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 Comparative Effects Of Dialysate Flow Rate And Membrane Packing On The Performance Of Dialyzers Used For Hemodialysis (NCT00636077), a randomized na study. The primary outcome is Effect of Increased Dialysate Flow Rate on KoA for Urea Between 4 Dialyzers With Different Membrane Packing Densities..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00636077 |
| Phase | NA |
| Condition | Chronic Kidney Disease, Chronic Renal Disease |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 12 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Vantive Health LLC |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled 12 people with chronic kidney disease or chronic renal disease who were receiving clinical hemodialysis. Further eligibility details and participant characteristics are not reported in the registry record.
Intervention
The study assessed four dialyzers with different membrane packing densities. Each device was used at three dialysate flow rates, and transfer of urea, phosphorus, and beta-2-microglobulin from blood to dialysate was measured.
Comparator
The comparisons concern performance across the four dialyzers and across dialysate flow rates. The record does not give the actual flow-rate values or a single designated reference dialyzer.
Primary question
The primary question was whether increased dialysate flow rate affected KoA for urea across dialyzers with different membrane packing densities. KoA describes dialyzer efficiency for urea removal. The broader study purpose was to assess whether packing density relates to performance and whether that relationship depends on flow rate.
This is a device-performance question, not a comparison of clinical outcomes between treatment strategies. The stated measurements concern the transfer of molecules during hemodialysis. The registry record does not report numerical results for the primary comparison, so the direction and size of any observed differences cannot be assessed from the posted record.
3. Trial Design
The registry describes a randomized, unmasked crossover study with enrollment of 12 participants. A crossover design means that participants receive more than one study condition, allowing measurements under different conditions to be compared within the same person. This can account for stable participant characteristics when the analysis appropriately handles the repeated observations.
The study involved four dialyzers: Polyflux HD-C4 Big, HD-C4 Small, Optiflux 160NR, and Optiflux 200NR. The arm descriptions refer to HD-C4 Big, HD-C4 Small, F160NR, and F200NR, respectively. Each arm description states that the named dialyzer was used for 3 consecutive treatments. The summary also says each of the four dialyzers was used at three different dialysate flow rates.
The primary measurement was scheduled during the third treatment with each dialyzer, one time during each trial period week. The registry does not detail the order in which participants received the devices or flow rates, how treatment periods were scheduled, or whether any washout or stabilization interval was used. Those design details are not reported in the registry record.
The study status is completed. Its recorded start was 2008-02, and primary completion was 2008-04. The registry lists no masking. It does not report a phase beyond NA, nor does it describe the randomization sequence or concealment procedures. The enrollment figure does not by itself establish how many complete measurements were available for each device and flow-rate condition.
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.
Week 1
| Stage | HD-C4 Big First | HD-C4 Small First | Optiflux F160NR First | Optiflux F200NR First |
|---|---|---|---|---|
| STARTED | 3 | 3 | 3 | 3 |
| COMPLETED | 3 | 3 | 3 | 3 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
Week 2
| Stage | HD-C4 Big First | HD-C4 Small First | Optiflux F160NR First | Optiflux F200NR First |
|---|---|---|---|---|
| STARTED | 3 | 3 | 3 | 3 |
| COMPLETED | 3 | 3 | 3 | 3 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
Week 3
| Stage | HD-C4 Big First | HD-C4 Small First | Optiflux F160NR First | Optiflux F200NR First |
|---|---|---|---|---|
| STARTED | 3 | 3 | 3 | 3 |
| COMPLETED | 3 | 3 | 3 | 3 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
Week 4
| Stage | HD-C4 Big First | HD-C4 Small First | Optiflux F160NR First | Optiflux F200NR First |
|---|---|---|---|---|
| STARTED | 3 | 3 | 3 | 3 |
| COMPLETED | 3 | 3 | 3 | 3 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
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 | All Study Participants |
|---|---|---|
| Participants analysed | 12 | |
| Age, Continuous | Years | 60 (32 to 83) |
| Sex: Female, Male: Female | Participants | 9 |
| Sex: Female, Male: Male | Participants | 3 |
6. Primary Endpoint
The registry lists the primary outcome as Effect of Increased Dialysate Flow Rate on KoA for Urea Between 4 Dialyzers With Different Membrane Packing Densities., measured over During the third treatment with each dialyzer (one time during each trial period week).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | KoA for urea (mL/min) |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is KoA for urea, measured in mL/min. The registry describes KoA as a constant indicating how efficiently a dialyzer removes urea. It is determined by the membrane surface area, membrane thickness, and pore size. In this study, the endpoint was intended to assess whether urea-transfer performance changed with dialysate flow rate and whether the pattern differed among dialyzers with different membrane packing densities.
The measurement was scheduled during the third treatment with each dialyzer, one time during each trial period week. The listed summary measure is the mean, with standard error as the dispersion measure. In general, the mean gives a measure of the central value, while the standard error describes uncertainty in the estimated mean; it is not a direct description of the spread of individual participant values.
The endpoint is a physiologic and device-performance measure, rather than a patient-centered clinical outcome. Although the study summary also names phosphorus and beta-2-microglobulin transfer, the primary endpoint specified in the record concerns KoA for urea. The registry does not report numerical endpoint values, confidence intervals, or a test of the primary comparison. Therefore, the recorded endpoint definition alone does not establish the magnitude or precision of any difference.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a focused comparison of dialyzer performance under differing flow-rate and membrane-packing conditions. Its crossover structure could support within-participant comparisons, because each participant may contribute measurements under multiple conditions. The statistical interpretation would depend on how those repeated measurements were analyzed and on whether the measurements were complete and comparable across conditions. The registry record does not report the analysis method or numerical results needed to evaluate these points.
The primary outcome is defined as mean KoA for urea with standard error. No values for the means or standard errors are reported in the registry record. No confidence intervals, p-values, estimated contrasts, or other results for the primary comparison are reported. As a result, the posted record does not show whether the observed measurements differed across flow rates or dialyzers, how large any differences were, or how precisely they were estimated.
The record states that 12 participants enrolled and that the primary measurement was scheduled during the third treatment with each dialyzer. Enrollment is not the same as the number of participants with complete outcome measurements in every condition. Completion counts and reasons for missing measurements are not reported in the registry record. The reported enrollment therefore cannot be taken as proof that all scheduled measurements were collected and analyzed.
The record lists 6 outcome measures and no analyses. Its primary outcome entry includes a timeframe and a mean with standard error, but the outcome values themselves are not reported. The study summary describes measurement of three molecules, while the title and primary endpoint focus on KoA for urea. Without results and analysis details, the intended comparisons cannot be reconstructed from the registry entry.
These limitations are about what can be interpreted from the registry record, not proof that no results were collected elsewhere. The record does not report a protocol-level statistical plan, a prespecified primary contrast beyond the endpoint title, or a rationale for the enrollment target. Consequently, neither the observed effect nor its statistical uncertainty can be characterized from the posted information. Any numerical planning illustrations should be understood as planning calculations rather than observed power, and cannot substitute for reported outcome estimates.
9. Statistical Methods Explained
The statistical methods described in the registry record are limited. It identifies a randomized crossover design, a continuous primary measure, the mean as the summary parameter, and standard error as the dispersion measure. It does not report the model or test used to compare dialyzers and flow rates. The following concepts explain how such features are generally interpreted; they do not identify methods actually used in this trial.
What does a crossover design imply for analysis?
In a crossover study, an individual can contribute measurements under multiple conditions. General statistical practice accounts for the fact that measurements from the same person are related rather than independent. A paired comparison or a repeated-measures model can use this structure, depending on the design and question. Treating every measurement as if it came from a different participant can misrepresent uncertainty because within-person observations often share participant-specific influences. The registry record does not report whether the analysis accounted for these dependencies.
Period and order can also matter in crossover studies. A participant’s measurement may be affected by when a condition was received or by the condition received previously. Randomization can help distribute order effects, but the randomization sequence, period effects, and any carryover assessment are not reported in the registry record. The entry also does not describe washout procedures. These omissions prevent a reader from determining how such potential influences were handled.
What do mean and standard error convey?
The mean summarizes the central level of a continuous measure. Standard error describes the precision of an estimated mean under the assumptions of the analysis. It is not the same as standard deviation: standard deviation describes variation among individual measurements, whereas standard error describes uncertainty in an estimate. A confidence interval is a range calculated by a statistical procedure to express uncertainty around an estimate. No confidence intervals or numerical standard errors for the primary outcome are reported in the registry record.
When comparing conditions, the estimate of the difference and its confidence interval are often more informative than separate means alone. In a crossover study, that comparison should reflect the paired or repeated nature of observations. The record supplies no outcome estimates or interval estimates, so neither the size of the condition contrasts nor their precision can be evaluated.
Why can over-dispersion matter?
In general, over-dispersion occurs when observed variation is greater than a statistical model expects. It can make standard errors too small if the model assumes less variability than the data contain. This concern is especially relevant to some count outcomes; the primary endpoint in this study is continuous, and the registry record does not identify an over-dispersion model or report a diagnostic assessment. No claim about over-dispersion in these data can be made from the record.
What does the record establish about the analysis?
The registry lists 6 outcome measures and no analyses. It identifies the primary measure as mean KoA for urea, with standard error, but does not specify a statistical test, model, covariate adjustment, handling of repeated observations, or approach to missing values. The detailed statistical analysis plan is not reported in the registry record. It is therefore not possible to determine whether the planned analysis accounted for the crossover structure, how the four dialyzers and flow-rate conditions were contrasted, or what inferential criterion was used.
The registry also does not report a sample-size justification. Planning illustrations based on an observed effect are not a report of observed power and do not demonstrate that a study was adequately sized. Any such illustration depends on its assumptions and is not a substitute for the estimated effect and its uncertainty. No numerical illustration values are reported in the registry record, and no sample-size rationale can be inferred from enrollment alone.
10. Multiplicity, Missing Data and Analysis Populations
The study summary describes several measurement dimensions: four dialyzers, three dialysate flow rates, and transfer measurements for urea, phosphorus, and beta-2-microglobulin. The registry lists 6 outcome measures. Considering multiple endpoints, devices, flow rates, or contrasts can create a multiplicity issue: when many statistical comparisons are made, the chance of at least one apparently unusual result can increase. Statistical plans may address this through a designated primary comparison or an adjustment strategy. The registry record does not report a multiplicity procedure or a complete hierarchy of planned comparisons.
The primary outcome title identifies KoA for urea and frames the question around increased dialysate flow rate across four dialyzers. However, the record does not provide the specific flow-rate values or a fully described set of pairwise or overall contrasts. It also does not report a statistical analysis plan. Thus, the extent of the planned multiplicity and how it was handled are not reported in the registry record.
Missing data are another important issue in a crossover design. A participant may have measurements for some conditions but not others; such incomplete records can affect paired comparisons and the assumptions of a model. The registry does not state how many participants had complete measurements, whether any observations were missing, why they might be missing, or how missing measurements were handled. These details are not reported in the registry record.
The analysis population is also not specified. The record does not say whether analyses included all enrolled participants, only those completing the scheduled treatments, or another defined group. It does not report exclusions or participant flow through the treatment periods. Enrollment of 12 alone does not establish the analysis population or the number of evaluable observations. These uncertainties limit interpretation of both the intended comparisons and their representativeness.
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 |
|---|---|---|---|
| HD-C4 Big | 0 | 12 | 0.0% |
| HD-C4 Small | 0 | 12 | 0.0% |
| F160NR | 0 | 12 | 0.0% |
| F200NR | 0 | 12 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| HD-C4 Big | 0 of 12 |
| HD-C4 Small | 0 of 12 |
| F160NR | 0 of 12 |
| F200NR | 0 of 12 |
The adverse-event entry lists 12 participants at risk in each of the four dialyzer groups. For every group, the recorded count with a serious adverse event is 0, and the recorded count with other adverse events is 0. These are the figures entered in the registry record; they should be read as reported counts, not as proof that no events occurred outside the record or that every possible event was captured.
The death fields are null for all four groups. A null entry is not the same as a reported count of zero, so deaths should be described as not reported in the registry record rather than absent. The record does not provide event definitions, observation windows, severity details beyond the serious-event category, or an explanation of how events were collected.
Because this is a crossover study, participants may contribute exposure to more than one dialyzer condition. The repeated group risk counts should not automatically be interpreted as separate sets of unique participants. The record does not explain the safety denominator conventions or whether adverse events were attributed to individual treatment periods. The listed counts therefore give a limited registry-level account, not a complete safety comparison.
12. What the Result Does, and Does Not, Mean
The registry record describes a randomized crossover study designed to examine whether dialysate flow rate and membrane packing density relate to dialyzer performance. Its primary measure, KoA for urea, is a technical measure of urea-removal efficiency. The stated design and endpoint clarify what the investigators intended to assess, but the record does not report the numerical outcome estimates needed to characterize what the measurements showed.
Without mean values, contrasts, confidence intervals, or p-values, the direction, magnitude, and precision of any differences cannot be determined from the posted results. It is not possible to say from this record whether a particular dialyzer had higher or lower KoA, whether increasing flow rate changed KoA, or whether the relationship varied with packing density. The study summary describes the purpose of the measurements, not the findings.
The endpoint is also narrower than an overall assessment of patient benefit or harm. It concerns transfer performance during clinical hemodialysis, rather than a clinical outcome. No conclusion about a treatment’s clinical effectiveness should be drawn from the endpoint description alone. Likewise, the reported adverse-event entries are limited counts, with deaths not reported, and do not resolve broader safety questions.
The study enrolled 12 participants and used a crossover design, but the record does not report the number with complete measurements, the analysis population, or how repeated observations were handled. Those details matter when judging how much weight to give any statistical comparison. The registry record supports understanding the study question and measurement plan; it does not supply enough outcome or analysis information to judge the estimated device-performance differences.
13. Why This Trial Matters Statistically
This trial is statistically interesting because it uses a crossover design to study device performance across several conditions. In general, within-participant comparisons can reduce the influence of stable differences between people, since the same participant can contribute measurements under different conditions. That potential advantage depends on appropriate analysis of repeated observations and on accounting for period or order effects. The registry record does not report how these issues were handled.
The study also asks about an interaction in a practical statistical sense: whether the relationship between flow rate and performance depends on dialyzer membrane packing density. When an effect may vary across device types, an overall average can conceal different patterns. A clear analysis would need to define the contrasts that address this question and provide estimates with uncertainty. Those results and analysis details are not reported in the registry record.
Its endpoint is a continuous measure of device performance, and the record names the mean and standard error as summaries. This underscores the distinction between describing a measure and estimating a comparison. For interpretation, the contrast and its uncertainty are essential; a definition of KoA or a schedule of measurements cannot show whether the observed differences were substantial or precise.
The entry also illustrates the importance of complete registry reporting. The design and endpoint are described, but the primary numerical results, analysis methods, missing-data information, and sample-size rationale are not reported. Without them, a reader cannot reproduce or evaluate the intended statistical inference. The value of this record is therefore in identifying the question and design, while its statistical conclusions remain indeterminate from the posted 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 most immediate limitation for interpretation is that numerical results for the primary endpoint are not reported in the registry record. There are no means, standard errors, confidence intervals, or comparison tests available in the entry. The primary outcome is therefore defined but cannot be quantified from the posted information.
The record does not specify the dialysate flow-rate values, the order of treatment conditions, or the sequence-generation and allocation-concealment procedures. Although the study is identified as randomized and crossover, those details are not reported in the registry record. Washout procedures and the handling of period or carryover effects are also not described.
There is some variation in device labels between the intervention list and arm descriptions. The intervention list names Polyflux HD-C4 Big, HD-C4 Small, Optiflux 160NR, and Optiflux 200NR; the arm descriptions use HD-C4 Big, HD-C4 Small, F160NR, and F200NR. The record does not explain the naming differences. This may complicate matching the planned arms to outcome results, particularly since outcome values are not reported.
The registry reports enrollment of 12 but not the number completing each treatment condition, the analysis population, missing measurements, or reasons for missingness. It also does not report the sample-size justification or statistical analysis plan. These limitations prevent assessment of completeness, precision, and whether the analysis reflected the crossover design. They are limitations of the registry information and do not establish that the underlying study lacked these procedures or data.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Comparative Effects Of Dialysate Flow Rate And Membrane Packing On The Performance Of Dialyzers Used For Hemodialysis — NCT00636077.
- Registry record last updated 2025-07-14; status last verified 2025-07.
- Results first posted 2011-07-01.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry record describes a completed randomized, unmasked crossover study of four hemodialyzers in 12 participants with chronic kidney disease or chronic renal disease. The study examined dialysate flow rate and membrane packing density in relation to molecule transfer during clinical hemodialysis. Its primary endpoint was mean KoA for urea, with standard error, measured during the third treatment with each dialyzer.
The record lists 6 outcome measures and no analyses. Numerical primary outcome results, confidence intervals, p-values, the statistical analysis plan, missing-data information, and a sample-size rationale are not reported in the registry record. Serious and other adverse-event counts are recorded as 0 in each group; deaths are not reported. The entry therefore identifies the study question and design but does not provide the results needed to evaluate the primary statistical comparison.