Open Label, Randomized Study of Low Concentration Ioforminol Injections for Use in Abdominal CECT in Healthy Volunteers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Open Label, Randomized Study of Low Concentration Ioforminol Injections for Use in Abdominal CECT in Healthy Volunteers (NCT01672996), a randomized phase 1, phase 2 study. The primary outcome is Radiographic Densities at Selected Regions in Contrast-enhanced CT Examination by Location (Abdominal Aorta), kVp 80 and Contrast Type (Ioforminol vs Iopamidol), Concentration (Ioforminol 160 or 200) and Dose Levels (1.0, 1.5, and 2.0mL/kg)..

2. Clinical Question

3. Trial Design

The registry describes a phase 1/2, randomized, open-label study with a parallel-group model. Masking is listed as none. The study recruited healthy volunteers and had a planned enrollment of 66. Its stated purpose was to optimize ioforminol concentration and dose for contrast-enhanced abdominal CT, and to evaluate the safety and tolerability of low-concentration ioforminol injections. Iopamidol was also included as a contrast-agent comparator.

The intervention descriptions specify a single administration in each arm. The ioforminol regimens represented in the posted primary endpoint results combine two concentrations, 160 mgI/mL and 200 mgI/mL, with dose levels of 1.0, 1.5, and 2.0 mL/kg. The listed iopamidol regimen is 300 mgI/mL at 1.0 mL/kg. Thus, the posted results do not form a complete set of matched concentration-and-dose combinations across the two agents.

The endpoint record states that 33 subjects were evaluated using 80 kVp. Outcome entries give group sizes of 5 for each of the ioforminol concentration-and-dose combinations and 3 for the listed iopamidol regimen. The reason these endpoint group counts do not account for all 66 enrolled participants is not reported in the registry record. The randomization procedure, allocation ratio, and any sequence or concealment procedures are also not reported in the registry record.

The registry lists a study start in 2012-07, primary completion in 2012-08, and status as completed. It describes treatment-emergent adverse events as a secondary safety outcome. A detailed protocol, rationale for the chosen enrollment, planned analysis methods, and participant flow by randomized arm 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

Analysis population for the primary outcome, as defined in the registry: Evaluted 33 subjects using 80 kilovolt peak (kVp), a measure of the maximum electrical potential in kilovolts across an x-ray.

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.

Only the first 6 of 8 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Radiographic Densities at Selected Regions in Contrast-enhanced CT Examination by Location (Abdominal Aorta), kVp 80 and Contrast Type (Ioforminol vs Iopamidol), Concentration (Ioforminol 160 or 200) and Dose Levels (1.0, 1.5, and 2.0mL/kg)., measured over Within 5 minutes after administration for either Ioforminol or Iopamidol..

The primary endpoint is mean radiographic density in Hounsfield Units at the abdominal aorta at the level of the celiac artery. It was measured on contrast-enhanced abdominal CT within 5 minutes after administration. The record identifies 80 kVp imaging and describes the value as a quantitative measure of contrast attenuation: greater attenuation corresponds to a higher HU measurement.

HU provides a quantitative imaging measurement that can be summarized across participants within a regimen. Reporting a mean describes the group’s average recorded density, while the standard deviation describes the spread of individual measurements around that mean. These summaries help characterize the observed imaging values under the specific concentration and dose conditions used.

The endpoint is relevant to the stated aim of optimizing contrast concentration and dose because it records radiographic density at a specified anatomical location and time after injection. However, the numerical endpoint alone does not establish how a value relates to diagnostic accuracy or patient outcomes. This study enrolled healthy volunteers, and the registry’s endpoint description does not state a threshold for adequate imaging, a clinically meaningful difference, or a formal criterion for choosing an optimal regimen. Those criteria are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

For a continuous endpoint such as HU, a group mean is the arithmetic average of the measured values in that group. It gives a concise description of the group’s central value, but it does not show every participant’s measurement. The standard deviation (SD) describes how dispersed the individual values are around the mean. A larger SD indicates more variation among the observations; it is not the uncertainty of the mean itself. Here, the posted summaries include a mean and SD for each listed regimen, with the group size reported alongside them.

Small group sizes matter when interpreting both means and SDs. With few observations, a group mean can be sensitive to the measurements of individual participants. The observed SD still describes variation among the recorded participants, but it does not by itself indicate how precisely the group mean estimates a broader population value. The registry record does not provide confidence intervals for the means. In general, a confidence interval expresses the uncertainty associated with an estimate under a specified statistical method; it is not reported for this endpoint in the registry record.

What does the endpoint summarize?

The endpoint is radiographic density at a specified abdominal-aorta location, measured within 5 minutes after administration. The record identifies the measurement unit as HU and the imaging voltage as 80 kVp. Results are separated by contrast agent, concentration, and dose where those combinations are posted. Reading each summary as a description of its own regimen avoids treating distinct groups as if they had received identical conditions.

Randomization can support comparisons by reducing systematic differences between groups in expectation, but the record does not report the assignment procedure or allocation ratio. More importantly, randomized assignment alone does not supply a statistical estimate of a treatment contrast. A contrast estimate would quantify the difference between specified groups, while an uncertainty measure would indicate the precision of that estimate. Neither formal contrasts nor their uncertainty are reported in the registry record.

Why is over-dispersion relevant?

Over-dispersion is a general statistical concern when observed variability is greater than a model assumes. If a model assumes observations vary less than they actually do, its uncertainty estimates may be too narrow and inferential results may be overly confident. The endpoint is continuous and the registry presents group means and SDs; it does not report a model, an over-dispersion assessment, or a formal inferential analysis. The concept is therefore general context rather than a claim that over-dispersion was detected in this study.

Different statistical approaches can be appropriate for continuous outcomes, depending on the design, distribution of measurements, and intended comparison. For example, an analysis might estimate group means or contrasts and their uncertainty, with adjustments if prespecified design features require them. The registry record does not state which such methods were planned or used. It does not report whether the analysis adjusted for covariates, accounted for multiple comparisons, or assessed distributional assumptions. Those details should not be inferred from the descriptive summaries.

What can the posted summaries support?

They support description of the reported group sizes, means, and SDs. They also permit a reader to see the observed distribution of central values across the listed regimens without treating those values as inferential evidence. They do not support a conclusion that one regimen is statistically superior, equivalent, or non-inferior to another. No p-values, confidence intervals, prespecified decision margins, or formal comparison results are reported in the registry record.

The record lists no posted analyses for the primary endpoint. Consequently, the interpretation should distinguish the trial’s design from the results actually reported: randomization is a design feature, whereas a randomized comparison still requires an analysis that states the groups being compared and quantifies uncertainty. The registry does not provide that analysis. Any interpretation should therefore remain descriptive and specific to the observed groups.

Planning calculations are a separate statistical task from analyzing observed outcomes. The posted planning illustration assumptions describe two-sided significance level 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence about the results. The trial’s own sample-size justification is not reported in the registry record. No planning sample-size results are included in the registry information, so no number of participants needed for a future study can be inferred from these endpoint summaries alone.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Arm 1 - Ioforminol 160mgI/mL-1.0mL/kg", "Arm 1 - Ioforminol 160mgI/mL-1.5mL/Kg", "Arm 1 - Ioforminol 160mgI/mL-2.0mL/Kg", "Arm 2 - Ioforminol 200mgI/mL-1.0mL/kg", "Arm 2 - Ioforminol 200mgI/mL-1.5mL/kg", "Arm 2 - Ioforminol 200mgI/mL-2.0mL/Kg")
n   <- c(5, 5, 5, 5, 5, 5)
m   <- c(168, 261, 345, 341, 357, 365)
sp  <- c(41, 56.5, 30.7, 33.6, 30.1, 67.7)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Arm 1 - Ioforminol 160mgI/mL-1.0mL/kg  5  168.000  41.000  117.092  218.908
CARM  Arm 1 - Ioforminol 160mgI/mL-1.5mL/Kg  5  261.000  56.500  190.846  331.154
CARM  Arm 1 - Ioforminol 160mgI/mL-2.0mL/Kg  5  345.000  30.700  306.881  383.119
CARM  Arm 2 - Ioforminol 200mgI/mL-1.0mL/kg  5  341.000  33.600  299.280  382.720
CARM  Arm 2 - Ioforminol 200mgI/mL-1.5mL/kg  5  357.000  30.100  319.626  394.374
CARM  Arm 2 - Ioforminol 200mgI/mL-2.0mL/Kg  5  365.000  67.700  280.939  449.061

11. Multiplicity, Missing Data and Analysis Populations

The endpoint record describes density by location, imaging voltage, contrast type, concentration, and dose. The posted results span several ioforminol regimens and one iopamidol regimen. Multiple possible comparisons arise when many concentrations, doses, or endpoints are examined. A prespecified analysis plan ordinarily clarifies which comparisons are primary and how uncertainty is handled across them. A multiplicity strategy, hierarchy of comparisons, and prespecified statistical plan are not reported in the registry record. No multiplicity-adjusted results are posted.

The registry lists one secondary outcome: overall safety evaluated by recording treatment-emergent adverse events. It does not describe how missing endpoint observations were handled, whether any participants were excluded from analysis, or the criteria used to define evaluability. The reason the record identifies 33 subjects as evaluated for the primary endpoint, compared with enrollment of 66, is not reported in the registry record. The analysis population and participant flow are also not reported.

Missing-data methods matter because the interpretation of an average can depend on which participants contributed measurements and why others may not have contributed. The record does not state whether missing measurements occurred, whether any data were imputed, or whether analyses used a particular missing-data assumption. These details cannot be reconstructed from the reported group summaries. The numbers should therefore be understood as summaries of the listed endpoint groups, with the underlying analysis population not fully described.

There is no basis in the registry record for assuming that an unreported analysis was prespecified, that missing values were absent, or that the posted summaries represent every randomized participant. Those design and analysis details are not reported in the registry record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The safety outcome is described as treatment-emergent adverse events. For each listed regimen, the registry reports the number at risk for serious events and the number affected. The serious-event counts are 0 for all posted groups: 0 of 10 for each of the six ioforminol concentration-and-dose groups, and 0 of 6 for the listed iopamidol group. These are counts within the safety groups reported in the registry.

A count of 0 affected participants in a group means no serious adverse event was recorded for that group in the posted results. It does not establish that the risk is zero, particularly when the group sizes are limited. These are descriptive safety counts, not a statistical comparison between agents or dose levels. The registry does not report confidence intervals or inferential comparisons for serious events.

The death values are not populated in the record, so deaths are not reported in the registry record. The record also lists other adverse-event counts, but the serious-event figures should not be read as covering every adverse event. The safety summaries do not by themselves establish comparative safety across the regimens.

13. What the Result Does, and Does Not, Mean

The results describe mean abdominal-aorta HU measurements within 5 minutes after single administrations of the listed contrast regimens, together with SDs and group sizes. They provide a quantitative account of observed radiographic density in the healthy-volunteer groups that contributed to the posted endpoint. The safety record also gives serious adverse-event counts for the listed groups.

The summaries do not establish that any regimen works or fails, and they do not establish a preferred concentration or dose. The registry does not report a diagnostic-performance threshold, a clinically meaningful difference in HU, or a formal optimization criterion. A higher HU measurement is described as greater contrast attenuation, but the clinical implications of a particular group mean are not specified in the registry record.

The summaries do not show whether differences among group means are statistically reliable. There are no posted confidence intervals, p-values, or formal between-group estimates. The sample sizes are small, and the endpoint record identifies 33 evaluated subjects despite enrollment of 66; the reason for that difference is not reported in the registry record. These details limit conclusions about precision and representativeness.

The listed comparator results also cover only iopamidol 300 mgI/mL at 1.0 mL/kg. They do not provide a complete comparison across all dose levels used for ioforminol. Consequently, the results cannot establish relative performance across unreported iopamidol dose conditions or support a full agent-by-dose comparison.

Finally, the study population was healthy volunteers. The posted information does not establish how the observed imaging measurements would apply to patients undergoing clinical imaging or how they relate to diagnostic decisions. The registry record supports a descriptive reading of the reported measurements and safety counts, not a broader clinical conclusion.

14. Why This Trial Matters Statistically

This trial is statistically interesting because it reports a continuous imaging endpoint across several combinations of concentration and dose, rather than a single summary for one regimen. That structure makes it important to keep the comparisons specific: a result belongs to a particular agent, concentration, and dose, and should not be interpreted as if all groups differed in only one feature. The posted iopamidol result covers one dose condition, while the ioforminol summaries cover multiple conditions.

The record also illustrates the distinction between a trial design and a statistical result. Randomization is reported, but no formal analyses are posted for the primary endpoint. Descriptive group means and SDs are useful for characterizing observed measurements; they do not substitute for estimated contrasts and uncertainty when the question is comparative. Without those inferential results, the numerical pattern should not be treated as a tested ranking of regimens.

Small group sizes and incomplete reporting of the endpoint population make precision and representativeness especially important considerations. The record states enrollment of 66 and evaluation of 33 subjects for the primary endpoint, without explaining the difference. That gap highlights why participant flow and analysis-population definitions are essential parts of interpreting trial results, not just administrative details.

For researchers, the record underscores the value of reporting a prespecified comparison plan, confidence intervals, missing-data handling, and the rationale for the chosen sample size. The registry provides enough information to describe the endpoint and the reported group summaries, but not to reconstruct those elements. Its statistical contribution is therefore chiefly descriptive.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several limitations arise from the specific registry information. Although total enrollment is listed as 66, the primary endpoint description says 33 subjects were evaluated. The registry does not explain the difference, provide participant flow by arm, or identify the analysis population. The endpoint group sizes are small, including 3 participants for the posted iopamidol regimen, so the summaries offer limited information about variability and precision.

The agent regimens are not represented across the same dose conditions in the posted primary results. Ioforminol is listed at two concentrations and three dose levels, while iopamidol is listed at one concentration and one dose level. This limits the scope of direct descriptive comparisons and leaves other dose conditions unreported in the registry record.

No confidence intervals, hypothesis tests, or formal endpoint comparisons are reported. The record does not describe the randomization procedure, allocation ratio, sample-size justification, statistical analysis plan, multiplicity approach, or missing-data methods. It also does not state whether any endpoint measurements were excluded or why the evaluated population differs from enrollment.

The study recruited healthy volunteers, and the endpoint is a radiographic measurement at a defined anatomical location and time. The registry does not provide a threshold for adequate imaging or relate the measurements to diagnostic performance. These limitations constrain interpretation to the reported imaging summaries and safety counts; broader conclusions are not supported by the registry information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Open Label, Randomized Study of Low Concentration Ioforminol Injections for Use in Abdominal CECT in Healthy Volunteers — NCT01672996.
• Registry record last updated 2014-05-29; status last verified 2014-04.
• Results first posted 2014-03-03.
• 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.

19. Record Summary

NCT01672996 is a completed phase 1/2 randomized, open-label, parallel study in healthy volunteers, sponsored by GE Healthcare. It was intended to optimize ioforminol concentration and dose for contrast-enhanced abdominal CT and to assess safety and tolerability. The registry lists enrollment of 66, a study start in 2012-07, and primary completion in 2012-08.

The primary endpoint is mean radiographic density in HU at the abdominal aorta near the celiac artery, measured within 5 minutes after administration using 80 kVp imaging. Posted results include ioforminol 160 mgI/mL and 200 mgI/mL at 1.0, 1.5, and 2.0 mL/kg, and iopamidol 300 mgI/mL at 1.0 mL/kg. The registry reports group means, SDs, and group sizes, along with serious adverse-event counts.

Formal primary-endpoint analyses, confidence intervals, sample-size justification, participant flow, and details of missing-data handling are not reported in the registry record. The posted results are descriptive and do not establish a statistical or clinical ranking of regimens.