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 Heme Iron Polypeptide for Iron Deficiency Anemia in Chronic Renal Failure (NCT00318812), a randomized phase 2, phase 3 study. The primary outcome is Hemoglobin Concentration at 6 Months.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00318812 |
| Phase | Phase 2, Phase 3 |
| Condition | Anemia, Renal Failure |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 55 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Ottawa Hospital Research Institute |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned pre-dialysis patients with iron-deficiency anemia in the setting of chronic kidney disease. The registry lists anemia and renal failure as conditions. It describes a pilot randomized controlled study and records enrollment of 55, although the primary outcome results are reported for 18.0 participants in the Heme Iron arm and 22.0 in the Iron Sucrose arm. The registry record does not report further eligibility details or a fuller description of the participants.
Intervention
The intervention was Heme Iron Polypeptide, also named Proferrin. The arm description states 11mg PO tid for 6 months; the study summary describes the treatment as oral. The registry record does not report additional details about adherence, treatment changes, or whether participants received other iron-related care during follow-up.
Comparator
The comparison was iron sucrose, also named Venofer. Its arm description states Venofer q month IV x 6 months, and the study summary describes it as intravenous iron sucrose. Further details about administration procedures or co-interventions are not reported in the registry record.
Primary question
The primary outcome was hemoglobin concentration at 6 months, measured in g/L. The registry states that the study aimed to determine whether oral Heme Iron Polypeptide was as effective as intravenous iron sucrose for treating iron-deficiency anemia in patients with chronic kidney disease. The posted outcome consists of a median and inter-quartile range for each arm, not a reported between-arm effect estimate or an inferential test. Consequently, the posted figures describe the observed arm results but do not, on their own, establish a statistical comparison or answer an equivalence question.
3. Trial Design
The registry classifies the study as randomized, single masked, and parallel, with phases listed as Phase 2 and Phase 3. It is described in the official title as a pilot randomized controlled study in pre-dialysis patients. The record gives enrollment as 55 and lists the status as completed. The start is recorded as 2007-05 and primary completion as 2011-12. These are registry dates, rather than a complete account of recruitment, follow-up, or the timing of analysis.
Participants were assigned to Heme Iron Polypeptide or iron sucrose. The Heme Iron arm description specifies 11mg PO tid for 6 months; the Iron Sucrose description specifies Venofer q month IV x 6 months. The brief summary identifies the comparison as oral Heme Iron Polypeptide versus intravenous iron sucrose. The record does not report who was masked, how masking was maintained, the randomization sequence, or allocation concealment. Further design details, including site procedures and the handling of treatment discontinuation, are not reported in the registry record.
The primary outcome was hemoglobin concentration at 6 months, expressed in g/L and summarized by a median and inter-quartile range. Ferritin and transferrin saturation are listed as secondary outcomes. Although enrollment is recorded as 55, the primary outcome counts are 18.0 for Heme Iron and 22.0 for Iron Sucrose. The registry does not explain the difference between the enrollment figure and the outcome counts. The posted outcome record contains arm-level summaries, but no reported between-arm analysis for the primary outcome. Details of the trial's statistical plan and the rationale for its enrollment target 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.
Before assignment: 15 of the 55 patients were screen failures due to; Hgb too high/low, ferritin level too high, Vitamin B level too low,one had bypass surgery
Overall Study
| Stage | Heme Iron | Iron Sucrose |
|---|---|---|
| STARTED | 18 | 22 |
| COMPLETED | 18 | 22 |
| NOT COMPLETED | 0 | 0 |
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 | Heme Iron | Iron Sucrose | Total |
|---|---|---|---|---|
| Participants analysed | 18 | 22 | 40 | |
| Age, Continuous | years | 76 (66 to 83) | 66 (58 to 76) | 68 (63 to 77) |
| Sex: Female, Male: Female | Participants | 5 | 10 | 15 |
| Sex: Female, Male: Male | Participants | 13 | 12 | 25 |
| Region of Enrollment: Canada | participants | 18 | 22 | 40 |
6. Primary Endpoint
The registry lists the primary outcome as Hemoglobin Concentration at 6 Months, measured over 6 months.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | g/L |
| Endpoint classification | not reduced to a single comparison |
Hemoglobin concentration is the amount of hemoglobin measured in a blood sample. Hemoglobin is a central laboratory measure used to describe anemia, which makes it relevant to a study focused on iron-deficiency anemia. The registry specifies hemoglobin concentration at 6 months as the primary outcome and gives g/L as its unit. It reports a median and inter-quartile range rather than a mean and standard deviation.
In general, the median is the middle of the ordered observations, while the inter-quartile range describes the middle half of their distribution, from the first quartile to the third quartile. These summaries can be useful when the distribution is skewed or when a typical value and the spread of central observations are of interest. They do not describe every participant's result, and they do not quantify uncertainty in a between-arm contrast in the way a confidence interval would.
The endpoint was measured at 6 months, matching the treatment duration stated in both arm descriptions. The posted results give a median of 117.0 g/L, with an inter-quartile range of 110.0 to 129.0, among 18.0 participants in the Heme Iron arm. For the Iron Sucrose arm, the median is 113.0 g/L, with an inter-quartile range of 108.0 to 120.0, among 22.0 participants. The registry record does not report a baseline-adjusted endpoint, a change-from-baseline result, or a comparative estimate for this outcome.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
At 6 months, the posted median hemoglobin concentration is 117.0 g/L in the Heme Iron arm and 113.0 g/L in the Iron Sucrose arm. The corresponding inter-quartile ranges are 110.0 to 129.0 and 108.0 to 120.0. The outcome counts are 18.0 and 22.0, respectively. These are descriptive summaries of the participants with reported primary outcome values; the registry does not explain why those counts differ from the enrollment figure of 55.
The medians describe the middle of each arm's observed distribution. The inter-quartile ranges indicate that participant values varied within each arm. They are not confidence intervals for the medians and should not be interpreted as uncertainty limits for the difference between arms. The ranges overlap, but overlap or non-overlap of inter-quartile ranges is not a formal test of a treatment contrast. The registry does not report a confidence interval, p-value, or other inferential result for the primary comparison. No conclusion about statistical compatibility, equivalence, or non-inferiority can be drawn from the arm summaries alone.
The study's stated purpose was to determine whether Heme Iron Polypeptide was as effective as intravenous iron sucrose. Such a question requires a defined comparison and an analysis suited to the intended claim. A pair of medians does not itself establish equivalence: an equivalence assessment generally needs a prespecified margin and an estimate of the treatment contrast with uncertainty. The margin and such an analysis are not reported in the registry record. The record also does not report a non-inferiority margin or analysis.
Ferritin and transferrin saturation are named as secondary outcomes, but their results are not included in the posted outcome data described in the record. The record lists three outcome measures and zero analyses. The absence of a posted comparative analysis means the available numerical results support a descriptive reading only. It does not establish why an analysis is absent or whether an analysis was conducted outside the registry record.
The study is identified as a pilot and records 55 enrolled participants, while primary outcome values are available for the two arm counts stated above. These registry entries are relevant to how much information the posted summaries contain, but they do not identify the reason for missing outcome values or provide a measure of precision for a treatment contrast. The record does not report a sample-size justification or an analysis population. The careful interpretation is therefore limited to the arm-level endpoint distributions that were posted, without attributing a causal or clinical meaning to their numerical separation.
9. Statistical Methods Explained
The registry identifies a randomized, single-masked, parallel study. Randomization is a design approach intended, in general, to reduce systematic differences between treatment groups at assignment. A parallel design means that the recorded comparison has separate arms, rather than a crossover sequence described in the record. The label single masked indicates that masking was used, but the identity of the masked parties and the practical masking procedures are not reported in the registry record. The sequence-generation method and allocation concealment are also not reported in the registry record.
What do the median and inter-quartile range describe?
The primary outcome is summarized by a median and inter-quartile range. In general, the median is a measure of location: it identifies the point that divides ordered observations into lower and upper portions. The inter-quartile range spans the first and third quartiles, describing the central portion of the observed values. It is a measure of spread, not a measure of precision for a treatment effect. The registry's Heme Iron summary is a median of 117.0 g/L and an inter-quartile range of 110.0 to 129.0 among 18.0 participants. The Iron Sucrose summary is a median of 113.0 g/L and an inter-quartile range of 108.0 to 120.0 among 22.0 participants.
These summaries permit readers to compare the reported central values and distributions descriptively. They do not reveal the full set of participant observations. They also do not provide a standard error, a confidence interval for either median, or a confidence interval for a difference between arms. A confidence interval is, in general, a range of values compatible with a statistical procedure applied to the data and assumptions. It helps communicate estimation uncertainty; no such interval for the primary comparison is reported in the registry record.
What would a comparative analysis add?
A comparative analysis would estimate the contrast between the randomized arms and quantify its uncertainty. Depending on the planned estimand and distributional assumptions, methods could compare means, medians, ranks, or another defined feature of the outcome distribution. This is a general description of statistical options, not a claim about the method used in this trial. The registry does not report the planned comparative method, a comparative estimate, a p-value, or a confidence interval for hemoglobin concentration at 6 months.
The stated study aim uses the language of determining whether one treatment is as effective as another. In general, an equivalence analysis asks whether the treatment contrast is sufficiently close to zero according to a prespecified equivalence margin. A non-inferiority analysis instead assesses whether the contrast excludes an unacceptable loss according to a prespecified margin. Neither type of claim follows merely from observing similar-looking arm summaries. The registry record does not report an equivalence margin, a non-inferiority margin, or either corresponding analysis. It would therefore be inappropriate to interpret the posted medians as a formal equivalence or non-inferiority result.
Why does the outcome scale matter?
Hemoglobin is recorded as a continuous measurement in g/L. Continuous outcomes can be summarized with different measures of location and spread. Means and standard deviations describe one aspect of a distribution; medians and inter-quartile ranges describe another. In general, the choice can reflect the distribution of the data and the analysis plan. The registry specifically reports medians and inter-quartile ranges, but does not state why these summaries were selected or whether they were prespecified. The data distribution and any transformation are not reported in the registry record.
The registry lists ferritin and transferrin saturation as secondary outcomes. Their names indicate additional measures included in the outcome record, but details such as measurement timing, summary methods, and comparative results are not reported in the registry record. No inferential result for those outcomes is available in the posted results described by the record.
What can sample-size planning illustrations say?
In general, sample-size planning depends on a target effect, variability assumptions, significance level, power target, allocation, and the chosen analysis. The registry's planning illustration uses the observed effect, assumes a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the target effect defined as a stated fraction of the observed effect. These are planning illustrations based on the observed effect, not the trial's own design justification. They are not observed power and should not be read as evidence that the trial had a particular probability of detecting an effect after the results were observed. The registry record does not report the original sample-size justification, the effect targeted when the study was designed, or the assumptions used by investigators for the trial's enrollment target.
A planning calculation based on an observed effect is especially dependent on the observed estimate: the illustration changes with that estimate and does not independently establish the likely precision of a future study. The record does not provide a comparative primary effect estimate for the posted outcome, so the planning assumptions should not be mistaken for a trial finding. No participant-per-arm illustration values are stated in the registry record.
What is the role of dispersion and over-dispersion?
For a continuous outcome such as hemoglobin concentration, dispersion describes how individual observations vary around a measure of location. The inter-quartile range is the dispersion summary used in the posted primary results. Over-dispersion is a general concern in settings where observed variability exceeds what a statistical model assumes; it can make standard errors too small and uncertainty appear narrower than warranted if the model is not adapted. The registry record does not identify a model for the primary outcome, report a dispersion parameter, or indicate that over-dispersion was assessed. There is no basis in the posted record to say that over-dispersion affected this analysis.
Overall, the statistical information in the registry consists of arm-level primary outcome summaries and listed secondary outcomes. Without a reported comparative method and estimate, the results support description of the observed values but not a formal inference about the difference between treatment strategies.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists hemoglobin concentration at 6 months as the primary outcome and identifies ferritin and transferrin saturation as secondary outcomes. It records three outcome measures and zero analyses. Having multiple outcomes can create a multiplicity issue if several statistical tests are conducted and interpreted together. In general, the more opportunities there are to declare a finding, the greater the chance that at least one result may appear notable by chance. Methods such as defining a primary outcome in advance, adjusting significance thresholds, or using a hierarchical testing plan can address particular multiplicity concerns. The registry record does not report whether any such approach was planned or used.
The posted results described in the record do not include comparative analyses for the primary outcome or results for the secondary outcomes. The missing inferential information should not be taken as evidence that the outcomes were not analyzed; whether analyses were conducted outside the registry record is not reported in the registry record. The analysis plan, outcome hierarchy beyond the primary and secondary labels, and handling of multiple comparisons are not reported in the registry record.
The primary outcome counts are 18.0 for Heme Iron and 22.0 for Iron Sucrose, while enrollment is listed as 55. The record does not explain this difference. Missing outcome values can affect interpretation if the participants with observed outcomes differ systematically from those without observed outcomes. In general, analyses may use different approaches to missing data, but their validity depends on assumptions about why values are missing. The number and reasons for missing primary outcome measurements, any imputation, and any sensitivity analyses are not reported in the registry record.
The record also does not identify whether the primary result uses all randomized participants, participants who received treatment, or only participants with observed outcomes. These are distinct analysis populations in general. Without a reported population definition and missing-data handling, the arm summaries should be understood as the posted summaries, not assumed to represent a specific analysis population.
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 |
|---|---|---|---|
| Heme Iron | 0 | 18 | 0.0% |
| Iron Sucrose | 0 | 22 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 3% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Heme Iron | 5 of 18 |
| Iron Sucrose | 4 of 22 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Heme Iron | Iron Sucrose |
|---|---|---|---|
| constipation | Gastrointestinal disorders | 5 of 18 | 4 of 22 |
| abdominal cramps | Gastrointestinal disorders | 5 of 18 | 3 of 22 |
| Muscle cramps | Musculoskeletal and connective tissue disorders | 5 of 18 | 2 of 22 |
| Diarrhoea | Gastrointestinal disorders | 2 of 18 | 3 of 22 |
| Dyspepsia | Gastrointestinal disorders | 1 of 18 | 3 of 22 |
| Symptomatic Hypotension | Cardiac disorders | 0 of 18 | 3 of 22 |
| Skin Rash | Skin and subcutaneous tissue disorders | 1 of 18 | 0 of 22 |
The registry reports serious adverse events for both arms as zero affected participants: 0 of 18 at risk in Heme Iron and 0 of 22 at risk in Iron Sucrose. These are counts in the posted safety record. They describe the recorded participants and do not establish that no serious adverse events occurred outside the scope of the submitted record. The registry lists no serious adverse event terms.
Other adverse events are reported for 5 of 18 participants at risk in the Heme Iron arm and 4 of 22 at risk in the Iron Sucrose arm. The registry does not provide the event terms in the registry record for this analysis, so the types of these events cannot be characterized. Counts of participants affected are not necessarily counts of total events, since one participant may experience more than one event; whether the record's counts refer to unique participants or event occurrences is not further described.
Deaths are listed as null for both arms. This should be read as no death count reported in the registry record, not as a reported count of zero. The record does not provide detail about safety definitions, monitoring procedures, severity categories for other adverse events, or a comparative safety analysis. These arm-specific counts are descriptive and do not by themselves establish a difference between treatments.
12. What the Result Does, and Does Not, Mean
The posted primary results describe hemoglobin concentration at 6 months in the two randomized arms. The median is 117.0 g/L among 18.0 participants assigned to Heme Iron and 113.0 g/L among 22.0 participants assigned to Iron Sucrose. The inter-quartile ranges are 110.0 to 129.0 and 108.0 to 120.0, respectively. These values show the reported central tendency and middle spread for each arm. They do not show the full distributions or quantify uncertainty in a treatment contrast.
The registry's stated aim was to determine whether Heme Iron Polypeptide was as effective as intravenous iron sucrose. The posted arm summaries alone do not establish that claim. A formal assessment of equivalence or non-inferiority would require a prespecified clinical margin and a suitable analysis with uncertainty quantified; these are not reported in the registry record. Nor is a comparative test or confidence interval reported for the primary outcome. The numerical ordering of two medians cannot substitute for that inferential information.
The record identifies the trial as a pilot and reports enrollment of 55. The primary outcome summaries, however, have counts of 18.0 and 22.0. The record does not explain the difference, identify the analysis population, or describe missing outcome values. Therefore, the posted summaries should not be treated as a complete account of outcomes for every enrolled participant.
Ferritin and transferrin saturation are listed as secondary outcomes, but their results are not available in the posted outcome information. Safety counts include no participants with a reported serious adverse event in either arm, while other adverse events are recorded for 5 and 4 participants, respectively. These are descriptive safety counts, and the record does not provide a comparative analysis or the terms for those other events.
The results do not establish why the arm summaries differ, whether any apparent difference is due to treatment, or how precisely the between-arm effect is estimated. They also do not justify advice for individual patients. They describe the outcomes recorded for this study, with important inferential and reporting details absent from the registry record.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of the difference between reporting arm-level summaries and reporting a treatment comparison. The primary outcome is clearly named, measured at a specified follow-up time, and summarized with a median and inter-quartile range in each arm. Those details let readers understand what was measured and describe the reported distributions. Yet a treatment question concerns the contrast between arms, and that contrast is not accompanied by a comparative estimate or uncertainty measure in the registry record.
The study's purpose was framed as determining whether an oral treatment was as effective as an intravenous comparator. That wording makes the distinction between descriptive and equivalence evidence especially important. Similar-looking summaries do not themselves establish equivalence. In general, equivalence requires a margin defined before interpreting results and an analysis that assesses whether the plausible treatment contrast lies within that margin. The registry does not report such a margin or analysis. This illustrates why the statistical question needs to be specified, not inferred from the side-by-side arm values.
The record also highlights the importance of connecting enrollment, outcome availability, and analysis populations. Enrollment is 55, whereas the primary outcome summaries have counts of 18.0 and 22.0. Without an explanation of the difference, readers cannot determine from the record how outcome missingness was handled or which population the summaries represent. Transparent accounting of participant flow and missing data is important because it clarifies what evidence each estimate uses.
Finally, the study records secondary outcomes and safety counts, but the registry does not present comparative analyses for those outcomes. Statistical interpretation therefore depends not only on the values reported, but also on knowing the analysis plan, multiplicity approach, and uncertainty around estimates. The available record supports a careful descriptive account and illustrates the limits of drawing inferential conclusions from arm summaries alone.
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 registry record does not report the allocation sequence, concealment procedures, identity of the masked parties, or the operational details of masking. It records the study as randomized and single masked, but these labels alone do not allow evaluation of how randomization and masking were implemented. The record also does not give detailed eligibility criteria, participant characteristics, or site information.
The primary outcome is reported by arm as a median and inter-quartile range, with no comparative estimate, confidence interval, or p-value. The trial's statistical analysis plan, the method used to compare arms, and any prespecified equivalence or non-inferiority margin are not reported in the registry record. Although the stated aim concerns whether the treatments are as effective, the posted results do not include the analysis needed to assess that claim formally.
Enrollment is recorded as 55, but primary outcome counts are 18.0 and 22.0. The registry record does not explain this difference, report participant flow, specify the analysis population, or describe missing outcome values and their handling. Ferritin and transferrin saturation are listed as secondary outcomes, but their results are not available in the posted outcome information. The record lists three outcome measures and zero analyses, without clarifying whether analyses were conducted elsewhere.
The safety record reports zero participants affected by serious adverse events in each arm and other adverse events for 5 and 4 participants. It does not list serious event terms, specify the terms for other events, or report deaths as numeric counts; death values are null. Further safety definitions and comparative analyses are not reported in the registry record.
The original sample-size rationale and other design assumptions are not reported in the registry record. Planning illustrations based on an observed effect cannot replace that rationale or establish observed power. These limitations restrict what can be concluded from the posted record and make the arm-level descriptions more informative than any claim about comparative effectiveness.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Heme Iron Polypeptide for Iron Deficiency Anemia in Chronic Renal Failure — NCT00318812.
- Registry record last updated 2016-05-10; status last verified 2016-04.
- Results first posted 2014-05-02.
- 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
NCT00318812 is a completed randomized, single-masked, parallel pilot study of Heme Iron Polypeptide versus iron sucrose for iron-deficiency anemia in pre-dialysis patients with chronic kidney disease. The registry lists phases as Phase 2 and Phase 3, enrollment of 55, a start of 2007-05, and primary completion of 2011-12.
The primary outcome was hemoglobin concentration at 6 months, in g/L, summarized by median and inter-quartile range. Heme Iron had a median of 117.0 and an inter-quartile range of 110.0 to 129.0 among 18.0 participants; Iron Sucrose had a median of 113.0 and an inter-quartile range of 108.0 to 120.0 among 22.0 participants. Ferritin and transferrin saturation are listed as secondary outcomes.
The registry reports zero serious adverse events in each arm and other adverse events for 5 Heme Iron participants and 4 Iron Sucrose participants. It does not report a comparative primary analysis, the reason outcome counts differ from enrollment, or results for the secondary outcomes. Consequently, the posted results support a descriptive reading of the recorded outcomes, not a formal conclusion about equivalence or a treatment contrast.