Handgrip Exercise for Arteriovenous Fistula Maturation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Handgrip Exercise for Arteriovenous Fistula Maturation (NCT01061008), a randomized na study. The primary outcome is Venous Diameter..

2. Clinical Question

3. Trial Design

The registry describes a completed, randomized, single-masked, parallel-group study sponsored by Bangor University. The listed study start is 2008-01, and the primary completion date is 2012-01. The phase is recorded as NA. Enrollment is listed as 31. These details describe the registered study, but do not establish how many participants completed follow-up or were included in each analysis.

Participants were assigned to postoperative progressive handgrip exercise or treatment as usual. The exercise arm description specifies an eight week training program. No description of usual care appears in the arm information. The registry identifies the study as single-masked, but does not report who was masked or how masking was maintained. The randomization method, allocation concealment procedures, and whether the groups were balanced on baseline characteristics are not reported in the registry record.

The primary outcome was venous diameter at 3 months, measured by duplex ultrasonography. Posted group results include 10 participants in the handgrip exercise arm and 9 in the treatment-as-usual arm. The record does not explain the relationship between those outcome counts and the enrollment of 31. It also does not report whether all randomized participants were followed, why some participants may not have contributed outcome data, or which analysis population was intended.

Three secondary outcomes are listed: maximum handgrip strength, handgrip endurance, and forearm muscle cross-sectional area. The registry lists four outcome measures overall, but reports no analyses. Details of the protocol, sample-size justification, planned analysis methods, and any interim analyses are not reported in the registry record. The design information supports a description of the intended comparison, while the absence of those details limits evaluation of how the reported results relate to the original analysis 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

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Venous Diameter., measured over 3 months.

The primary endpoint is venous diameter, a continuous measurement reported in millimeters at 3 months. The registry says measurements were made by duplex ultrasonography at locations 5 to 10 cm proximal to the anastomosis. The exact location depended on wound dressings and turbulent flow around the anastomosis. Scanning positions were traced using transparent sheets to support analogous measurement locations across scans. Diameters were measured from the inner edges of the vascular wall using conventional grey-scale B-mode imaging.

In general, a vessel diameter is a structural measure of vessel size. It can be used to assess a physical aspect of fistula development, and the registry’s study question links the outcome to fistula maturation. A diameter measurement is not, by itself, a complete assessment of maturation, function, or clinical usability. Other clinical and functional considerations may matter, but their definitions and assessment are not reported in the registry record.

The posted results give a mean and standard deviation for each arm. At 3 months, the handgrip exercise arm had a mean of 5.78 mm and standard deviation of 0.51; the treatment-as-usual arm had a mean of 6.42 mm and standard deviation of 0.89. No confidence interval or inferential test for the between-arm comparison is reported. These summaries describe the observed measurements, but do not quantify uncertainty around the group contrast.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is a continuous measurement, and the registry summarizes it using the mean and standard deviation. These summaries answer different descriptive questions. The mean locates the center of the observed values, while the standard deviation describes how dispersed individual measurements are around that center. Neither summary alone gives the uncertainty of a treatment-group comparison.

What does a confidence interval add?

In general, a confidence interval gives a range of values compatible with the data under a specified statistical method. For a comparison between groups, it communicates both the estimated direction and the precision of the estimated effect. A narrow interval indicates greater precision than a wide interval, while an interval that includes values on both sides of no difference can indicate that the data do not distinguish those possibilities clearly. The registry does not report a confidence interval for the venous-diameter comparison.

A p-value, when reported, addresses how compatible the observed data are with a stated null model, given the test assumptions. It does not measure the probability that the null hypothesis is true, nor does it describe the size or clinical importance of an effect. No p-value or test result for the primary comparison is reported in the registry record. Consequently, the posted arm means should not be converted into an unsupported claim of statistical significance or lack of significance.

Why does the comparison method matter?

General statistical practice distinguishes a comparison of group means from separate descriptions of each group. A between-group analysis must account for the variability of the measurements and the number of observations contributing to each arm. Depending on the prespecified plan and available data, an analysis might also account for baseline measurements or other design features. The registry does not report whether there was a baseline diameter measurement, whether adjustment was planned, which statistical test was used, or whether assumptions were assessed. No specific analysis can therefore be attributed to the trial from this record.

For continuous outcomes, standard methods often rely on assumptions about the distribution and independence of observations. In general, marked skewness, influential extreme values, or dependence among observations can affect the reliability of a simple comparison. No distributional diagnostics, participant-level data, or alternative analysis are reported. The standard deviations alone do not show whether these assumptions were satisfied.

How should the participant counts be read?

The registry gives endpoint counts of 10 for handgrip exercise and 9 for treatment as usual. These counts indicate how many observations are included in the posted summaries, but the record does not explain whether they are the numbers randomized, the numbers measured at 3 months, or a subset selected for analysis. Enrollment is listed as 31, and the relationship between enrollment and endpoint counts is not described. There is no reported participant flow, reason for missing measurements, or analysis-population definition. These gaps make it difficult to assess whether the observed summaries represent all randomized participants or only those with recorded endpoint values.

In general, missing outcome data can reduce precision and can introduce bias if missingness is related to the outcome or differs between assigned groups. The potential direction and size of any such effect cannot be determined without the reasons for missingness and appropriate analyses. No imputation method, sensitivity analysis, or missing-data assumption is reported in the registry record.

What do planning illustrations mean?

In general, a sample-size calculation describes how many participants might be needed under specified assumptions about an effect, variability, significance level, power, allocation, and analysis method. The registry’s planning assumptions describe an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is expressed as a fraction of the observed effect. Such illustrations are planning scenarios, not observed trial outcomes and not observed power. They do not establish that the trial was designed with those assumptions, and the registry does not report its own sample-size justification. No specific planning results are stated in the registry record.

The registry records zero analyses. That absence is consequential: there is no posted inferential estimate for the primary endpoint from which to judge the size and precision of the group contrast. Any simple recalculation from arm-level means and standard deviations would be an unadjusted analysis based on summary statistics, not a replacement for the sponsor’s planned analysis. Since no sponsor analysis is posted, the available record supports descriptive interpretation only. In general, an analysis reported by the trial sponsor would take precedence over such a recalculation if a discrepancy were identified.

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("Handgrip Exercise", "Treatment as Usual")
n   <- c(10, 9)
m   <- c(5.78, 6.42)
sp  <- c(0.51, 0.89)
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  Handgrip Exercise  10  5.780  0.510  5.415  6.145
CARM  Treatment as Usual  9  6.420  0.890  5.736  7.104

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three secondary outcomes: maximum handgrip strength, handgrip endurance, and forearm muscle cross-sectional area. It also lists four outcome measures overall. Only the primary venous-diameter outcome has numerical results in the posted information. The other outcome results, their time points, and any associated estimates or uncertainty are not reported in the registry record.

Multiplicity arises when several outcomes or several statistical tests are examined. In general, conducting many tests can increase the chance of finding an apparently unusual result by chance, so a prespecified analysis plan may define a primary outcome and explain how secondary comparisons will be interpreted or adjusted. The registry does not report a multiplicity strategy, a hierarchy among outcomes, or whether any adjustment was used. With no analyses posted, it is not possible to assess how multiple outcomes were handled.

Missing data reporting is also limited. The primary endpoint summaries include 10 participants in the exercise arm and 9 in the treatment-as-usual arm, while enrollment is listed as 31. The registry does not provide participant flow, reasons for missing measurements, or a definition of the analysis population. It does not report an intention-to-treat analysis, a per-protocol analysis, imputation, or sensitivity analyses. It is therefore unclear how participants without posted endpoint measurements were treated.

These omissions do not prove that analyses or procedures were absent from the conduct of the trial. They mean that the registry record does not describe them. Without outcome reporting and missing-data methods, readers cannot assess the completeness of the outcome evidence or the robustness of the descriptive summaries to alternative assumptions.

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 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports no serious adverse events among the 10 participants at risk in the handgrip exercise arm and no serious adverse events among the 9 participants at risk in the treatment-as-usual arm. The record lists 2 other adverse events among 10 participants at risk in the handgrip exercise arm and 0 among 9 at risk in the treatment-as-usual arm. These are posted counts for the groups and categories named in the registry; they do not establish that the intervention caused or prevented an event.

The number of participants at risk is small, so the observed counts provide limited information about the range of possible event frequencies. In general, observing no events in a group does not establish that the underlying risk is zero. The registry does not provide event descriptions for the other adverse events, severity details for those events, or information about their timing, duration, or relationship to the intervention. The deaths field has no reported values, so deaths are not reported in the registry record; they should not be interpreted as zero.

These adverse-event entries should be read as registry-reported counts, not as a complete safety assessment. The record does not report a formal comparison of adverse events between the groups or explain how events were monitored and classified.

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

The posted primary results show the observed venous-diameter summaries at 3 months: 5.78 mm (standard deviation 0.51) for handgrip exercise and 6.42 mm (standard deviation 0.89) for treatment as usual. These values describe the participants included in the arm-specific summaries. The registry does not report an estimated between-group effect, confidence interval, or p-value, so the precision and statistical evidence for a group contrast cannot be assessed from these results.

The results do not establish that the exercise program changed fistula maturation. Venous diameter is a structural measure, and the registry does not provide a definition of successful maturation or a broader functional outcome. A mean diameter alone cannot indicate whether a fistula was usable or whether other clinically relevant aspects of maturation were met. Such outcomes are not reported in the registry record.

The registry’s randomized designation describes the intended trial design, but important implementation details are absent, including the randomization method, masking roles, and analysis plan. The number of endpoint observations is also smaller than the listed enrollment, and the record does not explain the difference. These reporting gaps limit conclusions about representativeness, potential bias, and the completeness of follow-up.

The available information does support a narrow descriptive statement: the record contains arm-specific mean and standard deviation values for venous diameter at 3 months, along with endpoint counts and limited adverse-event counts. It does not support a definitive claim about the direction, size, or precision of a treatment effect. The absence of a reported analysis should not be confused with evidence of no effect, just as a numerical difference between sample means should not be taken as proof of an effect.

14. Why This Trial Matters Statistically

This trial illustrates why a registered study’s design and its posted results need to be read together. The registry describes random allocation to an eight week postoperative handgrip exercise program or treatment as usual, with venous diameter as the primary endpoint at 3 months. It also supplies group-level means and standard deviations, which can be useful descriptive information. But the record lists no analyses, so the core inferential quantities for the primary comparison are absent.

In general, estimates of effect and measures of uncertainty are central to interpretation. Means show the location of observed measurements, while standard deviations show participant-level variability. Neither tells readers how precisely the groups differ. Without an estimated contrast and confidence interval, readers cannot judge the range of effects compatible with the data. A p-value, if available, would answer a different and narrower question; it would not substitute for an effect estimate and its precision.

The listed enrollment and endpoint counts also highlight the importance of participant flow. Enrollment is 31, while the two primary outcome summaries include 10 and 9 participants. Without an explanation of who was measured, who was analyzed, and why other participants do not appear in the summaries, it is difficult to assess the impact of missing outcomes. This issue is especially relevant in small studies, where each observation can have substantial influence on a group summary.

The entry also demonstrates that registering secondary outcomes is not the same as reporting their results. Handgrip strength, endurance, and forearm muscle cross-sectional area are listed, but numerical findings and multiplicity procedures are absent. Taken together, these features make the record useful for describing the trial question and its reported measurements, while also showing why transparent analysis and complete outcome reporting are needed for stronger statistical interpretation.

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.

Several limitations arise from the information available in the registry record. Although the trial is described as randomized and single-masked, the method of randomization, allocation concealment, and identity of the masked party are not reported. Without these details, readers cannot fully assess how allocation was implemented or whether masking could have influenced measurement or care.

The intervention is described as an eight week postoperative progressive handgrip exercise program, but the exercise prescription, progression rules, monitoring, and adherence are not reported. Treatment as usual has no arm description. The contrast between the groups is therefore not fully characterized, and it is unclear what care the comparator group received.

The primary outcome description includes ultrasound measurement procedures and the use of traced scanning positions, but the registry does not report assessor masking, measurement reliability, or whether the same personnel performed each assessment. The location varied within the stated range depending on dressings and turbulent flow around the anastomosis. The record does not provide information about how any resulting variation was handled analytically.

The endpoint counts are 10 and 9, while enrollment is 31. Participant flow and reasons for absent endpoint values are not reported. No analysis population, missing-data strategy, confidence interval, p-value, or sponsor analysis is posted. These omissions limit assessment of precision, bias, and robustness. The listed secondary outcomes have no posted numerical results, and multiplicity handling is not reported. Finally, the primary endpoint is a diameter measurement; broader definitions or outcomes for fistula maturation are not reported in the registry record. These are limitations of the registered information and do not establish what was or was not done outside the record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Handgrip Exercise for Arteriovenous Fistula Maturation — NCT01061008.
• Registry record last updated 2014-07-15; status last verified 2014-06.
• Results first posted 2014-07-15.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry record describes NCT01061008, titled “Handgrip Exercise for Arteriovenous Fistula Maturation.” It lists a completed randomized, single-masked, parallel-group study sponsored by Bangor University, with enrollment of 31 and phase recorded as NA. The listed study start is 2008-01, and primary completion is 2012-01.

The comparison was postoperative progressive handgrip exercise, described as an eight week program, versus treatment as usual in people with chronic kidney disease. The primary outcome was venous diameter in millimeters at 3 months, measured by duplex ultrasonography. The posted arm summaries are 5.78 mm (standard deviation 0.51; 10 participants) for handgrip exercise and 6.42 mm (standard deviation 0.89; 9 participants) for treatment as usual.

Three secondary outcomes are listed, but their numerical results are not reported. The registry reports no analyses or inferential comparison for the primary endpoint. Serious adverse event counts are 0 in each arm; other adverse event counts are 2 in the exercise arm and 0 in the treatment-as-usual arm. Deaths are not reported in the registry record.