Electrical Impedance Myography as an Outcome Measure in Amyotrophic Lateral Sclerosis Clinical Trials: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Electrical Impedance Myography as an Outcome Measure in Amyotrophic Lateral Sclerosis Clinical Trials (NCT00620698), a registered phase not stated study. The primary outcome is Electrical Impedance Myography.

2. Clinical Question

The aim described in the registry is to assess outcome measures, not to estimate the effect of a treatment. The brief summary frames this as a way to judge whether EIM can track disease progression and could be useful in future ALS trials. The central statistical issue is therefore measurement performance: how much participant-to-participant variability there is in the measured rate of decline relative to the group mean. No numerical result for that comparison is reported in the registry record, so the relative performance of the measures cannot be determined from the record.

3. Trial Design

This is a completed study of outcome measurement in ALS, registered as NCT00620698. The registry lists Beth Israel Deaconess Medical Center as sponsor, a start date of 2007-05, a primary completion date of 2011-03, and enrollment of 89. The brief summary describes a plan involving multiple institutions and approximately 120 ALS patients followed for one year. The registry’s enrollment figure and the brief’s planned approximate enrollment are both stated in the record; the reason for the difference is not reported in the registry record.

The study evaluates EIM alongside ALSFRS-R and handheld dynamometry. The primary outcome is titled Electrical Impedance Myography and has a six-month timeframe. The brief describes comparing outcome measures to assess their ability to detect progression. The registry lists one arm, ALS patients, and does not describe an assigned treatment or a control arm. Allocation is not stated, and this is not a randomized comparison. The arms therefore should not be read as like-for-like treatment groups.

The brief describes one-year follow-up, while the primary outcome’s listed timeframe is six months. The registry does not explain the relationship between those timeframes or report the schedule of individual assessments. The planned sample-size justification, detailed statistical analysis plan, and reasons for the final enrollment figure are not reported in the registry record. The record indicates that the study is completed, but that status alone does not supply the missing endpoint estimates or analysis details.

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.

6. Primary Endpoint

The registry lists the primary outcome as Electrical Impedance Myography, measured over 6 months.

The primary endpoint is the coefficient of variation (CoV) in the rate of decline for EIM over the listed six-month timeframe. The registry defines this as the standard deviation of the rate of decline across the group divided by the group’s mean rate of decline. The same approach is described for ALSFRS-R and handheld dynamometry, allowing the variability of each measure’s rate of decline to be considered relative to its mean rate.

In general, a coefficient of variation expresses variability relative to a measure’s mean, rather than describing variability on the measure’s original scale alone. The registry’s rationale is that a lower CoV suggests more homogeneous rates of decline relative to the average decline and may indicate greater sensitivity to a potential treatment effect. In that reasoning, a measure with less relative variation and a larger mean decline could require fewer participants in a future trial. This is a rationale for evaluating the measure, not evidence that EIM improves health outcomes or changes ALS progression.

The registry lists a 95% confidence interval as the dispersion type but does not report a numerical interval or numerical CoV estimate. The endpoint’s numerical result is not reported in the registry record, so its precision and its comparison with the other measures cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the coefficient of variation describe?

The registry defines the CoV for each outcome measure as the standard deviation in the rate of decline across the group divided by the mean rate of decline. This puts the spread of the observed decline rates in relation to their average. It is a relative measure: it does not describe the spread on the original scale by itself. The record applies this calculation to EIM, ALSFRS-R, and handheld dynamometry.

As general statistical context, a mean describes the center of a set of measurements, while a standard deviation describes how dispersed those measurements are around that center. Dividing the standard deviation by the mean expresses dispersion relative to the average. The CoV can help compare relative variability across measures whose raw units differ, but it does not by itself show whether a measure is clinically meaningful, whether it accurately reflects disease progression, or whether a treatment changes outcomes.

Why is a lower value considered useful?

The registry’s rationale is that a lower CoV in the rate of decline indicates greater homogeneity relative to the mean rate of decline. If participant trajectories are less variable relative to the average decline, a future study may be better able to distinguish a treatment-related change from variation among participants. The description also links a lower CoV to a smaller standard deviation and a larger mean rate of decline. This is the stated measurement rationale; it is not a reported finding for this study because the numerical CoV estimates are absent.

As general statistical context, an outcome measure’s usefulness depends on more than relative variability. The meaning of the measure, the pattern of change over time, the quality of measurement, and the way missing observations are handled can all matter. The registry record does not provide enough analysis detail to assess those features for this study.

What does the confidence interval add?

A confidence interval communicates uncertainty around an estimated quantity. In general, a narrower interval indicates greater precision under the analysis method used, while a wider interval indicates more uncertainty. The registry names a 95% confidence interval as the dispersion type for the primary outcome, but it does not report the interval endpoints or the estimate to which they apply. It is therefore not possible to assess the precision of the primary result or whether estimates for the different outcome measures overlap.

The interval is also distinct from the CoV itself. The CoV is the endpoint quantity described in the record; a confidence interval would express uncertainty around an estimate of that quantity. Without the estimate and interval values, neither the magnitude of relative variability nor the uncertainty around it can be evaluated.

How should the planning calculations be read?

The sample-size illustrations are described as planning calculations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are assumptions for illustrations, not a description of the study’s design. The registry does not report the numerical observed effect or the numerical participant requirements in those illustrations.

As general statistical context, a planning calculation asks how many participants might be needed under specified assumptions to detect a chosen effect with a specified probability of detection. Such an illustration depends on the assumed effect size, variability, allocation, significance level, and analysis approach. It is not observed power: it does not describe the probability that the completed study detected an effect based on its results. Nor does it establish that the study itself was planned using those assumptions. The registry does not report the original sample-size justification or a full statistical analysis plan.

What can the record establish?

The record identifies the endpoint, its stated calculation, the measures intended for comparison, and the study’s enrollment and status. It does not report the numerical primary result, confidence interval limits, or measure-to-measure comparison estimates. A statistical interpretation must therefore remain focused on the endpoint’s purpose and cannot rank the measures or quantify their performance from the posted results.

10. Multiplicity, Missing Data and Analysis Populations

The study description identifies three measures: EIM, ALSFRS-R, and handheld dynamometry. EIM is listed as the primary outcome, while ALS Functional Rating Scale and Handheld Dynamometry are listed as secondary outcomes. The registry also indicates three outcome measures and zero analyses. The number of analyses does not provide results or explain how the planned comparisons were handled.

When a study assesses multiple outcomes or makes multiple comparisons, multiplicity can increase the chance of finding an apparently notable result by chance. As general statistical context, researchers may address this through a prespecified hierarchy, an adjustment to significance thresholds, or other methods. Whether any such approach was planned or used is not reported in the registry record. No multiplicity adjustment or testing hierarchy is reported, and no numerical comparison results are available to evaluate.

Missing-data methods are not reported in the registry record. The record does not state how incomplete follow-up, unavailable measurements, or participants without a usable rate of decline were handled. The analysis population is also not described beyond the listed ALS patient arm and enrollment figure. It is not reported whether all enrolled participants contributed to each measure-specific analysis or how the analysis set was defined.

These omissions matter because variability estimates can depend on which observations contribute to the calculation and how incomplete measurements are treated. Without information about missingness and analysis populations, the reported endpoint definition alone is not enough to assess potential bias or reproduce the analysis.

11. 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.

The registry lists 89 participants at risk for both serious adverse events and other adverse events, with 0 affected in each category. These are the posted counts for the listed ALS patient group. They should be read as registry-reported event figures, not as a detailed account of every safety observation or as a comparison between treatment groups. The study is not described as a randomized treatment comparison.

The registry does not list serious adverse event terms. Deaths are recorded as null, which means a death count is not reported in the registry record; it should not be read as a reported count of zero. The record also does not report the safety observation period, definitions used for event reporting, or further detail about how adverse events were collected. The figures therefore give a limited account of what is entered in the registry and do not establish the absence of all safety events.

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

The study addresses a statistical question about measurement: how consistently different measures capture the rate of ALS progression across participants. The registry’s stated endpoint uses the CoV of decline rates to express variation relative to the mean. That approach provides a rationale for evaluating whether EIM could be useful as an outcome measure in future trials.

The posted record does not provide numerical CoV estimates, confidence interval limits, or comparative results for EIM, ALSFRS-R, and handheld dynamometry. It therefore cannot show which measure had the lowest relative variability, how precise any estimate was, or whether differences among measures were substantial. The study’s completed status does not fill in those missing results.

The record also does not test a treatment against a control group. It should not be interpreted as showing that EIM or any other measure changes disease progression, or that a treatment works or does not work. The description presents EIM as a candidate outcome measure, with the intended purpose of helping assess potential treatment effects in later trials.

Likewise, planning illustrations based on an observed effect are not trial outcomes and are not observed power. They describe hypothetical sample-size requirements under stated assumptions. Because the effect and numerical illustrations are not reported in the registry record, they do not establish how many participants a future study would need.

The justified conclusion is narrow: the registry documents an evaluation of outcome measures and defines the primary endpoint, but does not report enough numerical analysis to judge the measures’ comparative performance.

13. Why This Trial Matters Statistically

Outcome measures shape what a clinical trial can detect. A measure with a clear signal and relatively low variation may make it easier for a trial to distinguish a treatment-related change from variation in participants’ measurements. The registry’s focus on the CoV of the rate of decline reflects this statistical concern: it relates variability across participants to the mean rate of decline rather than considering variability alone.

Comparing EIM with ALSFRS-R and handheld dynamometry is relevant to the stated goal of assessing different ways to track ALS progression. The brief summary explains the intended longer-term value: an effective outcome measure could support faster trials requiring fewer participants. That is the rationale for studying measurement performance, not a result established by this registry record.

The record is also a useful example of the distinction between an endpoint definition and an endpoint finding. It explains what the CoV is intended to capture and why a lower value may be desirable, but it does not report the numerical estimates needed to evaluate that rationale in this study. Without those results, readers cannot compare the measures or judge their precision from the posted record.

For statisticians and clinical researchers, this distinction matters when translating a measurement study into future trial planning. A proposed advantage in relative variability can motivate further evaluation, but planning requires the observed estimates and their uncertainty, along with details of the analysis and missing-data handling. Those details are not reported in the registry record.

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 registry defines the primary endpoint but does not report its numerical estimate or confidence interval. It also does not report comparable numerical results for ALSFRS-R or handheld dynamometry. As a result, the stated aim of comparing measurement performance cannot be evaluated quantitatively from the posted record.

The record does not describe the statistical analysis plan, the method used to estimate individual rates of decline, or the procedure used to calculate uncertainty. It does not report how repeated measurements were scheduled or analyzed, or how missing observations were handled. The analysis population for each outcome is not described. These details could affect both the estimated CoV and its precision.

The registry lists 89 enrolled participants, while the brief summary describes a plan for approximately 120. The reason for this difference is not reported in the registry record. The brief describes one-year follow-up, whereas the primary outcome timeframe is six months; the relationship between these timeframes is not explained. Allocation is not stated, and the record does not describe a like-for-like control comparison.

The record indicates three outcome measures and zero analyses, but does not describe a multiplicity approach or provide results for the secondary outcomes. The safety entry also gives limited context: serious and other event counts are listed, but event terms and the observation period are not reported; deaths are null rather than a reported zero count.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Electrical Impedance Myography as an Outcome Measure in Amyotrophic Lateral Sclerosis Clinical Trials — NCT00620698.
• Registry record last updated 2014-09-25; status last verified 2014-09.
• Results first posted 2014-09-10.
• 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.

18. Record Summary

NCT00620698 is a completed study of EIM as an outcome measure in ALS clinical trials, sponsored by Beth Israel Deaconess Medical Center. The registry lists enrollment of 89 and dates of 2007-05 to 2011-03. The brief describes a plan for approximately 120 ALS patients followed for one year, while the primary outcome timeframe is six months; the reason for the enrollment difference and the relationship between the timeframes are not reported in the registry record.

The primary endpoint is the CoV in the rate of decline for EIM, with ALSFRS-R and handheld dynamometry also described as measures for comparison. The record explains the endpoint’s rationale but does not report numerical estimates or confidence interval limits. It describes no randomized treatment comparison, and allocation is not stated. Serious and other adverse event counts are listed as 0 affected among 89 at risk; deaths are not reported.