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 Pilot Study of KRX-0502 (Ferric Citrate, Administered Without Food, in Treating Iron-deficiency Anemia (NCT02128074), a na phase 2 study. The primary outcome is Change in Hemoglobin From Baseline to the End of 8-week Treatment Period.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02128074 |
| Phase | Phase 2 |
| Condition | Anemia of Chronic Kidney Disease |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 32 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Keryx Biopharmaceuticals |
| Results posted | Yes |
2. Clinical Question
Population
People with iron-deficiency anemia and stage 3-5 non-dialysis dependent chronic kidney disease were the intended study population. The registry lists anemia of chronic kidney disease as a condition and describes the population as patients with NDD-CKD. Further eligibility details are not reported in the registry record.
Intervention
The study evaluated KRX-0502, identified as ferric citrate, administered without food. The registry describes an 8-week treatment period. Details of the dose, schedule, adherence, and any treatment changes are not reported in the registry record.
Comparator
There was no separate comparator group. The design is recorded as single group, with allocation listed as NA and masking listed as none. Thus, the study does not provide a randomized, like-for-like comparison against placebo or another treatment.
Primary question
The primary outcome was the mean change in hemoglobin from baseline to the end of the 8-week treatment period, measured in g/dL. The registry record does not report the numerical mean change, its standard deviation, or an inferential result. The study therefore identifies the question it set out to examine, but the posted record does not quantify the observed change.
3. Trial Design
This was a Phase 2 pilot study recorded as completed. It evaluated KRX-0502, described as ferric citrate, administered without food to patients with stage 3-5 non-dialysis dependent chronic kidney disease and iron-deficiency anemia. The registry lists Keryx Biopharmaceuticals as the sponsor. The study began in 2014-04, and primary completion is recorded as 2014-11.
The design is classified as single group, with allocation listed as NA and masking listed as none. Those details indicate that this record does not describe random assignment or a blinded comparison. There is no separate control arm against which to estimate a treatment-group contrast. The enrolled number is 32, but the registry record does not report how many participants contributed data to the primary outcome or whether all enrolled participants completed the treatment period.
The primary outcome was change in hemoglobin from baseline to the end of the 8-week treatment period. The record identifies the outcome as a mean of a continuous measure, with standard deviation as the stated dispersion. It does not provide the numerical mean, standard deviation, confidence interval, or statistical test result. No analysis is listed in the record. Details of the protocol, treatment schedule, follow-up beyond the stated period, and analysis populations are not reported in the registry record.
The pilot designation and single-group structure matter when interpreting the study. A before-and-after change within a treated group can describe the observed course during the study, but without a concurrent comparator it cannot isolate the change attributable to treatment from other influences. The registry record does not report a sample-size justification or the protocol’s statistical plan.
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 | KRX-0502 |
|---|---|
| STARTED | 32 |
| COMPLETED | 26 |
| NOT COMPLETED | 6 |
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 | KRX-0502 |
|---|---|---|
| Participants analysed | 32 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 8 |
| Age, Categorical: >=65 years | Participants | 24 |
| Age, Continuous | years | 69.3 (SD 12.47) |
| Sex: Female, Male: Female | Participants | 15 |
| Sex: Female, Male: Male | Participants | 17 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 32 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 31 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Hemoglobin From Baseline to the End of 8-week Treatment Period, measured over 8 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | g/dL |
| Endpoint classification | Continuous Endpoint |
Hemoglobin is a continuous measurement, and the primary endpoint asks how its mean changed from the start of the study to the end of the 8-week treatment period. Expressing change in g/dL gives a common scale for describing the direction and size of the within-group observation. The registry identifies the summary as a mean and names standard deviation as the dispersion measure.
In general, a mean summarizes the central value of measurements, while a standard deviation describes how much individual observations vary around that mean. Both can help readers understand a group’s outcome: the mean describes the average change, and the spread indicates whether participants’ changes were relatively similar or varied. A mean alone does not show the distribution of individual responses.
For this endpoint, the clinically and statistically relevant numerical result would include the mean change and a measure of uncertainty. Neither the numerical mean nor its standard deviation is reported in the registry record. The record also does not clarify which participants’ measurements contributed to the endpoint or how missing measurements were handled. As a result, the endpoint definition is available, but its observed magnitude and precision cannot be assessed from the posted registry information.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes that the investigators planned to assess mean hemoglobin change over an 8-week treatment period in a single group receiving KRX-0502 without food. It does not report the numerical primary outcome. Consequently, the direction and size of the observed mean change, its variability, and its statistical precision are not reported in the registry record. A conclusion about the observed hemoglobin pattern cannot be drawn from the endpoint description alone.
The distinction between a defined outcome and a reported result is important. Naming an endpoint tells readers what was intended to be measured; it does not establish what the measurements showed. The registry identifies standard deviation as the dispersion measure, but gives no value for it. A confidence interval, if reported, would describe the range of estimates compatible with the data under the specified statistical method. Such an interval is not reported in the registry record, so the precision of the estimate cannot be judged.
The single-group design also limits what a change from baseline can establish. A before-and-after observation describes how the measured outcome changed over time among participants with available data. Without a concurrent control group, that change cannot be separated from other explanations, such as ordinary variation over time, changes in care, or differences in who had measurements available at each assessment. These are general interpretive considerations, not findings about what happened in this study.
The registry lists 32 enrolled participants, but does not report the number included in the primary outcome analysis. It also lists no analyses. The absence of a listed analysis does not establish which analyses were conducted elsewhere; it means the registry record does not document them. The record does not report a p-value or other inferential result for the primary endpoint.
Safety information is recorded separately: the KRX-0502 group has serious-event and other-event counts, along with a death count and several serious-event terms. Those observations describe what the record lists, but they do not supply the missing primary efficacy result. Nor do event counts in a single group, without a comparator and further context, establish whether events were caused by the intervention. Overall, the posted information supports a description of the study’s design and recorded safety counts, but not a quantitative interpretation of its primary outcome.
9. Statistical Methods Explained
The endpoint is a change score: a measurement at the end of the stated treatment period is considered relative to baseline for each participant, and the group result is described as a mean. In general, a change-score analysis uses the paired nature of measurements from the same participant. It is not the same as comparing two independent groups. The registry record names the endpoint and its summary type, but does not report the numerical result or the specific statistical procedure used to analyze it.
What does the mean describe?
In general, the mean is the arithmetic average of the observed values included in an analysis. For a change endpoint, the average change describes the group’s central before-and-after pattern. It does not imply that every participant changed by that amount. Some individual changes may be smaller, larger, or in a different direction. The standard deviation helps describe variation in the individual changes, but the record does not provide its value or clarify whether it refers specifically to the change scores.
How should uncertainty be understood?
In general, an estimate is subject to sampling uncertainty because it is based on observations from a study group rather than every person in the target population. A confidence interval conveys uncertainty around an estimate under a particular model and analysis. A narrower interval generally indicates greater precision, while a wider interval indicates less precision. A confidence interval for the primary outcome is not reported in the registry record. Without an estimate and its uncertainty, readers cannot assess how precisely the study describes the mean change.
A p-value, when used, addresses how compatible the observed data are with a specified null hypothesis under the statistical model. It is not a measure of clinical importance and does not give the probability that a treatment works. The registry record does not report a p-value or identify a primary-endpoint hypothesis test. The reported design is a single group, so there is no randomized between-group treatment contrast to interpret.
What does the design allow?
In general, a single-group before-and-after analysis can describe change over time among participants who contribute measurements. It cannot by itself distinguish a treatment-associated change from other time-related or measurement-related influences. A concurrent control group can help address some of those influences when appropriately designed and analyzed; no such group is recorded for this study. The design should therefore be read as a pilot assessment within one treated group, not as a randomized comparison.
Allocation is listed as NA and masking as none. The record does not report details of endpoint assessment, adherence measurement, covariate adjustment, or the handling of repeated or incomplete measurements. No particular analysis method, such as a paired test or a model-based approach, should be assumed from the endpoint description alone.
How does variability affect interpretation?
In general, a standard deviation describes variability among observed values, whereas a standard error describes uncertainty in an estimated mean. They are not interchangeable. The registry identifies standard deviation as the dispersion type, but does not report a value. For outcomes with more variability than a simple model assumes, methods that account for over-dispersion may be needed; this is a general point about statistical modeling and does not imply that over-dispersion was present or relevant to this continuous endpoint.
For continuous outcomes, distributional assumptions can affect standard errors, confidence intervals, and tests. A reader would need the outcome data or fuller analysis details to assess those assumptions. The registry record does not report distribution checks, model diagnostics, or a statistical analysis plan. No assumption about normality or the suitability of a particular test can be made from the listed endpoint alone.
How should planning figures be read?
In general, a sample-size calculation is a planning exercise about the amount of information that might be needed to detect a specified effect under stated assumptions. It is not a measure of the study’s observed power and does not replace the observed estimate and its uncertainty. The stated planning convention describes a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation, with effects framed as fractions of an observed effect. It also specifies participants per arm for these non-time-to-event illustrations.
Those planning assumptions describe a hypothetical two-arm framework, while the registered study is single group. They should not be mistaken for the actual allocation or observed design of this pilot study. The registry record does not report the numerical planning values or a sample-size justification from the study protocol. Planning values cannot establish that an observed effect was precise, nor can they resolve the absence of a reported primary outcome result.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 1 outcome measure and 0 analyses. The primary outcome is mean change in hemoglobin from baseline to the end of the 8-week treatment period. No additional outcome analysis or inferential result is listed. The record does not report whether the investigators prespecified a hierarchy of outcomes, adjusted for multiple testing, or used any other multiplicity procedure. Those details are not reported in the registry record.
In general, multiplicity arises when several outcomes, time points, subgroups, or statistical tests are evaluated. When many tests are considered, the chance of at least one apparently notable result can increase unless the analysis plan addresses that issue. This is a general statistical concern, not evidence that multiple testing occurred in this study. The absence of listed analyses is not enough to determine what analyses were performed beyond the registry entry.
Missing-data handling is also not reported in the registry record. The record does not state how many participants had endpoint measurements, whether measurements were missing, why they might have been missing, or whether any imputation or sensitivity analysis was used. A complete-case estimate and an estimate using an imputation method can answer different questions, particularly if missingness is related to outcome or participant characteristics. No approach should be assumed.
The analysis population is not reported in the registry record. Although 32 participants are listed as enrolled, that does not establish how many contributed data to the primary endpoint or which analysis set was used. The record does not specify whether the primary analysis was based on all enrolled participants, participants who started treatment, or participants with observed measurements. These gaps limit reproducibility and make it difficult to judge how the endpoint summary relates to enrollment.
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 |
|---|---|---|---|
| KRX-0502 | 2 | 32 | 6.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| KRX-0502 | 1 of 32 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| KRX-0502 | 25 of 32 |
Most frequent serious adverse event terms
| Event term | Organ system | KRX-0502 |
|---|---|---|
| Rib Fracture | General disorders | 1 of 32 |
| Urinary Tract Infection | General disorders | 1 of 32 |
| General Physical Health Deterioration | General disorders | 1 of 32 |
| Cardiac Failure Chronic | Cardiac disorders | 1 of 32 |
Most frequent non-serious adverse event terms
| Event term | Organ system | KRX-0502 |
|---|---|---|
| Diarrhoea | Gastrointestinal disorders | 9 of 32 |
| Faeces Discoloured | Gastrointestinal disorders | 8 of 32 |
| Abdominal Pain | Gastrointestinal disorders | 6 of 32 |
| Constipation | Gastrointestinal disorders | 3 of 32 |
| Abdominal Discomfort | Gastrointestinal disorders | 2 of 32 |
| Vomiting | Gastrointestinal disorders | 2 of 32 |
| Weight Decrease | Investigations | 2 of 32 |
| Hyperkalaemia | Metabolism and nutrition disorders | 2 of 32 |
| Hypocalcaemia | Metabolism and nutrition disorders | 2 of 32 |
| Dizziness | Nervous system disorders | 2 of 32 |
Serious events with the highest arm-level rate: rib fracture (3.1%), urinary tract infection (3.1%), general physical health deterioration (3.1%), cardiac failure chronic (3.1%).
The registry lists the KRX-0502 group with 32 participants at risk in the serious-event count, 2 affected by serious events, and 32 at risk in the other-event count, with 25 affected. It also records 1 death. These are counts recorded for this single group; the registry record does not provide a comparator group for evaluating relative event frequency.
The listed serious-event terms are Rib Fracture, Urinary Tract Infection, General Physical Health Deterioration, and Cardiac Failure Chronic, each recorded as 3.1%. These terms describe entries in the registry, not an assessment of cause. The record does not establish that any event was caused by KRX-0502. It also does not provide timing, participant-level overlap between terms, event duration, or additional clinical context.
Serious events and other events are separate registry categories, and the affected counts should not be added together. A count of affected participants is not necessarily the same as a count of individual event episodes. The record does not report enough detail to infer event rates over time or compare safety with another treatment. These numbers describe the entries in the registry record and should be interpreted as descriptive observations from a single-group study.
12. What the Result Does, and Does Not, Mean
The study addresses a specific statistical question: how mean hemoglobin changed from baseline to the end of an 8-week period among participants receiving ferric citrate without food. The record identifies a population with stage 3-5 non-dialysis dependent chronic kidney disease and describes the study as a Phase 2 pilot. However, the numerical result for the primary endpoint is not reported in the registry record. The direction, magnitude, and precision of the observed mean change therefore cannot be stated.
Even if a within-group change were available, it would describe change during the study rather than prove that the intervention caused that change. In general, a single-group before-and-after design cannot separate the intervention’s contribution from other explanations for change over time. The absence of a comparator is especially relevant when interpreting an apparent improvement or worsening; neither pattern alone would provide a controlled estimate of an intervention effect.
The registry’s safety entries also have a limited interpretation. They record serious-event and other-event counts, listed serious-event terms, and a death count for the treated group. They do not establish causation or provide a comparative assessment. The record does not report enough detail to interpret timing, overlap, or exposure-adjusted event frequency.
Accordingly, the registry entry can be used to understand the study question, design, outcome definition, and recorded safety counts. It cannot support a quantitative statement about the primary hemoglobin result or a causal comparison with another treatment. The missing outcome estimate, uncertainty measure, analysis details, and analysis population should remain explicit when drawing conclusions from this record.
13. Why This Trial Matters Statistically
This study is statistically notable as a pilot evaluation of a continuous before-and-after outcome in a single treated group. Its design makes the estimand and comparator question central: a mean change over time is not the same quantity as a treatment effect relative to a control. Keeping those questions distinct helps prevent a within-group observation from being interpreted as a randomized contrast.
The registry identifies the primary endpoint and the intended summary approach, but does not report the outcome estimate or its variability. That gap illustrates why transparent reporting needs more than an outcome title. A numerical estimate, an uncertainty measure, the analysis population, and a description of missing-data handling are all important for understanding what the observed data can support.
The listed enrollment and safety counts provide some descriptive context, but do not substitute for the missing primary result or a comparator. Likewise, statistical planning illustrations are not observed evidence: planning assumptions concern what a hypothetical design might detect, not what this single-group study demonstrated. In general, separating planning, estimation, and causal interpretation is essential for sound reading of clinical-trial statistics.
The record also shows why registry entries should be interpreted narrowly. It documents a Phase 2 study, a single-group design, and the endpoint definition, but does not document a statistical analysis or numerical primary outcome. Recognizing the boundary between what is recorded and what is not reported is a basic part of evidence appraisal.
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 main limitation for statistical interpretation is that the numerical primary endpoint result is not reported in the registry record. The mean change, standard deviation, confidence interval, and p-value are not reported, so neither the observed magnitude nor its precision can be evaluated. The record also lists 0 analyses, leaving the statistical procedure for the primary outcome undocumented.
The single-group design has no concurrent control arm, so the endpoint is a within-group change rather than a randomized treatment contrast. This limits causal interpretation even if the numerical result were available. Allocation is listed as NA and masking as none; further design details are not reported in the registry record.
The enrolled number is 32, but the analysis population and the number contributing endpoint measurements are not reported in the registry record. Missing-data frequency, reasons for missingness, and methods for handling missing measurements are also not reported. Without those details, it is not possible to determine how the endpoint summary relates to enrollment or whether missing observations could affect its interpretation.
Additional details that are not reported in the registry record include dose and schedule, adherence, eligibility criteria, the protocol’s statistical plan, sample-size justification, covariate adjustment, and outcome-assessment procedures. The safety record offers counts and listed terms, but lacks comparative and event-level context needed to assess causality or time-adjusted frequency. These limitations concern what can be concluded from the registry entry; they do not establish that information is absent from other study documents.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Pilot Study of KRX-0502 (Ferric Citrate, Administered Without Food, in Treating Iron-deficiency Anemia — NCT02128074.
- Registry record last updated 2018-08-24; status last verified 2017-11.
- Results first posted 2018-08-24.
- 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
NCT02128074 is a completed Phase 2 pilot study sponsored by Keryx Biopharmaceuticals. It evaluated KRX-0502, identified as ferric citrate and administered without food, in patients with stage 3-5 non-dialysis dependent chronic kidney disease and iron-deficiency anemia. The record lists 32 enrolled participants and a single-group design, with allocation listed as NA and masking as none.
The primary endpoint was mean change in hemoglobin from baseline to the end of the 8-week treatment period, with standard deviation identified as the dispersion measure. The numerical outcome and statistical analysis are not reported in the registry record. The record lists serious-event and other-event counts, 1 death, and four serious-event terms each recorded as 3.1%. These are descriptive entries from a single group and do not establish causation or provide a controlled comparison.