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 A Trial Comparing Ferumoxytol With Placebo for the Treatment of Iron Deficiency Anemia (NCT01114139), a randomized phase 3 study. The primary outcome is Participants Who Achieved A ≥2.0 g/dL Increase In Hemoglobin At Any Time From Baseline To Week 5.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01114139 |
| Phase | Phase 3 |
| Condition | Iron Deficiency Anemia |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 812 |
| Arms in the primary outcome | n/a |
| Lead sponsor | AMAG Pharmaceuticals, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerned people with iron deficiency anemia. The primary analysis population is described as the intent-to-treat population: randomized participants who had any exposure to ferumoxytol or placebo, analyzed according to randomized treatment assignment. The record does not give further eligibility details or a demographic description of the participants.
Intervention
Participants assigned to ferumoxytol received two intravenous doses of 510 milligrams. The first dose was given on Day 1 at baseline, and the second was given 2 to 8 (5±3) days after the first. The total cumulative dose was 1.02 grams.
Comparator
Participants assigned to placebo received two intravenous saline doses. The first was given on Day 1 at baseline, and the second was given 2 to 8 (5±3) days after the first. The listed volume for each dose was 17 mL.
Primary question
The primary endpoint counted participants who achieved an increase in hemoglobin of at least 2.0 g/dL at any time from baseline through Week 5. The registry record gives the endpoint definition, but the primary outcome counts and a single comparison between treatment groups are not reported in the registry record.
3. Trial Design
This was a Phase III, randomized, double-blind, placebo-controlled, parallel-group trial. The registry record lists an enrollment of 812 and identifies iron deficiency anemia as the condition studied. AMAG Pharmaceuticals, Inc. is listed as the sponsor. The study status is completed, with a start date of 2010-06-19 and a primary completion date of 2012-02-27.
Participants were assigned to ferumoxytol or placebo. The active-treatment description specifies two intravenous 510 milligram doses, with the second dose given 2 to 8 (5±3) days after the first. The placebo description specifies two intravenous saline doses on a similar schedule. Both arms therefore had two scheduled administrations, according to the registry descriptions.
Randomization is intended to create comparable groups on average, while masking is intended to limit the influence of treatment knowledge on participant experience, clinical care, and assessment. These are general design concepts; the registry record does not describe the randomization procedure, allocation concealment, or who was masked beyond identifying the study as double-blind.
The primary endpoint was assessed from baseline through Week 5. The registry record also lists secondary outcomes concerning hemoglobin, transferrin saturation, FACIT-Fatigue score, and time to a specified hemoglobin increase or level. The protocol details, visit schedule beyond the endpoint description, and statistical analysis plan 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 | Ferumoxytol | Placebo |
|---|---|---|
| STARTED | 609 | 203 |
| Received at Least 1 Dose of Study Drug | 608 | 200 |
| COMPLETED | 569 | 187 |
| NOT COMPLETED | 40 | 16 |
Reasons for not completing this period:
| Reason | Ferumoxytol | Placebo |
|---|---|---|
| Adverse Event | 3 | 2 |
| Lost to Follow-up | 15 | 3 |
| Withdrawal by Subject | 17 | 6 |
| Other-Missed 1 visit | 1 | 0 |
| Other-Protocol Violation | 1 | 0 |
| Other-Out of window for study drug dose | 1 | 0 |
| Other-Participant falsified records | 0 | 1 |
| Other-Participant went on hospice | 0 | 1 |
| Other-Physician changed treatment | 1 | 0 |
| Other-Withdrew prior to receiving dose | 1 | 3 |
Analysis population for the primary outcome, as defined in the registry: Intent-To-Treat (ITT) Population: Any randomized participant who had any exposure to study drug (ferumoxytol or placebo) and was based upon randomized treatment assignment.
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: Intent-To-Treat (ITT) Population: Any randomized participant who had any exposure to study drug (ferumoxytol or placebo) and was based upon randomized treatment assignment.
| Characteristic | Unit | Ferumoxytol | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 608 | 200 | 808 | |
| Age, Continuous | years | 44.8 (SD 13.82) | 46.0 (SD 13.58) | 45.1 (SD 13.76) |
| Sex: Female, Male: Female | Participants | 542 | 178 | 720 |
| Sex: Female, Male: Male | Participants | 66 | 22 | 88 |
6. Primary Endpoint
The registry lists the primary outcome as Participants Who Achieved A ≥2.0 g/dL Increase In Hemoglobin At Any Time From Baseline To Week 5, measured over Baseline (Day 1) through Week 5.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is a binary participant-level outcome: whether a participant achieved a hemoglobin increase of at least 2.0 g/dL at any post-baseline visit through Week 5. The record defines the change as the hemoglobin value at a post-baseline visit minus the baseline value. Baseline was the Day 1 value before study drug injection; when Day 1 information was missing, the screening value or most recent value before Day 1 was used.
This endpoint reduces repeated hemoglobin measurements over the specified period to an achieved/not-achieved classification for each participant. As a general statistical concept, a binary endpoint can make the clinical event being counted straightforward to describe, but it discards information about the size and timing of changes that do not meet the threshold. The registry record also states that participants without post-baseline hemoglobin values were classified as not achieving the threshold.
The endpoint is restricted to data through Week 5. It should not be interpreted as a measure of longer-term hemoglobin response. The registry record gives the endpoint definition and analysis population but does not report the group counts or a single treatment-effect estimate for this endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The trial record identifies a defined randomized comparison: intravenous ferumoxytol versus intravenous saline placebo in people with iron deficiency anemia. Its primary endpoint asks whether participants achieved a hemoglobin increase of at least 2.0 g/dL at any time from baseline through Week 5. That definition establishes what was to be counted, but it is not itself evidence about how often the endpoint occurred in either group.
The registry record does not report the primary outcome counts or a single comparison between the groups. It therefore does not support a numerical estimate of the difference in endpoint frequency, nor an assessment of the precision of such an estimate. A confidence interval, if reported with an effect estimate, would describe the range of values compatible with the data under the statistical method used; no primary-endpoint confidence interval is reported in the registry record. The record also does not report a primary-endpoint p-value.
This distinction matters because the study design and endpoint definition answer different questions from the results. Randomization and masking describe how the comparison was structured. The endpoint definition describes what counted as an event. Neither supplies the missing observed group results. Without those results, the posted record cannot establish the direction or magnitude of the primary comparison.
The listed secondary outcomes include mean change in hemoglobin, attainment of a hemoglobin level of at least 12.0 g/dL, mean change in transferrin saturation, mean change in FACIT-Fatigue score, and time to a specified hemoglobin response. These provide additional outcome definitions, but the registry record does not give their result estimates in the registry record for this analysis. They should not be treated as substitutes for the primary endpoint result.
The adverse-event information is separate from the primary efficacy endpoint. The record lists serious adverse event counts and counts for other adverse events by arm, as well as several serious adverse event terms. These figures describe events recorded in the safety information, not the primary hemoglobin outcome. They do not by themselves establish a causal relationship between treatment and an event.
In short, the posted information describes the design, treatment schedules, endpoint, and some safety counts. It does not report the primary outcome comparison needed to quantify the endpoint result. Any interpretation of treatment effect or precision would go beyond what is reported in the registry record.
9. Statistical Methods Explained
The statistical information available for this trial is limited. The registry record identifies a randomized, double-blind, parallel-group design and defines the primary endpoint and analysis population. It does not report the full statistical analysis plan, a primary treatment-effect estimate, or a confidence interval for that endpoint. The concepts below are general explanations of how such methods are commonly understood, not claims about unreported procedures in this trial.
What does a binary endpoint represent?
The primary outcome classifies each participant as having or not having achieved the specified hemoglobin increase during the assessment period. The endpoint is based on whether any qualifying post-baseline measurement through Week 5 met the threshold. As a general concept, this approach is useful when the question concerns whether a prespecified event occurred. It also compresses a series of measurements into one category, so it does not convey the full pattern of hemoglobin values or the size of a response below the threshold.
What does randomization contribute?
In general, random assignment is used to reduce systematic differences between groups at the point of allocation. It supports a fair comparison when the assigned groups are analyzed appropriately and follow-up and outcome assessment are handled consistently. The record labels the trial randomized, but the method used to generate the allocation sequence and conceal assignments is not reported in the registry record.
What does double masking mean?
Double masking indicates that more than one party involved in the trial was kept unaware of treatment assignment, but the registry record does not specify which parties. In general, masking can reduce the risk that knowledge of assignment affects behavior, co-interventions, or outcome assessment. The record does not provide further detail about masking procedures or whether masking was maintained throughout follow-up.
How should the endpoint definition be read?
The baseline value was the Day 1 measurement before injection. If that measurement was missing, the screening or most recent pre-Day 1 value was used. The calculation compared a post-baseline value with baseline, and any post-baseline visit up to and including Week 5 could qualify. Participants with no post-baseline hemoglobin measurements were classified as not achieving the increase. These rules describe how the registry defined the endpoint and handled this particular missing-measurement situation.
What would an effect estimate and confidence interval add?
As a general statistical concept, an effect estimate would summarize the observed contrast between the treatment groups for the endpoint. A confidence interval would communicate the uncertainty around that estimate under the method used. It is not a guarantee that the true effect lies within the interval, and its interpretation depends on the statistical model and assumptions. Neither the estimate nor its confidence interval is reported for the primary endpoint in the registry record.
Why can event counts be analyzed in different ways?
For a binary outcome, analyses may compare the proportions or counts in each group using a chosen effect measure and method. The analysis plan should specify the measure, handling of missing observations, and any adjustment for design features. The registry record does not report these details for the primary comparison. No unadjusted recalculation is available from the primary outcome information because the group-level endpoint counts are not reported.
What does statistical significance tell a reader?
In general, a p-value measures how unusual the observed data, or data more extreme, would be under a specified null model and its assumptions. It does not measure the probability that a treatment is effective, and it does not express the size or practical importance of an effect. A p-value for the primary endpoint is not reported in the registry record, so no statistical-significance conclusion can be drawn from the available primary outcome information.
Why do assumptions matter?
Every statistical analysis depends on assumptions, such as how observations are distributed or how missing values are treated. For example, over-dispersion is a general concern when variability in count data exceeds what a simple model assumes; accounting for it can affect uncertainty estimates. The registry entries do not establish that an over-dispersed model was used or that it was relevant to the trial analysis. The statistical model and diagnostics are not reported in the registry record.
The record notes one analysis and six outcome measures, but does not provide enough information to reconstruct the primary analysis or assess its assumptions. The sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. This is a planning framework, not observed power; the calculation results and the trial's own design justification are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists the primary endpoint and five secondary outcome definitions. Considering multiple outcomes can raise the general statistical issue of multiplicity: the more hypotheses tested, the greater the chance of at least one apparently notable result under a setting where none of the effects is real. Common approaches include defining a testing hierarchy or adjusting inference, but the registry record does not report a multiplicity strategy. No claim can be made about whether any adjustment was planned or used.
The primary endpoint uses a time window from baseline through Week 5 and can be met at any qualifying post-baseline visit. The record says the statistical analysis was performed for data up to Week 5 only. The analysis plan does not state whether repeated looks at the data or interim analyses were conducted; such details are not reported in the registry record.
For missing primary endpoint measurements, participants with no post-baseline hemoglobin values were classified as not achieving the threshold. When the Day 1 baseline value was missing, the screening or most recent pre-Day 1 value was used. The record does not describe other missing-data procedures, sensitivity analyses, or the extent of missing measurements.
The primary analysis population is described as randomized participants with any exposure to study drug, analyzed according to randomized assignment. This defines the stated population, but the record does not report the number of participants included in each primary endpoint analysis or how participants with other deviations were handled. Details of protocol deviations and additional analysis populations are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Ferumoxytol | 16 | 608 | 2.6% |
| Placebo | 6 | 200 | 3.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Ferumoxytol | 198 of 608 |
| Placebo | 56 of 200 |
Most frequent serious adverse event terms
| Event term | Organ system | Ferumoxytol | Placebo |
|---|---|---|---|
| Anaemia | Blood and lymphatic system disorders | 1 of 608 | 3 of 200 |
| Hypersensitivity | Immune system disorders | 3 of 608 | 0 of 200 |
| Supraventricular Tachycardia | Cardiac disorders | 1 of 608 | 0 of 200 |
| Colitis Ulcerative | Gastrointestinal disorders | 1 of 608 | 0 of 200 |
| Gastrointestinal Haemorrhage | Gastrointestinal disorders | 1 of 608 | 0 of 200 |
| Vomiting | Gastrointestinal disorders | 1 of 608 | 0 of 200 |
| Chest Pain | General disorders | 1 of 608 | 0 of 200 |
| Disease Progression | General disorders | 1 of 608 | 0 of 200 |
| Anaphylactic Reaction | Immune system disorders | 1 of 608 | 0 of 200 |
| Gastroenteritis | Infections and infestations | 1 of 608 | 0 of 200 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Ferumoxytol | Placebo |
|---|---|---|---|
| Headache | Nervous system disorders | 35 of 608 | 12 of 200 |
| Nausea | Gastrointestinal disorders | 28 of 608 | 5 of 200 |
| Dizziness | Nervous system disorders | 24 of 608 | 7 of 200 |
| Diarrhoea | Gastrointestinal disorders | 17 of 608 | 6 of 200 |
| Urinary Tract Infection | Infections and infestations | 17 of 608 | 6 of 200 |
| Nasopharyngitis | Infections and infestations | 16 of 608 | 4 of 200 |
| Abdominal Pain | Gastrointestinal disorders | 11 of 608 | 5 of 200 |
| Fatigue | General disorders | 12 of 608 | 3 of 200 |
| Vomiting | Gastrointestinal disorders | 12 of 608 | 2 of 200 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 9 of 608 | 5 of 200 |
Serious events with the highest arm-level rate: anaemia (1.5%), dysfunctional uterine bleeding (0.6%), lung neoplasm malignant (0.5%), convulsion (0.5%), hypersensitivity (0.5%).
The registry record lists serious adverse events for 16 of 608 participants at risk in the ferumoxytol group and 6 of 200 participants at risk in the placebo group. It lists other adverse events for 198 of 608 participants at risk in the ferumoxytol group and 56 of 200 participants at risk in the placebo group. These are recorded counts with the corresponding at-risk group sizes; they should not be confused with the primary hemoglobin endpoint.
The record also lists serious adverse event terms with percentages: Anaemia, 1.5%; Dysfunctional Uterine Bleeding, 0.6%; Lung Neoplasm Malignant, 0.5%; Convulsion, 0.5%; Hypersensitivity, 0.5%; and Supraventricular Tachycardia, 0.2%. Further detail about the denominator and event-level handling for these listed percentages is not reported in the registry record.
Adverse event counts describe events recorded during the trial; they do not, by themselves, establish that treatment caused an event. The record does not give a death count. The counts should be read as safety information reported by arm, separately from the efficacy outcome, and not as a complete characterization of risk.
12. What the Result Does, and Does Not, Mean
The trial record supports a clear description of the study question: a randomized, double-blind comparison of intravenous ferumoxytol and placebo for iron deficiency anemia, with a primary endpoint based on a hemoglobin increase of at least 2.0 g/dL through Week 5. It also describes the treatment schedules and the population intended for the primary analysis.
It does not, in the information available for this analysis, report the primary endpoint counts or a single treatment comparison. Consequently, the magnitude, direction, and precision of the primary result are not reported in the registry record. There is no basis in the stated information to conclude that the endpoint was more or less frequent in one group, or to quantify uncertainty around a difference.
The endpoint itself has a specific interpretation: it records whether the threshold was reached at any qualifying visit during a limited follow-up period. It does not summarize longer-term outcomes, the full trajectory of hemoglobin measurements, or every clinically relevant aspect of iron deficiency anemia. The secondary outcome definitions address other measures, but their definitions alone do not establish their results.
The adverse-event counts provide additional safety information, but event counts do not establish causality. The record does not report deaths, and further details about event timing, severity beyond the serious-event classification, or causal assessment are not included in the registry entries.
These limits distinguish what the registry record documents from what it does not. The design and endpoint can be described; a treatment-effect conclusion cannot be reconstructed from endpoint definitions alone. A reader should not interpret the absence of a reported primary comparison as evidence for either benefit or lack of benefit.
13. Why This Trial Matters Statistically
This trial is statistically notable as a randomized, double-blind, placebo-controlled, parallel-group Phase III study with a clearly defined short-term binary primary endpoint. The endpoint specifies a hemoglobin increase threshold and a fixed assessment window, allowing the study question to be framed in terms of the proportion of participants who met that criterion. The record also defines the baseline convention and how participants without post-baseline measurements were classified.
Those details matter because endpoint rules shape the result. A threshold-based endpoint is not equivalent to comparing average hemoglobin change: it distinguishes participants by whether they cross a specified cutoff, while an average change describes a group-level measurement. The registry record lists both kinds of outcome definitions among the trial outcomes, but does not report their numerical results in the registry record.
The record also illustrates why interpretation depends on more than design labels. Randomization and masking support a structured comparison, but the assessment of effect requires observed group results, an analysis method, and a measure of uncertainty. The primary counts and a single comparison are not reported in the registry record, so the design cannot substitute for missing outcome evidence.
Finally, the endpoint is limited to baseline through Week 5, and the safety information is reported separately. Keeping the time horizon, endpoint definition, and safety counts distinct helps prevent overinterpretation. The statistical significance strategy, missing-data sensitivity analyses, and broader analysis plan are not reported in the registry record.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most important limitation for statistical interpretation is that the registry record does not report the primary endpoint counts or a single comparison between treatment groups. Without those results, an effect estimate, confidence interval, or primary-endpoint p-value cannot be described. The record's endpoint definition and trial design alone do not reveal the observed result.
The primary endpoint is limited to whether a participant reached the specified hemoglobin increase at any time through Week 5. This binary definition does not preserve the full size or timing of changes, and the short assessment window does not describe outcomes after Week 5. The record states that participants with no post-baseline hemoglobin values were classified as not achieving the endpoint, but the extent of missing post-baseline data is not reported.
The registry record does not report the randomization method, allocation concealment, the full masking procedures, or the statistical analysis plan. Multiplicity handling, interim analyses, sensitivity analyses, and the primary sample-size justification are not reported in the registry record. The sample-size assumptions described are for a planning illustration, not evidence of observed power or the trial's original design rationale.
The safety information includes event counts and selected serious-event terms, but does not give a death count or all details needed to interpret the listed percentages. Adverse event counts alone do not establish causality. These limits constrain what can be concluded from the record without changing the study design or endpoint definitions that it does report.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Trial Comparing Ferumoxytol With Placebo for the Treatment of Iron Deficiency Anemia — NCT01114139.
- Registry record last updated 2022-04-21; status last verified 2022-03.
- Results first posted 2018-06-11.
- 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 NCT01114139, a completed Phase III randomized, double-blind, placebo-controlled parallel-group trial of ferumoxytol for iron deficiency anemia. Enrollment is listed as 812. The active-treatment arm received two intravenous 510 milligram doses, and the placebo arm received two intravenous saline doses.
The primary endpoint counted participants achieving a hemoglobin increase of at least 2.0 g/dL from baseline through Week 5. The primary analysis population was defined as randomized participants with any exposure to study drug, analyzed by randomized assignment. The record lists five secondary outcomes and safety-event counts by arm.
The primary outcome counts and a single treatment comparison are not reported in the registry record. The statistical analysis plan, multiplicity strategy, and primary sample-size justification are also not reported in the registry record.