pairs and images, not a substitute for participant-level outcome reporting. It does not explain the selection of the analyzed images, missing or unusable images, or dependence among images from the same participant or vessel. The single-group classification, absence of allocation, and lack of masking also mean that the study should not be described as a randomized comparison of independent groups.
The registry entries do not establish that one imaging method improves patient outcomes, changes care, or is preferable for every diagnostic purpose. The primary endpoint concerns image appearance, and secondary outcomes concern vessel measurements. No clinical outcomes or numerical results for those measures are reported in the registry record. The interpretation should therefore remain limited to the study's diagnostic imaging objective, stated measurement, and unreported comparative results.
13. Why This Trial Matters Statistically
This study is statistically interesting because it puts the comparison at the image and vessel-segment level. The description says both imaging methods were used on the same segment. In general, paired comparisons can be informative because each modality is assessed against the same anatomical segment, but valid uncertainty estimates depend on recognizing that paired structure. The registry record does not report how the paired data were analyzed.
The endpoint also illustrates an important distinction between a descriptive score and a formal non-inferiority conclusion. The score has an explicit direction: a lower value means better image quality. But non-inferiority requires more than knowing the direction. In general, it needs a prespecified margin, a suitable comparison estimate, and uncertainty evaluated against that margin. The record does not report the margin or the observed result, so the stated study aim cannot be translated into a statistical conclusion.
Another relevant issue is the difference between participant counts and image counts. The record lists enrollment of 12 while describing 24 imaging pairs of the 120 imaging pairs (240 images total) analyzed for layered structures. These units serve different purposes. Without a clear account of how participants, segments, pairs, and images correspond, readers cannot determine the effective analysis population or how repeated observations might affect precision.
Finally, the registry distinguishes the study's procedural comparison from a randomized control design: allocation is listed as none, and the model is single group. This is important context for interpreting the comparison and its potential limitations. The record defines a question and a scoring approach, but its statistical value for judging the actual imaging contrast is constrained by the absence of estimates, uncertainty intervals, and analysis details.
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 record is that it does not report the primary outcome values. Although the registry identifies a mean score and 95% confidence interval, neither the OCT nor IVUS estimate nor the interval is available in the registry record for this analysis. The primary endpoint's status is also not reported in the registry record. As a result, the numerical comparison and its precision cannot be evaluated.
The record describes a non-inferiority aim but does not report a non-inferiority margin, formal hypothesis, test, or decision rule. It also does not describe the method used to calculate the confidence interval or account for the paired imaging design. These are essential details for assessing whether an endpoint criterion was met and how robust that assessment might be.
Although the same vessel segment is described as imaged with both modalities, the registry classification is single group and allocation is none. The record does not report masking, and masking is listed as none. It does not explain image-reader procedures, image selection, handling of repeat segments, or whether observations were clustered by participant. Such details could affect interpretation of image-quality scoring and statistical precision.
The endpoint population is stated in imaging pairs and images, whereas enrollment is stated in participants. The record does not explain the relationship among those units, why 24 imaging pairs of the 120 imaging pairs were analyzed for layered structures, or how missing or unusable images were handled. The protocol, sample-size justification, and complete analysis population are not reported in the registry record. Secondary outcome values are also unavailable, limiting assessment beyond the primary imaging question.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of Imaging of Peripheral Arteries by Optical Coherence Tomography and Intravascular Ultrasound Imaging — NCT03480685.
- Registry record last updated 2021-06-14; status last verified 2021-06.
- Results first posted 2021-06-14.
- 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 a completed, post-market diagnostic imaging study of OCT and IVUS for peripheral artery morphology in people with peripheral artery disease. It lists Avinger, Inc. as sponsor, enrollment of 12, a single-group model, no allocation, and no masking. The same vessel segment is described as imaged with both modalities.
The primary endpoint is a mean score for layered vessel structure, scored from 1 to 4, with lower scores indicating better image quality. The stated criterion is an OCT mean score equivalent to or lower than the IVUS mean score. The record identifies 24 imaging pairs of the 120 imaging pairs (240 images total) as analyzed for layered structures. It lists secondary outcomes for mean vessel diameter and total luminal area, 8 outcome measures, and 0 analyses.
Numerical primary and secondary outcome results, confidence-interval endpoints, the non-inferiority margin, and analysis details are not reported in the registry record. Safety entries list 0 serious events, 0 other events, and 0 deaths in each modality group.