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 Study Evaluating BeneFIX in Patients With Haemophilia B, Previously Treated With Plasma Derived Factor IX (NCT00749476), a non-randomized phase 4 study. The primary outcome is Number of Participants Reporting Efficacy.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00749476 |
| Phase | Phase 4 |
| Condition | Hemophilia B |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 1 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Wyeth is now a wholly owned subsidiary of Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients with haemophilia B who had previously received plasma-derived Factor IX (pdFIX). The registry records enrollment of 1 participant. The primary outcome description identifies the Intent to Treat (ITT) population and notes that the small number of participants who completed the study prevented descriptive statistics for the efficacy endpoints.
Intervention
The study assessed the conversion to BeneFIX, a Factor IX product. The registry describes the intervention as Factor IX recovery and says that biological efficacy, meaning recovery with BeneFIX, was measured just after conversion. The study also collected clinical efficacy information around the transition.
Comparator
This was a single-group, non-randomized study with no masking. It was not a randomized comparison, and the registry does not describe a like-for-like control group. The collection of information about pdFIX before conversion and BeneFIX after conversion does not make the study a randomized comparison between treatment arms.
Primary question
The primary outcome was the number of participants reporting efficacy over a registry timeframe of 4 months. The assessment covered bleeding episodes and their location, injections per bleeding, Factor IX consumption, investigator and patient global assessments of efficacy, and biological recovery with BeneFIX just after conversion. The registry record does not provide descriptive statistics for these efficacy endpoints.
The study’s stated purpose was to collect information around conversion from pdFIX to BeneFIX. Its summary describes a retrospective history of bleeding in the 3-month period before conversion, recovery with pdFIX just before conversion, recovery with BeneFIX just after conversion, and a prospective history of bleeding in the 3 month period following conversion. These are the intended observation periods and assessments described in the record; they do not establish that numerical results were reported for each measure.
The central statistical question is therefore descriptive: what efficacy and recovery information was collected around the transition, and what can the registry report establish about it? With no descriptive efficacy statistics recorded, the registry cannot quantify the observed efficacy outcome or its precision.
3. Trial Design
The record describes a completed phase 4 study with a single-group model, non-randomized allocation, and no masking. Enrollment was 1. The study title and summary identify the focus as conversion from plasma-derived Factor IX to BeneFIX in patients with haemophilia B previously treated with pdFIX. The recorded intervention is Factor IX recovery. The sponsor entry says Wyeth is now a wholly owned subsidiary of Pfizer.
The study began in 2008-04, and the primary completion date is 2009-01. Its status is completed. The registry’s description emphasizes collecting information around the conversion rather than assigning participants randomly to competing treatment groups. It describes past bleeding history before conversion and prospective bleeding history following conversion, along with recovery assessments immediately around the transition.
Because the study is single-group and non-randomized, it does not provide a randomized treatment contrast. Measurements before and after conversion may describe observations at different points in a participant’s course, but they are not equivalent to outcomes from randomized, concurrent treatment groups. The record also does not report masking, consistent with its designation of no masking.
The registry identifies one primary outcome measure and zero analyses. The endpoint is titled Number of Participants Reporting Efficacy, with participants as the unit and a timeframe of 4 months. The outcome description lists several kinds of clinical assessment and a biological recovery assessment. The registry states that descriptive statistics for efficacy endpoints were not provided because a low number of subjects completed the study.
The record does not report a detailed protocol, recruitment procedures, eligibility criteria beyond the previously treated population described in the title, or the reasons for the study’s enrollment and completion numbers. Those details should not be inferred from the study design labels. The design supports a limited descriptive account of the conversion period; the posted results do not support an estimate of a comparative treatment effect.
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: Before enrollment there was up to a 14 day screening period and the investigator reviewed the subject's medical history and medications to ensure that the subject was in good health and met all of the inclusion criteria and none of the exclusion criteria.
Overall Study
| Stage | BeneFIX |
|---|---|
| STARTED | 1 |
| COMPLETED | 1 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Intent to Treat (ITT) population. Due to low number of subjects that completed, no descriptive statistics for the efficacy endpoints are provided.
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 | BeneFIX |
|---|---|---|
| Participants analysed | 1 | |
| Age Continuous | years | 27.0 (SD 0.0) |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Reporting Efficacy, measured over 4 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is titled Number of Participants Reporting Efficacy. Its unit is participants, its parameter is a number, and its registry timeframe is 4 months. The endpoint description defines efficacy broadly: clinical efficacy was assessed through the number and location of bleeding episodes, injections per bleeding, Factor IX consumption, and global assessments by the investigator and patient. Biological efficacy was assessed through recovery with BeneFIX just after conversion.
A participant count can provide a straightforward summary of how many people meet a prespecified reporting definition. In general, endpoint definitions matter because they determine which observations count as an event or response and what period is covered. A broad endpoint description such as this one includes several distinct clinical and biological measures; the registry record does not provide a combined definition explaining how those measures determine whether a participant is counted as reporting efficacy.
The endpoint is useful for organizing the study’s intended assessment of the conversion period, but interpretation depends on having the underlying definitions, results, and denominators. The record says that descriptive statistics for efficacy endpoints were not provided because few subjects completed the study. It therefore does not give the number of participants reporting efficacy or detail the results for the endpoint’s component measures. Without those results, the endpoint’s observed value and precision cannot be assessed from the registry.
The registry timeframe of 4 months is stated alongside a study summary describing bleeding histories in the 3-month periods before and after conversion and recovery measurements around conversion. These descriptions should be reported as written; the record does not explain how the endpoint timeframe relates to each component assessment.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The most important interpretive feature is the absence of descriptive statistics for the primary efficacy endpoints. The registry explicitly attributes this to the low number of subjects who completed the study. Although enrollment is recorded as 1, the registry does not provide an efficacy count, a measure of uncertainty, or a detailed account of completed-participant outcomes. The intended assessments are described, but their numerical results cannot be reconstructed from those descriptions.
The design also limits what kinds of conclusions the study could support. It is a single-group, non-randomized study with no masking, and the record does not identify a randomized control group. The pre-conversion pdFIX history and post-conversion BeneFIX history are parts of the study’s observation plan, not a randomized comparison. Changes between observation periods could not, on the basis of this record alone, be attributed to the product transition while excluding other explanations.
The primary outcome is a participant count, but the registry does not state the observed count. The endpoint description includes bleeding episodes, their location, injections per bleeding, Factor IX consumption, global efficacy assessments, and recovery. These measures address different aspects of the study question. Without component results and definitions for how they relate to the participant-level endpoint, readers cannot determine which measure contributed to any overall efficacy classification.
The registry reports a serious adverse event term, Herpes simplex type-2 (HSV-2) meningitis, at 100.0%. It also records 1 participant at risk and 1 affected for serious adverse events in the BeneFIX group. These safety entries describe the posted adverse-event reporting; they do not supply an efficacy result or a comparative estimate. The record’s death value is not reported in the registry record.
Precision is not assessable for the efficacy endpoint because no numerical result or confidence interval is reported. In general, a confidence interval describes the uncertainty around an estimate; it cannot be interpreted when the underlying estimate and interval are absent. Small amounts of information can make estimates unstable, but the registry does not provide enough efficacy data to characterize that uncertainty quantitatively.
The record should therefore be read as documenting a study purpose, design, planned assessments, and limited safety reporting, rather than as providing a numerical efficacy analysis. The completed status does not itself establish that every planned assessment has a posted result. The registry’s stated reason for not presenting descriptive efficacy statistics is the low number of subjects who completed the study.
9. Statistical Methods Explained
The study is classified as single-group and non-randomized, with no masking. In general, random allocation helps make treatment groups comparable at the start of a trial, while masking can reduce the influence of knowledge about treatment assignment on assessment. Neither feature is part of the design described in this record. There is no like-for-like randomized control comparison identified, so the study does not estimate a randomized between-group effect.
The record describes collection before and after conversion. In general, a before-and-after assessment follows observations across time rather than comparing concurrently randomized groups. Such a design can document the course of measured outcomes, but time-related changes and other influences can complicate interpretation. The registry does not describe an analysis that adjusts for such influences, and no adjustment procedure should be assumed.
How should the endpoint be understood?
The primary outcome is a participant count for those reporting efficacy, over a timeframe of 4 months. In general, a count endpoint requires a clear rule for deciding which participants qualify. The endpoint description names bleeding measures, investigator and patient global assessments, Factor IX consumption, and post-conversion recovery, but the record does not provide a detailed operational rule that combines these components into the participant count.
Counts are not interchangeable with rates or time-to-event measures. A count describes how many participants meet a defined condition; a rate would also account for exposure time, and a time-to-event analysis would focus on the time until an event. The registry identifies the primary parameter as a number of participants, not a rate or time-to-event outcome. It does not provide an efficacy count or additional details sufficient to calculate another measure.
What can be said about the analyses?
The registry records zero analyses. It also states that descriptive statistics for efficacy endpoints were not provided because a low number of subjects completed the study. There are consequently no posted estimates of the primary efficacy outcome, no confidence intervals, and no reported hypothesis tests for that outcome in the record. The absence of these statistics is not evidence of a particular efficacy result.
A confidence interval, in general, expresses the range of values compatible with an estimate under the assumptions of the statistical method. Its width conveys precision: a wider interval indicates less precision than a narrower one. No confidence interval is reported for the efficacy endpoint, so its precision cannot be evaluated numerically. A p-value, in general, measures how unusual data would be under a specified null hypothesis and model. No efficacy p-value or corresponding hypothesis test is reported.
What do the sample-size planning assumptions mean?
The registry describes a sample-size planning illustration based on an observed effect, not the trial’s own design. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the intended effect is a stated fraction of the observed effect. For time-to-event illustrations, the stated quantity is the total number of events using the Schoenfeld method; other illustrations use participants per arm.
These are planning assumptions, not evidence that the study used those design features. In particular, equal allocation between two arms does not match the recorded single-group design. The record does not give a numerical observed effect or a sample-size justification for the actual study. Any planning illustration based on an effect is therefore distinct from an observed trial result. Sample-size calculations are prospective planning tools and must not be interpreted as observed power. No power result for this study is reported.
In general, over-dispersion occurs when variability in count data exceeds what a simple model assumes. It can affect uncertainty estimates and the suitability of a model. The registry does not report a count-model analysis or an assessment of over-dispersion for the efficacy outcomes, so no such method or finding can be attributed to this study.
How should missing numerical results be handled?
When results are not reported, readers should not infer values from the study purpose, status, or adverse-event entries. The efficacy outcome remains unquantified in the registry record. Recalculation from summary statistics is not possible because the efficacy summaries needed for a recalculation are not reported. The posted information supports a description of design and intended measurement, but not a numerical reconstruction of the primary efficacy result.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies one primary outcome measure and zero analyses. It does not report a statistical analysis plan, a multiplicity adjustment, or a strategy for controlling error across multiple endpoints or comparisons. The endpoint itself includes several clinical measures and a biological recovery assessment, but the registry does not explain whether these were analyzed separately, combined into a rule, or treated in another way.
In general, multiplicity arises when multiple hypotheses or endpoints are assessed. Without a stated analysis plan, readers cannot determine which outcomes were intended to be confirmatory, how any testing hierarchy was defined, or whether an adjustment was planned. No multiplicity procedure should be presumed for this study.
The endpoint description identifies the ITT population. It also states that descriptive statistics for efficacy endpoints were not provided because a low number of subjects completed the study. The record does not report how participants were classified for the ITT population, how post-conversion observations were handled, or whether any participants were excluded from particular analyses.
Missing-data methods are not reported in the registry record. There is no description of imputation, handling of incomplete follow-up, or sensitivity analysis for missing outcomes. The registry gives an enrollment of 1, but does not provide a detailed participant flow or explain the completion status of individual participants. These gaps prevent assessment of whether missing observations could have affected the efficacy results.
In general, missing-data methods depend on why observations are unavailable and on the assumptions used to address them. Because neither the pattern nor the handling of missing data is described, no assumptions about missing outcomes can be verified. The reported absence of descriptive statistics should not be replaced with an imputed result or an inferred analysis.
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 |
|---|---|---|---|
| BeneFIX | 1 | 1 | 100.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| BeneFIX | 1 of 1 |
Most frequent serious adverse event terms
| Event term | Organ system | BeneFIX |
|---|---|---|
| Herpes simplex type-2 (HSV-2) meningitis | Infections and infestations | 1 of 1 |
Most frequent non-serious adverse event terms
| Event term | Organ system | BeneFIX |
|---|---|---|
| Allergic rhinitis | Respiratory, thoracic and mediastinal disorders | 1 of 1 |
| Diarrhea | Gastrointestinal disorders | 1 of 1 |
| Acute renal failure | Renal and urinary disorders | 1 of 1 |
| Lower back pain | Musculoskeletal and connective tissue disorders | 1 of 1 |
Serious events with the highest arm-level rate: herpes simplex type-2 (hsv-2) meningitis (100.0%).
The BeneFIX group has 1 participant recorded as at risk and 1 affected for serious adverse events. The listed serious adverse event term is Herpes simplex type-2 (HSV-2) meningitis, reported at 100.0%. The registry also records 1 participant at risk and 1 affected for other adverse events. These are the posted safety counts and term, and they should be read in the context of the small recorded group.
In general, an at-risk count describes the denominator used for an adverse-event summary, while an affected count describes participants reported with an event. A percentage is meaningful only alongside its denominator and the way events were classified. The registry’s 100.0% entry is a reported proportion for the listed term; it does not provide a stable estimate of how often the event would occur in a broader population. With the recorded group size, the entry is a description of this study record, not a comparative safety estimate.
The record does not identify a randomized control group, so these counts cannot be used to estimate a difference in serious adverse events between treatment groups. Deaths are not reported in the registry record. The registry does not provide additional details about event timing, duration, management, or causal assessment in the registry record reported for this study. Those details should not be inferred from the event term or percentage.
12. What the Result Does, and Does Not, Mean
The record establishes that a completed phase 4, single-group study was conducted to collect information around conversion from pdFIX to BeneFIX in patients with haemophilia B. It describes the intended clinical and biological assessments, including bleeding history around conversion and Factor IX recovery measurements. It also reports limited adverse-event information for the BeneFIX group.
The record does not establish a numerical efficacy result. The primary endpoint is named and described, but descriptive statistics were not provided because a low number of subjects completed the study. The registry does not report the number of participants meeting the efficacy endpoint, the results for the endpoint’s individual components, or uncertainty estimates for those outcomes. A completed status does not fill in these missing results.
The study also does not provide a randomized comparison of BeneFIX with pdFIX. The fact that the record describes pdFIX assessments before conversion and BeneFIX assessments after conversion does not by itself establish a controlled treatment effect. In general, comparison across periods can be affected by the passage of time and other factors, and the record does not report an analysis addressing those issues.
The serious adverse-event entry describes what was reported in the study group, including Herpes simplex type-2 (HSV-2) meningitis at 100.0%. It should not be interpreted as a comparative risk estimate or generalized from this record alone. The available entry does not supply a broader estimate of event frequency.
Statistically, the study is best understood as a limited descriptive investigation with incomplete numerical efficacy reporting in the registry. It can document the purpose, design, and reported safety information, but it cannot establish the magnitude or precision of an efficacy outcome. It also cannot support a treatment comparison that the design did not make.
13. Why This Trial Matters Statistically
This study is statistically informative because it illustrates the distinction between a study’s intended measurements and results that can actually be interpreted. The registry lays out a focused transition question, with retrospective bleeding history before conversion, prospective bleeding history after conversion, and recovery assessments around conversion. Yet it states that descriptive efficacy statistics were not provided because few subjects completed the study. A well-described measurement plan does not substitute for reported outcome data.
The design labels also matter. A single-group, non-randomized study can organize observations around a treatment transition, but it does not create a randomized comparison. Readers need to distinguish a before-and-after observation plan from a controlled estimate of treatment effect. This distinction is important when interpreting any endpoint that spans time around a conversion.
The record also shows why denominators are essential for safety interpretation. It reports a serious adverse event term at 100.0% alongside 1 participant at risk and 1 affected in the group. The percentage must be read as a description of the recorded group, rather than as a general estimate. It is not a comparison with an alternative treatment.
Finally, the stated sample-size planning framework should not be confused with the trial’s actual design or with evidence of observed power. Planning assumptions about two arms and an effect to detect are methodological illustrations, whereas this study is recorded as single-group and no numerical efficacy effect is reported. Keeping design, planning, and observed results separate prevents unsupported conclusions from being drawn from sparse registry information.
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 principal limitation is that the registry does not provide descriptive statistics for the efficacy endpoints. It explicitly links this omission to the low number of subjects who completed the study. Enrollment is recorded as 1, but a detailed account of participant completion and the availability of each outcome is not reported in the registry record.
The primary endpoint covers multiple clinical and biological measures, but the registry does not report detailed scoring rules or explain how they relate to the participant-level efficacy count. The registry timeframe is 4 months, while the study summary describes bleeding histories during 3-month periods before and after conversion and recovery measurements immediately around conversion. The record does not explain the relationship among these stated timeframes.
The design is single-group, non-randomized, and unmasked. No like-for-like randomized control comparison is reported. Consequently, the record cannot provide a randomized estimate comparing BeneFIX with pdFIX, and any interpretation of observations across the conversion must remain descriptive.
The registry records zero analyses and does not report an analysis plan, hypothesis tests, confidence intervals, multiplicity handling, or missing-data methods. It does not provide enough numerical efficacy summaries for independent recalculation. The stated planning assumptions do not supply an observed effect or a justification for the actual enrollment.
Safety reporting is also limited in the record described. The serious event term and group counts are reported, but event timing, duration, and further clinical details are not. Deaths are not reported in the registry record. These limitations constrain interpretation to the information actually recorded.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study Evaluating BeneFIX in Patients With Haemophilia B, Previously Treated With Plasma Derived Factor IX — NCT00749476.
- Registry record last updated 2011-06-08; status last verified 2011-06.
- Results first posted 2010-06-29.
- 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
This completed phase 4 study, NCT00749476, concerned conversion from plasma-derived Factor IX to BeneFIX in patients with haemophilia B previously treated with pdFIX. It was single-group, non-randomized, and unmasked, with enrollment of 1. The record describes bleeding histories around conversion and recovery assessments with pdFIX and BeneFIX. The primary endpoint was the number of participants reporting efficacy over a timeframe of 4 months.
The registry states that descriptive statistics for efficacy endpoints were not provided because a low number of subjects completed the study. It records zero analyses. The BeneFIX group safety entry lists 1 participant at risk and 1 affected for serious adverse events, with Herpes simplex type-2 (HSV-2) meningitis reported at 100.0%. Deaths are not reported in the registry record. The available information supports a description of study design, intended assessments, and limited safety reporting, but not a numerical efficacy estimate or randomized treatment comparison.