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 Comparing Patient Comfort and Safety Between Iodixanol and Iopamidol in Patients Undergoing Peripheral Arteriography (NCT01475097), a randomized phase 4 study. The primary outcome is Subjects Experiencing Discomfort When Undergoing Peripheral Arteriography.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01475097 |
| Phase | Phase 4 |
| Condition | Drug Safety |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 255 |
| Arms in the primary outcome | n/a |
| Lead sponsor | GE Healthcare |
| Results posted | Yes |
2. Clinical Question
Population
Patients undergoing arteriography of peripheral arteries. The registry record says 249 subjects completed assessments for overall discomfort, heat, or pain during the diagnostic phase of imaging. It records 124 subjects receiving iodixanol and 125 receiving iopamidol for those assessments. Enrollment was 255.
Intervention
Iodixanol 320 mg I/mL, described in the study summary as an iso-osmolar contrast medium. The intervention is listed as a drug. The registry record does not provide further administration details in the arm descriptions.
Comparator
Iopamidol 370 mg I/mL, described in the study summary as a low-osmolar contrast medium. It is the active comparator in a randomized, double-blind, parallel study. The registry record does not provide further administration details in the arm descriptions.
Primary question
How many subjects experienced overall discomfort, heat, or pain during the diagnostic phase of peripheral arteriography, with assessment within 10 minutes post contrast administration? The registry record identifies the comparison but does not report the category-specific outcome results needed to describe how the groups differed.
3. Trial Design
This was a Phase 4 randomized, double-blind study with a parallel-group model. The registry record lists iodixanol 320 mg I/mL and iopamidol 370 mg I/mL as the two drug interventions. Its stated purpose was to compare the overall patient comfort profile of an iso-osmolar contrast medium and a low-osmolar contrast medium in patients undergoing peripheral arteriography.
The record lists enrollment of 255 and a status of completed. The study started in 2011-10, and primary completion was recorded as 2013-02. These are registry dates; they do not by themselves describe when each participant was enrolled, treated, or assessed. The arm descriptions contain no additional details about treatment administration or procedures.
Randomization and double masking are design features, not results. Randomization is intended, in general, to allocate participants by chance and reduce systematic differences between groups at the start of a trial. Double masking is intended, in general, to limit the influence of treatment knowledge on participant experience, care, or assessment. The registry record does not describe how randomization or masking was implemented, who was masked, or whether masking was maintained.
The primary outcome concerns participants experiencing discomfort, heat, or pain during the diagnostic phase of imaging, with the timeframe stated as within 10 minutes post contrast administration. Comparison of overall image quality is listed as a secondary outcome. Although the record identifies two outcome measures, it reports no analyses. It therefore does not permit a full account of the analysis plan or of results for either outcome.
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.
Before assignment: Total of 255 subjects enrolled in this study. 2 subjects discontinued the study prior to contrast administration. Therefore, 253 subjects completed the study.
Overall Study
| Stage | Iodixanol 320mgI/mL | Iopamidol 370mgI/mL |
|---|---|---|
| STARTED | 128 | 127 |
| COMPLETED | 127 | 126 |
| NOT COMPLETED | 1 | 1 |
Reasons for not completing this period:
| Reason | Iodixanol 320mgI/mL | Iopamidol 370mgI/mL |
|---|---|---|
| Protocol Violation | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: 249 subjects completed assessments, for overall discomfort, heat or pain between Iodixanol and Iopamidol during the diagnostic phase of imaging.124 subjects received Iodixanol and 125 subjects received Iopamidol.
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 | Iodixanol 320mgI/mL | Iopamidol 370mgI/mL | Total |
|---|---|---|---|---|
| Participants analysed | 127 | 126 | 253 | |
| Age, Continuous | years | 64.5 (SD 13.34) | 62.0 (SD 15.30) | 63.2 (SD 14.38) |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 55 | 68 | 123 |
| Age, Categorical: >=65 years | Participants | 72 | 58 | 130 |
| Sex: Female, Male: Female | Participants | 49 | 45 | 94 |
| Sex: Female, Male: Male | Participants | 78 | 81 | 159 |
| Region of Enrollment: United States | participants | 27 | 24 | 51 |
| Region of Enrollment: Germany | participants | 38 | 39 | 77 |
| Region of Enrollment: Spain | participants | 57 | 58 | 115 |
| Region of Enrollment: United Kingdom | participants | 5 | 5 | 10 |
6. Primary Endpoint
The registry lists the primary outcome as Subjects Experiencing Discomfort When Undergoing Peripheral Arteriography, measured over Within 10 minutes post contrast administration..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of subjects experiencing overall discomfort, heat, or pain between iodixanol and iopamidol during the diagnostic phase of imaging. The stated assessment timeframe is within 10 minutes post contrast administration. The unit is participants, and the endpoint is recorded as a number rather than as a continuous measurement.
Such an endpoint captures whether a participant experienced any of the stated symptoms in the specified period. In general, a participant-level binary outcome can be useful when the clinical question concerns the occurrence of an event, rather than its intensity or duration. Combining several experiences into one endpoint can make the outcome more inclusive, but it also means the total does not reveal which experience occurred or how severe it was. The registry record does not report separate results for discomfort, heat, or pain, nor does it give a severity scale.
The record identifies 249 subjects who completed assessments for these experiences, including 124 receiving iodixanol and 125 receiving iopamidol. Those assessment-population figures do not supply the numbers experiencing each endpoint category. The category-specific primary results are not reported in the registry record, so the size and precision of any between-group difference cannot be described from this record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically focused comparison: patient-reported discomfort, heat, or pain around the time of contrast administration for peripheral arteriography. It gives the endpoint definition, timeframe, and assessment-population figures, but does not provide the primary outcome counts for the groups. As a result, the direction, magnitude, and precision of the primary comparison are not reported in the registry record.
For an event-count endpoint, interpretation ordinarily depends on the event count in each group and the number of participants assessed in each group. Those values permit an estimate of the difference between groups and an interval expressing uncertainty. Here, only the assessed group sizes are stated; the counts experiencing the endpoint and a comparison estimate are absent. A p-value, confidence interval, or other inferential result for the primary endpoint is also not reported in the registry record. No conclusion about which group had more or fewer reported symptoms can therefore be drawn from the record.
The record says that 249 subjects completed the assessments, with 124 receiving iodixanol and 125 receiving iopamidol. These figures describe the assessment population and should not be mistaken for outcome events. Enrollment was 255, but the record does not explain the relationship between enrollment and completion, the reasons for any uncompleted assessments, or how participants without assessments were handled in analysis. The group descriptions are not a substitute for a stated analysis population.
Overall image quality is named as a secondary outcome, but its results are not reported in the registry record. The registry record lists two outcome measures and zero analyses. It does not provide an analysis method, adjustment strategy, or inferential results for the outcomes. Consequently, it is not possible to assess whether the primary comparison was adjusted, whether secondary findings were exploratory, or how uncertainty was quantified.
General statistical context: an estimated difference is more informative when read with its confidence interval. The estimate describes the observed contrast, while the interval shows a range of values compatible with the data under the analysis assumptions. A wide interval indicates limited precision; a narrow interval indicates greater precision. Neither an estimate nor its interval establishes that a result is clinically important. In this record, the necessary primary estimate and interval are not reported, so precision cannot be assessed.
The safety counts are separate from the comfort endpoint. The registry lists serious adverse event counts and counts for other adverse events by treatment group, but these summaries do not replace the primary outcome analysis. They also do not, on their own, establish a causal explanation for an event or a comprehensive comparative safety profile. The interpretation of each safety count depends on its definition, collection period, and analysis population, details that are not fully reported in the registry record.
9. Statistical Methods Explained
The record gives several design and endpoint labels but does not report the statistical analysis methods used for the trial. The explanations below are general statistical context; they should not be read as claims about methods actually used in this study.
What does randomization contribute?
In general, random assignment is intended to make treatment groups comparable at the start of a study, on average. It can reduce the risk that participant characteristics or clinician choices determine which treatment is received. Randomization does not guarantee that the groups will be identical, particularly in a finite study. It also does not address every source of bias after assignment, such as missing outcome assessments, deviations from the assigned intervention, or differences in outcome measurement.
The registry record identifies the study as randomized but does not report the sequence-generation method, allocation concealment, or any stratification factors. It is therefore not possible to assess those implementation details from this record.
What does double masking mean?
In general, masking means keeping treatment assignment unknown to specified people involved in a trial. It may limit the effect of expectations on symptom reporting, clinical interactions, or assessment. “Double” identifies the registry’s masking category, but the record does not say which roles were masked or how masking was maintained. No conclusion about the success of masking can be made from the label alone.
How should a participant event count be understood?
The primary endpoint is expressed as a number of participants experiencing discomfort, heat, or pain. For a binary event outcome, each assessed participant is generally classified as having or not having the event under the outcome definition. The group event count and the number assessed are then needed to estimate the event frequency in each group. A comparison may be expressed in several ways, such as an absolute difference or a relative measure, but the registry record does not report a selected measure or the underlying primary event counts.
General statistical context: a confidence interval represents uncertainty around an estimate under the assumptions of the analysis. It is not a guarantee that the true value lies within the interval, nor does it show whether the estimated difference matters to patients. A p-value, when reported, addresses compatibility with a specified null model; it does not measure the size or importance of an effect. Neither measure is reported for the primary endpoint in the registry record.
What do the planning assumptions mean?
The record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It describes planning at stated fractions of the observed effect. These are assumptions for sample-size illustration, not evidence that the original trial used those assumptions to set its enrollment target. The record does not report the trial’s own sample-size justification.
General statistical context: planning calculations estimate the number of participants needed to detect a chosen effect under specified assumptions. They are not “observed power” and do not establish whether the completed study had adequate power. A planning result depends on the effect size chosen, the outcome variability or event frequency, the significance level, the allocation, and the statistical method. Because the primary event counts and planning values are not reported in the record, no trial-specific planning result can be interpreted.
The stated general calculation approach uses a normal approximation and equal allocation. An approximation can simplify planning calculations, but its suitability depends on the outcome and the data structure. For count outcomes with over-dispersion, general methods may need to account for variability greater than a simple model assumes; otherwise, uncertainty can be understated. The registry record does not say that an over-dispersion model was used, and the primary endpoint is described as participants with an event rather than as a rate of repeated events. It would be inappropriate to infer a model from the planning description.
The record distinguishes planning illustrations for time-to-event outcomes, which use a total number of events, from other illustrations, which use participants per arm. The primary endpoint is not described as time-to-event. No trial-specific sample-size illustration values are reported in the record, so this distinction provides methodological context rather than a numerical conclusion about this study.
What can be inferred from the listed analyses?
The registry record reports zero analyses. That absence does not identify which statistical tests, models, or estimands were used, if any, for the posted outcomes. The record does not report an intention-to-treat analysis, a per-protocol analysis, covariate adjustment, or a method for handling missing data. These details are important because choices about who is included and how outcomes are modeled can affect estimates and their uncertainty. Without the analysis description and outcome results, the statistical evidence cannot be independently evaluated from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists two outcome measures: the primary discomfort endpoint and a secondary comparison of overall image quality. It does not report the analyses, a prespecified hierarchy, or a method for controlling the chance of false-positive findings across multiple comparisons. Whether multiplicity adjustment was planned or used is not reported in the registry record. No inference should be made about such adjustment from the existence of a primary and a secondary outcome alone.
The primary outcome description includes overall discomfort, heat, or pain, while the registry’s skip note indicates that the primary outcome has several categories or time points and was not reduced to one comparison. Category-specific results and any separate time-point results are not reported in the registry record. Without those details, it is not possible to establish which comparisons were intended as primary or how they relate to the outcome title.
The record states that 249 subjects completed assessments and gives the receiving-group counts for those assessments. It does not explain missing assessments, reasons for missingness, or whether missingness differed between groups. The approach to missing data is not reported in the registry record. General statistical context: missing outcomes can affect an estimate if the probability of missingness is related to participant characteristics, treatment, or the unobserved outcome. The direction of any resulting bias cannot be determined without further information.
The record lists zero analyses and does not specify analysis populations. It is therefore not reported whether analyses used all randomized participants, only participants with completed assessments, or another population. The listed assessment counts should not be treated as proof of a particular analysis strategy.
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 |
|---|---|---|---|
| Iodixanol 320mgI/mL | 2 | 127 | 1.6% |
| Iopamidol 370mgI/mL | 2 | 126 | 1.6% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Iodixanol 320mgI/mL | 15 of 127 |
| Iopamidol 370mgI/mL | 3 of 126 |
Most frequent serious adverse event terms
| Event term | Organ system | Iodixanol 320mgI/mL | Iopamidol 370mgI/mL |
|---|---|---|---|
| Acute Myocardial Infarction | Cardiac disorders | 2 of 127 | 0 of 126 |
| Ventricular Fibrillation | Cardiac disorders | 0 of 127 | 1 of 126 |
| Vessel Puncture Site Hematoma | General disorders | 1 of 127 | 0 of 126 |
| Retroperitoneal Hemorrhage | Gastrointestinal disorders | 0 of 127 | 1 of 126 |
| Hypoxia | Respiratory, thoracic and mediastinal disorders | 0 of 127 | 1 of 126 |
| Hemorrhage from femoral common artery | Vascular disorders | 0 of 127 | 1 of 126 |
| Hypovolemic Shock | Vascular disorders | 0 of 127 | 1 of 126 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Iodixanol 320mgI/mL | Iopamidol 370mgI/mL |
|---|---|---|---|
| Dizziness | Nervous system disorders | 8 of 127 | 2 of 126 |
| Photopsia | Eye disorders | 7 of 127 | 1 of 126 |
Serious events with the highest arm-level rate: acute myocardial infarction (1.6%), ventricular fibrillation (0.8%), retroperitoneal hemorrhage (0.8%), hypoxia (0.8%), hemorrhage from femoral common artery (0.8%).
The registry record lists serious adverse event counts by group: 2 of 127 at risk for iodixanol 320mgI/mL, and 2 of 126 at risk for iopamidol 370mgI/mL. It also lists other adverse event counts: 15 of 127 at risk for iodixanol and 3 of 126 at risk for iopamidol. These are counts of affected participants as recorded, paired with the corresponding at-risk group sizes. They are not calculated rates or adjusted comparisons.
Serious adverse events and other adverse events are distinct categories in the record. The terms listed among the serious events are Acute Myocardial Infarction (1.6%), Ventricular Fibrillation (0.8%), Retroperitoneal Hemorrhage (0.8%), Hypoxia (0.8%), Hemorrhage from femoral common artery (0.8%), and Hypovolemic Shock (0.8%). The record does not assign those listed terms to a treatment group in the information. Deaths are not reported in the registry record.
General statistical context: adverse event counts require careful interpretation because event definitions, observation periods, severity criteria, and participant exposure can affect what is recorded. The registry record does not provide enough detail to assess those features or to determine whether events were judged related to study treatment. The counts alone do not establish causation or a comparative safety conclusion.
12. What the Result Does, and Does Not, Mean
This record establishes that a randomized, double-blind, parallel Phase 4 comparison of iodixanol and iopamidol was conducted in patients undergoing peripheral arteriography. It identifies the contrast media, the primary comfort-related endpoint, its assessment timeframe, and the number of subjects recorded as completing assessments. It also lists a secondary image-quality outcome and adverse event summaries.
It does not establish the observed primary outcome difference. The registry record does not report the numbers experiencing discomfort, heat, or pain by group, nor an effect estimate, confidence interval, or p-value. Without those results, the direction and precision of the comparison cannot be evaluated. The record also does not report the results for overall image quality.
The event counts in the safety summary describe what was recorded among the stated at-risk groups. They should not be treated as proof that an event was caused by either contrast medium or as a complete assessment of relative safety. The record does not provide the fuller event definitions, observation details, or treatment attribution needed to support such claims.
General statistical context: a non-significant test, if one were reported, would not by itself prove that two treatments are equivalent. Equivalence or non-inferiority requires an appropriate design, a prespecified margin, and an analysis suited to that question. Those details are not reported in the registry record. Likewise, a numerical difference would need to be considered with its uncertainty and clinical relevance, neither of which can be evaluated for the primary endpoint from the posted results.
Accordingly, the record supports a description of the study question and available design and safety information, but not a conclusion about comparative comfort, image quality, or overall treatment benefit. It cannot establish that one intervention is preferable, and it does not provide a basis for medical advice.
13. Why This Trial Matters Statistically
This trial is statistically interesting because its primary question concerns patient experience close to the time of contrast administration. The endpoint is not an imaging measurement alone: it counts participants reporting discomfort, heat, or pain during the diagnostic phase. That makes clear outcome definitions and consistent assessment important. The stated timeframe—within 10 minutes post contrast administration—defines when experiences are counted, but the registry record does not describe the assessment instrument or how the categories were handled.
The randomized, double-blind, parallel design is relevant to a comparison in which reported symptoms may be influenced by expectations or assessment. In general, randomization can reduce baseline confounding, while masking can limit some sources of measurement and reporting bias. The record gives those design labels but not the implementation details needed to evaluate how well those protections operated.
The statistical value of an event comparison depends on more than the number of participants assessed. The event counts, a clearly defined comparison, and an uncertainty measure are needed to judge the observed contrast. Although the record gives assessment-population figures, it does not report primary event counts or inferential results. This illustrates why enrollment and completion figures alone cannot establish what an endpoint showed.
The presence of a secondary image-quality outcome and several categories or time points also raises general questions about multiplicity and outcome selection. Without reported analyses or a stated hierarchy, readers cannot tell how those comparisons were planned or interpreted. The record’s missing analysis details therefore limit reproducibility as well as interpretation.
Finally, the safety summary demonstrates the need to separate descriptive counts from causal or comparative claims. Serious and other adverse events are listed, but the record does not provide all the context needed to interpret them as treatment effects. Together, these features make the study a useful example of the distinction between a registered design, posted descriptive information, and an analyzable result.
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 trial-specific limitation of the registry record is that it does not report category-specific results for the primary comfort endpoint. The endpoint title and assessment population are given, but the number of participants experiencing discomfort, heat, or pain in each group is not. Consequently, no primary effect estimate or measure of precision can be assessed.
The record says that the primary outcome has several categories or time points and was not reduced to one comparison. It does not provide the separate results or explain how the categories and time points were defined and analyzed. The instrument used to elicit or grade discomfort, heat, and pain is also not reported in the registry record.
The secondary outcome is identified as overall image quality, but its results are not reported in the registry record. The record lists zero analyses and does not describe the statistical methods, analysis populations, missing-data procedures, or multiplicity approach. It also does not explain how the 249 subjects who completed assessments relate to the enrollment of 255.
Implementation details for randomization and double masking are not reported in the registry record. The arm descriptions are blank, and administration procedures are not described there. The safety section provides counts and selected serious-event terms, but does not report the full context needed to evaluate event collection, timing, attribution, or comparative uncertainty. Deaths are not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Comparing Patient Comfort and Safety Between Iodixanol and Iopamidol in Patients Undergoing Peripheral Arteriography — NCT01475097.
- Registry record last updated 2014-06-11; status last verified 2014-06.
- Results first posted 2014-04-15.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT01475097 is a completed Phase 4 randomized, double-blind, parallel study sponsored by GE Healthcare. It compared iodixanol 320 mg I/mL with iopamidol 370 mg I/mL in patients undergoing peripheral arteriography. Enrollment was 255; the study started in 2011-10, and primary completion was recorded as 2013-02.
The primary endpoint concerned participants experiencing discomfort, heat, or pain during the diagnostic phase, within 10 minutes post contrast administration. The registry record says 249 subjects completed assessments, with 124 receiving iodixanol and 125 receiving iopamidol. Overall image quality was listed as a secondary outcome.
Primary outcome results, secondary outcome results, and analysis methods are not reported in the registry record. The record lists serious and other adverse event counts by group, but these descriptive figures do not provide a complete comparative safety analysis.