Quantitative Mass Transfer of SFP-iron From Dialysate to Blood in CKD-HD Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Quantitative Mass Transfer of SFP-iron From Dialysate to Blood in CKD-HD Patients (NCT01894906), a randomized phase 1, phase 2 study. The primary outcome is Net Iron Delivery From SFP Via the Dialysate.

2. Clinical Question

The study also set out to examine whether conditions that may influence transfer—including blood and dialysate flow rates, bicarbonate delivery, dialyzer membrane type, and dialyzer reuse—were associated with differences in iron transfer. The listed secondary outcomes cover comparisons with reference hemodialysis, serum iron pharmacokinetics and exploratory modeling, and iron concentrations in dialysate entering and leaving the dialyzer.

This is a measurement-focused question. It concerns the amount of iron transferred during dialysis, rather than a clinical outcome or a comparison of long-term health effects. The registry record does not report numerical findings for the primary or secondary outcomes, so the size and precision of any observed transfer cannot be assessed from the reported information.

3. Trial Design

The registry describes a randomized, non-masked, crossover study in patients with kidney failure receiving hemodialysis. It lists the study as Phase 1 and Phase 2, with an enrollment of 12. The record gives a start of 2013-07, a primary completion of 2013-09, and a completed status. Rockwell Medical Technologies, Inc. is listed as the sponsor.

In a crossover design, participants receive more than one treatment condition, so measurements may be compared within the same person as well as across conditions. Here, the arm descriptions state that each subject would receive one control treatment and five treatments with SFP added to dialysate. The SFP treatments were described as covering different conditions that could affect intradialytic iron transfer. The registry names conditions including membrane type, blood and dialysate flow, bicarbonate delivery, and dialyzer reuse. The available arm descriptions are incomplete, so the full specification of each treatment condition is not reported in the registry record.

The primary outcome is tied to a reference hemodialysis condition identified as Treatment B: SFP, a new membrane, high Qb/Qd, and 37 mEq bicarbonate. Expended dialysate was to be collected at intervals during the session, with aliquots analyzed for iron content, and mean cumulative net iron delivery reported. The record does not describe the randomized treatment sequence, any washout arrangements, or how period and carryover effects were addressed.

Masking is listed as none. The record therefore does not describe blinded treatment assignment or outcome assessment. It identifies the study as completed but does not provide numerical primary outcome results, a detailed statistical analysis plan, or a participant flow account. Additional eligibility criteria and demographic characteristics 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

Analysis population for the primary outcome, as defined in the registry: For this preliminary and explorative study, no prospective calculations of statistical power were made; statistics were descriptive only. All subjects were included in the calculation of all study outcomes.

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: No prospective calculations of statistical power were made. The sample size of 12 subjects (N = 6 for each of 2 dialysis membrane groups) was selected to provide information on safety and to provide preliminary data for assessing the variance of iron delivery under different, pre-specified dialysis conditions.

6. Primary Endpoint

The registry lists the primary outcome as Net Iron Delivery From SFP Via the Dialysate, measured over one dialysis session (approximately 4 hours).

The primary endpoint is net iron delivery from SFP via the dialysate, reported as a mean amount in micrograms. It is intended to quantify SFP-derived iron transferred from dialysate during one dialysis session, rather than simply describe the iron concentration in one sample. The registry specifies that the primary measurement concerns the reference hemodialysis treatment: Treatment B, with SFP, a new membrane, high Qb/Qd, and 37 mEq bicarbonate.

The planned collection covers expended dialysate at intervals across the session, and aliquots are analyzed for iron content. The record says that mean cumulative net iron delivery will be reported. The stated timeframe is one dialysis session, approximately 4 hours. This measure aligns directly with the study's stated purpose of quantifying iron transfer from dialysate to patients during dialysis. The listed secondary outcomes separately address iron concentrations entering and leaving in dialysate and serum iron pharmacokinetics.

As a general statistical point, an amount accumulated over a session answers a different question from a concentration measured at a single time or location. A mean describes the average observed amount in the analyzed group; a measure of spread or an interval estimate would help convey how variable or uncertain that mean is. The registry identifies standard deviation as the dispersion measure for the primary outcome, but it does not report the mean, standard deviation, or an interval estimate. The endpoint's numerical result and its precision are therefore not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a continuous measurement summarized by a mean and standard deviation. A continuous outcome can take values along a scale, in this case an amount of iron measured in micrograms. The mean gives a measure of the center of the observed values. The standard deviation describes how dispersed those values are around the mean. Neither statistic is reported numerically for the primary endpoint, so the observed central amount and variability cannot be assessed.

What does a mean describe?

As a general explanation, a mean combines measured values into an average. It can provide a compact description when the measurement is meaningful on a quantitative scale, but it does not show the full distribution. Different patterns of individual measurements can have the same mean. The accompanying standard deviation adds information about spread, but it also does not describe every feature of a distribution. In this study, the intended mean is cumulative net iron delivery for the reference hemodialysis condition. The record does not give the underlying observations or numerical summary.

Why does the crossover design matter?

In a crossover study, the same participant can contribute observations under more than one treatment condition. As a general statistical principle, observations from one person are related rather than independent. An analysis of treatment conditions may need to account for that within-person relationship. A comparison that ignores it can misrepresent uncertainty. The registry identifies the design as crossover but does not report the treatment sequence, period structure, or model used to handle repeated observations. Those details are important for understanding any condition comparisons, but they are not reported in the registry record.

The record says each subject would receive one control treatment and five SFP treatments, with the SFP conditions differing in factors that could affect iron transfer. It does not state how treatment order was randomized or whether a washout period was used. Nor does it describe whether the primary analysis used paired differences, a repeated-measures model, or another method. These methods cannot be inferred from the design label alone.

What does descriptive analysis imply?

The registry states that the study was preliminary and exploratory, that no prospective statistical power calculations were made, and that statistics were descriptive only. Descriptive statistics summarize the observations; they do not, by themselves, quantify evidence against a hypothesis or establish a treatment effect. General inferential methods can use standard errors, confidence intervals, or hypothesis tests, but no such primary outcome results are reported in the registry record. The record also does not report a formal sample-size justification or an analysis plan detailing inferential procedures.

Power is a design concept related to the chance that a planned test will detect a specified effect under stated assumptions. Because the record says no prospective power calculations were made, there is no reported prospective power basis for interpreting the enrollment. The enrollment of 12 is not a measure of observed power and does not reveal the precision of the missing result. Without the outcome estimate and its variability, it is not possible to assess the precision actually achieved.

How should uncertainty be read?

As a general explanation, a standard deviation describes variation among measured observations, while a confidence interval describes uncertainty about an estimated quantity under a statistical model. They answer related but distinct questions. A narrow confidence interval would indicate greater precision under the method's assumptions; a wide interval would indicate less precision. No confidence interval is reported for the primary endpoint, and no uncertainty estimate can be reconstructed from the registry's description alone.

Over-dispersion is a general concern when observed variability exceeds what a model assumes. It is particularly relevant to some count or event data models. The primary endpoint is described as a continuous amount, and the registry gives no distributional diagnostics or model specification. There is therefore no basis in the record to characterize over-dispersion or to claim that it was assessed. More generally, assumptions about the distribution and dependence structure cannot be checked without data and analysis details.

What can be concluded from the analysis record?

The registry lists five outcome measures and zero analysis entries. The absence of analysis entries does not establish that no analysis was conducted; it means analysis details and results are not reported in the registry record. The stated descriptive-only approach is the available characterization of the study's statistics. The primary result, condition-specific comparisons, handling of repeated observations, and estimates of uncertainty remain unavailable.

The primary outcome's collection plan includes expended dialysate over specified intervals during a session and laboratory analysis of aliquots. These procedures describe how measurements were intended to be obtained, not how missing or unusable measurements were handled. The registry does not describe quality control, limits of quantification, handling of measurements below a detection threshold, or prespecified exclusions. Such details would matter when interpreting an assay-based amount, but they are not reported.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Treatment B")
n   <- c(12)
m   <- c(692)
sp  <- c(1010)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Treatment B  12  692.000  1010.000  50.277  1333.723

11. Multiplicity, Missing Data and Analysis Populations

The study includes a primary outcome and five listed outcome measures, along with multiple SFP treatment conditions. In general, examining several outcomes or treatment comparisons creates a multiplicity issue: the more questions considered, the more important it is to distinguish prespecified primary analyses from exploratory ones and to describe any adjustment or interpretive strategy. The registry characterizes the study as preliminary and exploratory, but a method for addressing multiplicity is not reported in the registry record.

The listed secondary outcomes include comparisons of SFP-derived iron administered under various conditions with reference hemodialysis, serum iron pharmacokinetics and exploratory modeling, and dialysate iron concentrations entering and leaving. Numerical results and analysis details for these outcomes are not reported. It is not possible to determine which contrasts were conducted, whether any were prioritized, or whether a multiplicity adjustment was used.

The primary outcome description says all subjects were included in the calculation of all study outcomes. This states an intended analysis population, but it does not explain whether every participant contributed usable data to every measure or how missing observations were handled. Reasons for missingness, the amount of missing data, imputation, and sensitivity analyses are not reported in the registry record.

The record does not describe analysis populations such as intention-to-treat or per-protocol populations, nor does it explain exclusions after enrollment. It also does not report how crossover-specific incomplete treatment sequences would be handled. These omissions limit assessment of whether the outcome summaries include all enrolled participants and how missing measurements might affect comparisons.

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 non-serious adverse event terms

The registry reports serious adverse events by treatment condition. The serious-adverse-event counts are 0 among 12 at risk for Control, Treatment B, Treatment C, Treatment D, Treatment E, and Treatment F. These are descriptive counts for the listed conditions. They do not establish that serious events could not occur, and they should be read in light of the study's enrollment and the information recorded.

For other adverse events, the reported affected counts are 1 among 12 at risk for Control, 2 among 12 for Treatment B, 2 among 12 for Treatment C, 1 among 12 for Treatment D, 2 among 12 for Treatment E, and 0 among 12 for Treatment F. The registry does not provide event descriptions or clarify whether an affected participant could contribute events under more than one condition. In a crossover study, the same person can receive multiple conditions, so the condition-specific counts should not be interpreted as counts from independent groups of people.

Death counts are not reported in the registry record; a blank death field is not evidence of zero deaths. The record also does not report the timing, severity detail, relatedness assessment, or complete event narratives. These limitations mean the counts alone cannot characterize the nature or comparative safety profile of the conditions.

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

The study asks a focused measurement question: how much SFP-derived iron is delivered net from dialysate during a dialysis session under a specified reference condition, and how selected dialysis conditions may relate to transfer. The registry describes the planned endpoint and a crossover design suited to measuring multiple conditions in the same participants. However, it does not report the numerical primary endpoint result or the condition-specific comparisons.

Accordingly, the record supports an account of what the investigators intended to measure, not a conclusion about the amount of iron transferred. It does not establish the observed mean, the variation among participants, or the precision of the estimate. Without those results, the size and direction of any differences between treatment conditions cannot be determined. The descriptive-only statistical characterization also does not support claims about statistical significance.

As a general interpretation, a measurement of transfer during a session is not itself a measure of longer-term clinical outcomes. The registry's primary endpoint concerns net iron delivery over one session, approximately 4 hours. The listed secondary outcomes include serum iron and dialysate concentration measures, but the record does not report their findings. No claim about clinical benefit, harm, or long-term effects follows from the endpoint description alone.

The crossover design and enrollment of 12 describe the structure and size of the study, but do not resolve the missing-result problem. Interpretation of comparisons would also depend on treatment order, period effects, carryover, and the analysis of repeated observations; these details are not reported in the registry record. The safety counts offer limited descriptive information, while event details and death counts are unavailable.

The most defensible reading is therefore narrow: this completed, randomized, non-masked study was designed to quantify SFP-derived iron transfer under different dialysis conditions, but its registry record does not report the numerical outcome findings needed to judge what was observed or how precisely it was estimated.

14. Why This Trial Matters Statistically

Statistically, this trial is notable for framing iron transfer as a quantitative measurement and for using a crossover design to examine more than one dialysis condition in the same participants. That structure can be informative when treatment conditions are compared within individuals, because participant-level characteristics are shared across those observations. It also requires analysis that recognizes the dependence among repeated measurements. The registry identifies the design but does not report the method used to account for that dependence.

The study description distinguishes a reference condition from other SFP conditions and names factors that may influence transfer. This makes the estimand—the quantity being summarized—important. The primary endpoint is mean cumulative net iron delivery under the reference hemodialysis condition, not a general estimate across every possible dialysis setting. Clear specification of the condition helps define what the outcome is intended to represent.

The record also illustrates why design and result reporting are separate parts of evidence. It describes randomization, masking, outcome measurement, and the exploratory descriptive approach, but does not give the primary mean or its variability. Without the result, readers cannot evaluate the magnitude or precision of the measurement. Without analysis details, readers cannot judge how condition comparisons accounted for repeated observations or multiplicity.

The stated absence of prospective power calculations is relevant to interpretation. The enrollment should not be read as evidence that the study was sized to detect a particular effect, and the record does not provide a formal sample-size justification. In an exploratory measurement study, transparent estimates and uncertainty are especially useful for understanding what the data can and cannot establish. Those numerical findings are not reported in the registry record.

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 central limitation for interpreting this trial is that the registry record describes the primary endpoint but does not report its numerical result. The primary mean, standard deviation, and any interval estimate are not reported in the registry record. Secondary outcome results are also not reported, preventing assessment of the planned comparisons and iron concentration measurements.

The enrollment was 12, and the registry states that no prospective power calculations were made. This was described as a preliminary and exploratory study with descriptive statistics. The record does not provide a sample-size justification or estimates of precision. The study's size and exploratory purpose should therefore be kept in view without treating enrollment as proof of adequate power or as observed power.

Although the study is identified as randomized and crossover, key design and analysis details are not reported: the treatment sequence, period structure, washout arrangements, and handling of possible carryover or period effects. The non-masked design is stated, but the record does not describe outcome-assessment procedures that might affect measurement. The arm descriptions are incomplete, limiting reconstruction of the exact conditions across all treatments.

Data handling is also unclear. The record says all subjects were included in calculation of all outcomes, but does not report missing observations, exclusions, assay limitations, or how unusable measurements were handled. It does not describe the statistical model, confidence intervals, hypothesis tests, or any approach to multiplicity across conditions and outcomes. These gaps prevent independent assessment of the reliability and scope of potential comparisons.

Finally, the safety record gives condition-specific counts but does not report event descriptions or death counts. The record therefore offers limited information for understanding the nature of reported events or interpreting safety across the crossover conditions.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Quantitative Mass Transfer of SFP-iron From Dialysate to Blood in CKD-HD Patients — NCT01894906.
• Registry record last updated 2015-02-16; status last verified 2015-01.
• Results first posted 2015-01-09.
• 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

This completed Phase 1 and Phase 2 study was randomized, non-masked, and crossover, with 12 enrolled patients receiving hemodialysis. Each subject was described as receiving one control treatment and five SFP treatments under varying dialysis conditions. The primary endpoint was mean cumulative net iron delivery from SFP via dialysate during one session, approximately 4 hours, under a specified reference condition.

The registry states that the study was preliminary and exploratory, with descriptive statistics and no prospective power calculations. It does not report the numerical primary endpoint result, its variability, or secondary outcome findings. It also does not describe treatment sequence, missing-data handling, or the statistical methods used for crossover comparisons. Serious adverse event counts were 0 among 12 at risk in each listed condition; death counts are not reported in the registry record.