Using Intradialytic Blood Pressure Slopes to Guide Ultrafiltration: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Using Intradialytic Blood Pressure Slopes to Guide Ultrafiltration (NCT03303391), a randomized na study. The primary outcome is Change in Mean Ambulatory Systolic Blood Pressure.

2. Clinical Question

3. Trial Design

The registry describes an open-label randomized clinical trial with a parallel design, comparing intradialytic blood pressure slope-based ultrafiltration with Standard Care. Participants in Standard Care had fluid and dialysis management directed by their individual nephrologist. In the IBPS Group, ultrafiltration prescriptions followed a prespecified protocol based on monthly assessment of intradialytic blood pressure slopes measured over a two-week period. The record does not provide further procedural details about the protocol.

The study also included a cross-sectional component. Its stated purpose was to evaluate associations between intradialytic blood pressure slopes assessed over two-week periods and measurements of extracellular water relative to body weight obtained with multifrequency bioimpedance spectroscopy. The registry lists change in extracellular volume/body weight ratio as a secondary outcome, but does not post a result for it in the information available for this analysis.

The listed enrollment is 14. For the primary outcome, the reported group sizes are 9 for Standard Care and 3 for the IBPS Group. The record does not explain the relationship between the enrollment total and these outcome group counts. The study status is terminated, with primary completion listed as 2020-01-01. The reason for termination is not reported in the registry record.

The record does not report the randomization sequence method, allocation concealment, eligibility criteria in detail, or the planned recruitment target. It identifies no masking, which means the trial was open label, but does not describe whether outcome measurement or analysis was conducted by people unaware of assignment. The registry record also does not report a protocol-level account of follow-up procedures beyond the primary outcome timeframe.

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

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: Due to two withdrawals in the intervention group (never began the intervention) the comparison is with 9 vs 3

6. Primary Endpoint

The registry lists the primary outcome as Change in Mean Ambulatory Systolic Blood Pressure, measured over Baseline, 4 months.

The primary endpoint is change in mean ambulatory systolic blood pressure from study baseline to completion at 4 months, measured in mmHg. Ambulatory measurement assesses blood pressure outside a single clinic reading and is intended to represent pressure across the measurement period described by the study. The endpoint is expressed as a change from baseline, so a negative value denotes a lower follow-up mean than baseline under the usual direction of subtraction. The registry identifies the summary measure as a mean and the measure of spread as standard deviation.

The outcome is relevant to the trial question because ultrafiltration prescriptions were guided by intradialytic blood pressure slopes, while the primary endpoint assesses ambulatory systolic pressure over the study period. That relationship makes the endpoint a way to evaluate blood pressure change alongside the fluid-management strategy. It does not, by itself, measure extracellular volume or establish a mechanism for any observed change.

The posted group summaries are -0.9 mmHg for Standard Care, with a standard deviation of 12.0, and -21.3 mmHg for the IBPS Group, with a standard deviation of 6.7. The registry does not report a confidence interval or a formal between-group estimate for this endpoint. Therefore, the mean changes and standard deviations describe the posted groups, but do not show how precisely the difference between treatment assignments has been estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins by distinguishing descriptive summaries from comparative analyses. The registry reports a mean change and standard deviation for each arm. The mean summarizes the group’s average change, while the standard deviation describes how dispersed individual changes are around that group mean. Neither quantity alone provides the uncertainty around the difference between randomized groups. The record lists no analyses for the primary outcome, and no comparative estimate, confidence interval, or p-value is reported in the registry record.

What does the standard deviation describe?

In general, a standard deviation describes variation among observations within a group. It is not a confidence interval for the mean and does not directly quantify uncertainty in a treatment contrast. The posted standard deviations are 12.0 for Standard Care and 6.7 for the IBPS Group. Because the arm sizes are 9 and 3, respectively, the amount of information supporting each group summary differs. In general, a group estimate based on fewer observations is more vulnerable to the influence of individual values.

Why is a between-group estimate important?

Randomized trials are designed to compare outcomes across assigned groups. A direct analysis can estimate the contrast between groups and quantify uncertainty around that estimate. Comparing the two arm means by inspection is not a substitute for that analysis: it does not account for sampling variability or provide a confidence interval. No between-group analysis is reported in the registry record, so the precision of the randomized comparison cannot be assessed from the posted summaries.

In general, a confidence interval gives a range of estimates compatible with the data and the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, while the interval’s location helps describe which values are compatible with the data. No confidence interval is posted for this primary outcome. It would not be appropriate to infer one from the arm summaries without doing a separate calculation, and no recalculated comparative estimate is reported.

What does open-label mean for interpretation?

The trial is listed as having no masking, so it was open label. In general, awareness of assigned treatment can affect care decisions, participant behavior, and outcome assessment, depending on the outcome and trial procedures. The endpoint is ambulatory systolic blood pressure, but the registry record does not explain who collected or assessed it, whether measurement procedures were standardized across arms, or whether analysts were unaware of assignment. These points cannot be resolved from the posted record.

The record describes random allocation and a parallel model. In general, random allocation aims to make comparison groups similar with respect to measured and unmeasured characteristics, on average, but it does not guarantee balance in a small sample. Details of sequence generation, allocation concealment, stratification, or other randomization procedures are not reported in the registry record. No claim about the success of those procedures can therefore be made from the available description.

How should planning illustrations be understood?

In general, a sample-size calculation is a planning exercise based on assumptions about the effect to detect, variability, significance level, allocation, and statistical method. The registry’s planning assumptions describe two-sided significance level 0.05, equal allocation, and a normal approximation, with the target effect defined as a stated fraction of the observed effect. Such an illustration is not an observed trial result and is not observed power. It does not show that the completed trial had the planned size or that its results have a particular probability of being correct. The trial’s own sample-size justification is not reported in the registry record.

In general, observed power is not a substitute for reporting an estimated effect with a confidence interval. The present record does not provide a comparative analysis from which to assess precision. Planning illustrations based on an observed effect can be sensitive to that effect estimate, especially when the observed group sizes are small. They should be read only as conditional planning calculations under their stated assumptions, not as evidence that the trial was adequately powered or underpowered.

The primary outcome is a continuous measure summarized by a mean and standard deviation. The record does not report whether the analysis used an unadjusted comparison, baseline-adjusted model, repeated-measures model, or another method. It also does not report model assumptions, diagnostics, or any sensitivity analysis. Consequently, no particular inferential method or its assumptions should be attributed to the trial beyond the descriptive summaries and planning assumptions recorded.

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("Standard Care", "IBPS Group")
n   <- c(9, 3)
m   <- c(-0.9, -21.3)
sp  <- c(12, 6.7)
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  Standard Care  9  -0.900  12.000  -10.124  8.324
CARM  IBPS Group  3  -21.300  6.700  -37.944  -4.656

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome, change in mean ambulatory systolic blood pressure, and one secondary outcome, change in extracellular volume/body weight ratio. It also describes a cross-sectional component examining associations between intradialytic blood pressure slopes and extracellular water relative to body weight. The record does not report a statistical plan for controlling multiplicity across outcomes, time points, or analyses. It also does not report whether any outcomes or analyses were prespecified beyond the descriptions in the registry.

In general, testing multiple hypotheses can increase the chance of finding an apparently notable result by chance. A multiplicity strategy may define which comparisons are primary, allocate error rates, or use an adjustment procedure. No such approach is reported in the registry record. Because no inferential analyses are posted for the primary outcome, there is no reported set of p-values from which to assess multiplicity handling.

Missing-data methods are not reported in the registry record. The record does not state whether all randomized participants contributed primary outcome measurements, how missing measurements were handled, or whether any imputation or sensitivity analysis was used. The listed enrollment is 14, while the primary outcome groups contain 9 and 3 participants; the record does not explain the relationship between those counts. It is not possible to determine from these entries whether the difference reflects missing outcome data, a distinction in analysis populations, or another reason.

The record does not define an intention-to-treat, per-protocol, or other analysis population. It does not describe participant flow by assignment, exclusions from analysis, withdrawals, or adherence to the ultrafiltration protocol. These omissions make it difficult to assess how the outcome summaries relate to the randomized population. No assumptions about missing outcomes or analysis membership should be inferred from the arm summaries alone.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The safety figures list no serious adverse events in either group: 0 among 9 at risk in Standard Care and 0 among 3 at risk in the IBPS Group. Deaths are also listed as 0 in each group. The registry lists other adverse events affecting 5 of 9 at risk in Standard Care and 3 of 3 at risk in the IBPS Group. These are the counts recorded for the groups; the record does not provide further detail about the nature, timing, severity, or relatedness of the other adverse events.

In general, zero recorded serious events in a small group does not establish that an event cannot occur, and the absence of a recorded event is not proof of no risk. The arm sizes are unequal, with only 3 participants reported at risk in the IBPS Group, so the safety counts should be read in light of the limited number of participants. The registry does not report an inferential comparison of adverse events. The counts do not establish a comparative safety difference, and they do not support a general safety conclusion beyond the events recorded for these participants.

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

The posted primary outcome data describe mean changes in ambulatory systolic blood pressure for two randomized groups: -0.9 mmHg for Standard Care and -21.3 mmHg for the IBPS Group. The associated standard deviations are 12.0 and 6.7. These summaries tell readers what was reported for each group, but they do not provide the direct between-group estimate or its precision. The trial record reports no primary outcome analysis, confidence interval, or p-value.

The small and unequal outcome group sizes are important context. The registry reports 9 participants in Standard Care and 3 in the IBPS Group, while enrollment is listed as 14. The reason for the difference between those figures is not reported in the registry record. With few observations in the outcome groups, the summaries can be sensitive to individual results, and the record does not provide individual data to assess that sensitivity.

The findings do not establish that slope-guided ultrafiltration caused the reported change, nor do they establish that the groups were equivalent. The descriptive changes are not a substitute for a randomized between-group estimate with uncertainty. The registry also does not report the reason for termination, the trial’s sample-size justification, or the handling of missing outcomes. These uncertainties limit conclusions about the study’s completeness and inferential strength.

The study’s secondary outcome concerns change in extracellular volume/body weight ratio, and its cross-sectional component concerns associations involving intradialytic blood pressure slopes and bioimpedance measurements. Results for those analyses are not reported in the registry record. The primary outcome summaries cannot be used as evidence about those separate questions.

In general, a registry result is most informative when read together with the analysis method, participant flow, and uncertainty around the estimated contrast. Those details are not reported for this primary outcome. The available figures support a descriptive account of the reported arm summaries, not a definitive claim about the comparative effect or broader implications of the intervention.

14. Why This Trial Matters Statistically

This trial raises a useful statistical question: whether measurements made during dialysis can guide ultrafiltration prescriptions and be evaluated against a patient-level blood pressure outcome. The registry describes both a randomized comparison and a cross-sectional component relating intradialytic blood pressure slopes to bioimpedance measurements. These are distinct designs and questions: the randomized component compares assigned management strategies, while the cross-sectional component evaluates associations.

The posted results also illustrate why group summaries need to be read alongside sample sizes and uncertainty. The primary outcome means differ descriptively, but the reported outcome groups are unequal, with 9 participants in Standard Care and 3 in the IBPS Group. No comparative estimate or confidence interval is reported. Without those elements, a reader cannot judge how precisely the randomized contrast was estimated or distinguish a potentially stable pattern from one that could be strongly influenced by a small number of observations.

The trial is marked terminated, and enrollment is listed as 14. The registry does not report the reason for termination or explain the relationship between enrollment and the primary outcome counts. Those omissions matter statistically because participant flow and analysis populations help establish what data contribute to an estimate and how broadly it should be interpreted.

More generally, the record shows the difference between a planning illustration and an analysis of observed trial outcomes. Sample-size planning depends on assumptions, while the interpretation of trial findings depends on the actual comparative estimate and its uncertainty. The record’s planning assumptions do not replace an outcome analysis, and no trial-specific sample-size justification is reported. This makes the study a clear example of why descriptive results, planning calculations, and inferential conclusions should be kept separate.

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 registry record has several limitations for interpreting this trial. Although it lists randomized allocation and a parallel design, it does not report the random-sequence method or allocation concealment. The study is open label, and the record does not explain who measured the primary outcome or whether outcome assessment and analysis were masked. Detailed eligibility criteria and the full intervention protocol are also not reported.

The primary outcome arm counts are 9 for Standard Care and 3 for the IBPS Group, while enrollment is listed as 14. The registry record does not reconcile these figures or explain which participants contributed to the outcome summaries. Participant flow, withdrawals, exclusions, adherence, and the analysis population are not reported. Missing-data methods and sensitivity analyses are not reported either.

The registry posts group means and standard deviations but no inferential analysis, comparative estimate, confidence interval, or p-value for the primary outcome. It does not describe the statistical model, adjustment for baseline measurements, assumptions, or diagnostic checks. The trial’s own sample-size justification and any interim analyses are not reported in the registry record. The reason for the terminated status is also not reported.

The registry lists a secondary outcome and describes a cross-sectional component, but does not report results for those analyses. It also does not report a multiplicity strategy. Safety entries include counts of serious and other adverse events, but detailed event descriptions, severity, timing, and relatedness are not reported. Together, these omissions restrict the available interpretation to the posted descriptive summaries and event counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Using Intradialytic Blood Pressure Slopes to Guide Ultrafiltration — NCT03303391.
• Registry record last updated 2022-08-25; status last verified 2022-03.
• Results first posted 2022-08-25.
• 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

NCT03303391 is a randomized, open-label, parallel clinical trial comparing intradialytic blood pressure slope-based ultrafiltration with Standard Care in hemodialysis patients. The study also included a cross-sectional component concerning blood pressure slopes and bioimpedance measurements. The registry lists enrollment of 14 and status as terminated.

The primary outcome was change in mean ambulatory systolic blood pressure from baseline to 4 months. The posted mean changes are -0.9 mmHg for Standard Care and -21.3 mmHg for the IBPS Group, with standard deviations of 12.0 and 6.7, respectively. The outcome group sizes are 9 and 3. No comparative analysis or confidence interval is reported in the registry record. The reason for termination, the relationship between enrollment and outcome counts, and results for the listed secondary outcome are not reported.