An Observational Study of Methoxy Polyethylene Glycol-epoetin Beta in Participants With a Kidney Transplant: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Observational Study of Methoxy Polyethylene Glycol-epoetin Beta in Participants With a Kidney Transplant (NCT02538107), a registered phase not stated study. The primary outcome is Percentage of Participants With a Hemoglobin Value of 11-12 Grams Per Deciliter (g/dL) From Visit 7 (Month 7) to Visit 9 (Month 9).

2. Clinical Question

The study describes data collection during 15 months of Mircera therapy among people with a kidney transplant. The primary outcome focuses on the proportion meeting the stated hemoglobin range during the period from Visit 7 to Visit 9. This is a descriptive question about the observed participants and their hemoglobin values during follow-up, not a randomized comparison of treatment against a control.

The registry record also lists secondary outcomes relating hemoglobin levels to the type of kidney transplantation, inflammatory diseases, chronic kidney disease etiology, acute bleeding episodes during the study, and glomerular filtration rate. These outcomes suggest that the record was intended to characterize hemoglobin in relation to clinical features. Their individual results are not reported in the registry record.

The registry record describes 290 enrolled participants, but the primary outcome population is narrower: it includes participants who reported no pregnancy during the study period and had dosing and hemoglobin data available during at least one of Visits 7–9. The number meeting those criteria is not reported in the registry record. Without a reported outcome estimate or a comparator, the record does not establish a treatment effect. It identifies the population, treatment exposure, follow-up period, and hemoglobin outcome of interest.

3. Trial Design

This was a completed, non-interventional observational study sponsored by Hoffmann-La Roche. Its title and description identify methoxy polyethylene glycol-epoetin beta, also called Mircera, as the treatment being observed in participants with a kidney transplant. The participants were receiving the drug as part of their medical care; the registry record does not describe assignment by the study to treatment or a control condition. Allocation is not stated, and no like-for-like control comparison is described.

The record gives an enrollment of 290. It describes data collection over 15 months of Mircera therapy. The study start date is 2007-09-30, and the primary completion date is 2011-11-30. The status is COMPLETED. These dates describe the registry record and do not supply additional information about how individual participants entered or completed follow-up.

The primary outcome is the percentage of participants with a hemoglobin value of 11–12 g/dL from Visit 7 (Month 7) to Visit 9 (Month 9). Its analysis population is described as participants who reported no pregnancy during the study period and had dosing and hemoglobin data available during one of the three visits spanning Visits 7–9. The size of that analysis population and the observed percentage are not reported in the registry record.

The record lists 12 outcome measures, including secondary outcomes concerning hemoglobin by transplantation type, inflammatory disease, chronic kidney disease etiology, acute bleeding episodes, and glomerular filtration rate. It lists no statistical analyses. Details such as the schedule of all measurements, any planned comparison, prespecified adjustment variables, and the statistical plan are not reported in the registry record. Because this is observational, treatment exposure reflects routine medical care as described in the record, rather than a randomized assignment that would create directly comparable groups.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Efficacy analysis set (Included participants who reported no pregnancy during the study period and had dosing and hemoglobin data available during 1 of the 3 visits \[Visits 7-9\]).

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: Safety analysis set included participants who received at least 1 dose of study treatment. Age was reported for N=278 participants since data for 1 participant was missing.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With a Hemoglobin Value of 11-12 Grams Per Deciliter (g/dL) From Visit 7 (Month 7) to Visit 9 (Month 9), measured over From Month 7 to Month 9.

The primary endpoint is the percentage of participants with a hemoglobin value of 11–12 g/dL from Visit 7 (Month 7) to Visit 9 (Month 9). It is a binary, participant-level outcome: each person either meets the stated range during the specified visits or does not, according to the endpoint definition. The registry record describes the measure as a percentage of participants and gives its timeframe as Month 7 to Month 9.

A proportion can summarize how common a defined outcome was in the eligible analysis population. In this study, it gives a way to describe how many participants met the stated hemoglobin range during the specified follow-up period. It does not, by itself, describe the amount of change in hemoglobin for each participant, nor does it establish why a value fell within or outside that range. The underlying measurement rules for assigning participants to the endpoint are not reported in the registry record.

The endpoint is framed as a target range rather than as a comparison between treatment groups. Interpretation therefore depends on the number of participants eligible for the analysis, the observed proportion, and the precision of that estimate. Those outcome results are not reported in the registry record. The defined analysis population excludes participants who reported pregnancy during the study period and requires dosing and hemoglobin data during at least one of Visits 7–9. The number excluded or missing data are not reported in the registry record.

As a general statistical point, a proportion is most informative when its denominator and the rules for outcome classification are clear. The registry record identifies the intended population and timeframe, but does not report the numerical endpoint result or its uncertainty.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a percentage, which is a summary of the number of participants meeting a defined condition relative to the eligible analysis population. In this study, the condition is having a hemoglobin value of 11–12 g/dL from Month 7 to Month 9. The endpoint is therefore a binary outcome at the participant level, as opposed to a continuous summary of each participant’s hemoglobin measurements. The observed percentage and its denominator are not reported in the registry record.

What does a confidence interval tell a reader?

In general, a confidence interval describes statistical uncertainty around an estimate. For a proportion, it indicates a range of values compatible with the observed data under the assumptions of the interval method. A narrow interval indicates greater precision than a wide interval, while neither interval alone resolves possible bias in who was included or how measurements were obtained. No confidence interval for the primary outcome is reported in the registry record, so its precision cannot be assessed from the posted results.

What does an observational design imply?

In general, an observational study records exposures and outcomes as they occur in medical care rather than assigning participants at random. This can describe experience in the studied group, but it does not create the balance between treatment groups that randomization is intended to achieve. Differences in participant characteristics, clinical care, or reasons for treatment may influence outcomes. Here, the record describes participants receiving Mircera as part of their medical care and does not describe a comparison group. It does not report methods for adjusting for differences or other potential influences.

How should the analysis population be understood?

The primary analysis set is restricted to participants who reported no pregnancy during the study period and had dosing and hemoglobin data available during at least one of Visits 7–9. Such eligibility rules determine which participants contribute to the primary endpoint. In general, an analysis restricted to participants with available measurements can differ from the full enrolled group if data availability is related to health status, treatment, or outcomes. The size of the analysis set, the reasons for unavailable measurements, and any assessment of the consequences of exclusions are not reported in the registry record.

What are planning calculations for?

In general, sample-size calculations describe how many participants might be needed under specified assumptions to detect an effect of a chosen size with a chosen statistical approach. They are planning illustrations, not observed power and not evidence that a study detected an effect. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Those assumptions do not describe the observational study design, which has no like-for-like control comparison in the registry record. The illustration is based on an observed effect, but the primary outcome effect is not reported in the registry record. It should not be read as the study’s own sample-size justification, which is not reported in the registry record.

Why does over-dispersion matter in general?

Over-dispersion occurs when variation in observed data is greater than a statistical model expects. In general, ignoring excess variation can make uncertainty appear smaller than it is, leading to confidence intervals or tests that are too optimistic. Whether over-dispersion is relevant depends on the outcome and model. The registry record does not report a model or analysis that would allow readers to assess this issue for the primary endpoint.

What can be inferred from the registry's analysis listing?

The record lists no statistical analyses. This means the posted information does not specify a fitted model, inferential procedure, covariate adjustment, or method for obtaining uncertainty estimates. General statistical interpretation of a proportion remains possible, but attributing any particular method to this study would go beyond what the registry record reports. The endpoint definition, analysis population, and timeframe are stated; the details of the analysis and the numerical primary result are not.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Kidney Transplant Participants")
n      <- c(193)
events <- c(40)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Kidney Transplant Participants  193  40  20.7  15.2  27.1  15.6  27.0  15.6  27.0

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 12 outcome measures, including the primary hemoglobin measure and secondary hemoglobin outcomes relating to clinical characteristics and events. When a study examines multiple outcomes, general statistical practice considers how repeated testing affects the chance of finding an apparently notable result by chance. A prespecified approach to multiplicity may address that issue. Any such approach, including whether adjustments were planned or used, is not reported in the registry record. No statistical analyses are listed.

The primary analysis population requires no reported pregnancy during the study period and dosing and hemoglobin data during at least one of Visits 7–9. The record does not report how many enrolled participants met these criteria, how many measurements were missing, or why measurements may have been unavailable. It does not report an imputation method, a sensitivity analysis, or another method for handling missing data. As a general matter, missingness can affect a proportion if the availability of measurements is related to whether participants meet the endpoint.

The registry record does not report whether analyses followed a prespecified protocol, how any departures were handled, or whether participants were excluded for reasons beyond the stated analysis-set criteria. The number of statistical analyses listed is zero. Consequently, it is not possible to evaluate multiplicity control, missing-data assumptions, or the consistency between planned and reported analyses from the registry record. The reported endpoint definition establishes the question of interest, but not the inferential procedures used to answer it.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (1.8%), blood creatinine increased (1.4%), urinary tract infection (1.1%), diarrhoea (0.7%), gastroenteritis (0.7%).

For the kidney transplant participant group, the safety listing gives 279 participants at risk, 32 affected by serious adverse events, and 42 affected by other adverse events. These are participant counts as listed in the registry record. The record does not describe a comparison group, so the counts cannot be interpreted as a comparative estimate of safety. The record also does not establish that an adverse event was caused by methoxy polyethylene glycol-epoetin beta.

The listed serious adverse event terms and percentages are pneumonia, 1.8%; blood creatinine increased, 1.4%; urinary tract infection, 1.1%; diarrhoea, 0.7%; gastroenteritis, 0.7%; and haemoglobin decreased, 0.7%. These are the terms and percentages appearing in the registry record. They should be read as reported event listings, not as a ranking of treatment effects or evidence of causation. The record does not give further detail about event timing, severity beyond the serious classification, or whether participants experienced more than one event.

Deaths are not reported in the registry record. The figures describe safety events recorded in the study group; without a control comparison and additional context, they do not quantify excess risk attributable to treatment.

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

The study addresses the observed hemoglobin status of kidney transplant participants receiving methoxy polyethylene glycol-epoetin beta as part of their medical care. Its primary outcome asks what percentage had a hemoglobin value of 11–12 g/dL from Month 7 to Month 9. The registry record defines the analysis population and the outcome timeframe, but does not report the observed percentage. It also does not report a confidence interval or other measure of uncertainty for that endpoint.

Accordingly, the posted information does not show how often participants met the specified range, how precisely that frequency was estimated, or how results varied across participants. It does not report the primary outcome result for all enrolled participants or the number included in the efficacy analysis set. The listed secondary outcome topics do not supply results for those analyses.

The observational design is important to what the study can establish. The participants received the treatment as part of their medical care, and no like-for-like control comparison is described. A descriptive outcome in this group would not, on its own, show what would have happened to the same participants without treatment or distinguish treatment-related changes from other factors. The record does not describe methods intended to address confounding.

The safety listing provides counts of participants affected by serious and other adverse events and percentages for listed serious adverse event terms. Those descriptions are not equivalent to a comparison of treatment-associated risk, and the record does not establish causality. Deaths are not reported in the registry record.

In general, a study can be informative about the outcome it set out to describe while still leaving important questions unanswered. Here, the endpoint and intended population are stated, but the numerical primary result, statistical precision, analysis methods, missing-data handling, and comparator information are not reported in the registry record. The record therefore supports understanding of the study question and design, not a quantitative conclusion about treatment effect or comparative safety.

14. Why This Trial Matters Statistically

This study is statistically notable for the distinction between describing an outcome during routine medical care and estimating a causal treatment effect. The participants were receiving methoxy polyethylene glycol-epoetin beta as part of their medical care, and the registry record does not describe a control group or random allocation. This makes the intended primary question a description of the proportion meeting a hemoglobin range, rather than a randomized comparison.

The endpoint also illustrates why a clear denominator matters. The primary outcome applies to participants without reported pregnancy during the study period who had dosing and hemoglobin data available during at least one of Visits 7–9. That definition is more specific than the overall enrollment of 290. The size of the eligible analysis group and the outcome proportion are not reported in the registry record, limiting both interpretation and assessment of precision.

The registry lists 12 outcome measures but no statistical analyses. This leaves important methodological questions unanswered, including how multiple outcomes were handled, how missing measurements were addressed, and whether any adjustment for differences among participants was used. These omissions matter because methods and exclusions can shape the meaning of an observed proportion.

The safety information offers descriptive participant counts and event terms, but no comparative estimate. This is a useful distinction in reading observational records: counts can document events in a studied group without showing whether treatment caused them or whether their frequency differs from another care approach. The record's missing primary result further means that the central efficacy question cannot be answered quantitatively from the posted information.

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.

The main limitation for interpretation is that the registry record does not report the primary endpoint result. The number or percentage of participants with hemoglobin values of 11–12 g/dL from Month 7 to Month 9, together with any measure of statistical precision, is not reported in the registry record. The eligible efficacy analysis population size is also not reported.

The study is observational, and the record describes participants receiving Mircera as part of their medical care. No comparison group is described, and allocation is not stated. Therefore, the design information does not support a direct treatment-versus-control contrast. The record does not report adjustment methods that might address differences among participants or other factors associated with receiving treatment and hemoglobin outcomes.

The registry record lists 12 outcome measures but no statistical analyses. It does not report an analysis plan, model, hypothesis-testing procedure, multiplicity approach, or missing-data method. The reasons for unavailable dosing or hemoglobin data, the number of participants excluded from the efficacy analysis set, and the effect of any exclusions are not reported in the registry record.

The safety listing gives participant counts and percentages for serious adverse event terms, but the record does not provide a comparative safety analysis or establish that events were caused by treatment. Deaths are not reported in the registry record. The record also does not report further information on event timing or recurrence. These limitations leave the posted information useful for identifying the study population, exposure, outcome definitions, and recorded safety categories, but insufficient for estimating treatment effects or assessing the precision of the primary outcome.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: An Observational Study of Methoxy Polyethylene Glycol-epoetin Beta in Participants With a Kidney Transplant — NCT02538107.
• Registry record last updated 2017-06-07; status last verified 2017-05.
• Results first posted 2015-11-03.
• 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

The registry record describes a completed, non-interventional observational study of methoxy polyethylene glycol-epoetin beta in participants with a kidney transplant and chronic kidney disease. The sponsor is Hoffmann-La Roche. Enrollment was 290, and the record describes data collection over 15 months of Mircera therapy. The study started on 2007-09-30, with primary completion on 2011-11-30.

The primary outcome was the percentage of participants with a hemoglobin value of 11–12 g/dL from Visit 7 (Month 7) to Visit 9 (Month 9). The analysis set excluded participants who reported pregnancy during the study period and required dosing and hemoglobin data during at least one of Visits 7–9. The primary outcome result and analysis population size are not reported in the registry record. The record lists 12 outcome measures and no statistical analyses.

Safety information lists 279 participants at risk, 32 affected by serious adverse events, and 42 affected by other adverse events. Deaths are not reported in the registry record. No like-for-like control comparison is described.