Effect of Noninvasive Ventilation on Lung Function in Amyotrophic Lateral Sclerosis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Noninvasive Ventilation on Lung Function in Amyotrophic Lateral Sclerosis (NCT00537446), a randomized na study. The primary outcome is Difference in Pulmonary Function and Respiratory Muscle Pressure Testing.

2. Clinical Question

The registry describes an acute physiological question, rather than a question about long-term preservation of breathing function. Its study summary explains that noninvasive ventilation is used as breathing assistance in ALS, while the acute effect on breathing muscle function was uncertain. The proposed comparison was intended to examine measurable changes in respiratory testing under different pressure levels.

The record does not establish what effect was observed. It states that measurements were collected, but were not analyzed as specified in the primary outcome description because the sample size was considered insufficient to generate enough statistical significance. The principal investigator no longer had the raw data on file, and efforts to retrieve it were unsuccessful. Consequently, the clinical question is identifiable from the design, but the registry record does not report an analyzed estimate answering it.

3. Trial Design

The study was randomized and used a crossover model. The two listed conditions were high-level and low-level noninvasive positive pressure ventilation. Each subject was scheduled to receive 2 hours of high-level ventilation and 2 hours of low-level ventilation. In a crossover design, the same participant receives each study condition, allowing comparisons within participants rather than relying only on comparisons between separate groups.

The registry lists masking as single, but does not report who was masked or how masking was maintained. It also does not report the sequence assigned to each participant, whether the order was balanced, or whether a washout period separated conditions. Those details matter because order, carryover, and awareness of treatment can influence measurements in a crossover study. They cannot be inferred from the model label alone.

Enrollment was 8, and the study status is recorded as terminated. The start date is 2007-09 and the primary completion date is 2012-08. Columbia University is listed as the sponsor. The phase is recorded as NA. The registry identifies 3 outcome measures and 0 analyses. The primary outcome description says data were collected but not analyzed as specified, and that the raw data could not be recovered.

The randomized crossover structure could have supported a comparison of acute measurements under the two ventilation levels if the planned data and analysis were available. However, the record does not report the participant-level measurements, a treatment-effect estimate, or an inferential analysis. It therefore documents the intended design and the failure to produce the specified primary analysis, not a completed estimate of the contrast.

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: Data were collected but not analyzed as specified in the title because the sample size does not generate enough statistical significance. PI no longer has raw data on file. All efforts have been made to retrieve the data and data could not be recovered.

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 Difference in Pulmonary Function and Respiratory Muscle Pressure Testing, measured over 5 hours.

The primary endpoint is titled “Difference in Pulmonary Function and Respiratory Muscle Pressure Testing.” It is intended to measure respiratory physiology, including pulmonary function and respiratory muscle pressure, after exposure to the ventilation conditions. The registry specifies a timeframe of 5 hours but gives no further endpoint definition, unit, summary parameter, or measure of dispersion. It does not identify particular tests, the exact measurement schedule, or the rule for combining measurements into a primary value.

These measures are relevant to the study’s stated acute question because they assess breathing function and respiratory muscle pressure rather than relying on a longer-term clinical outcome. A within-participant comparison could, in principle, examine whether measurements vary between high-level and low-level ventilation and relative to baseline. That is a general explanation of the endpoint’s intended role; the registry does not report the actual comparison method or enough detail to reconstruct it.

The record says measurements were collected, but were not analyzed as specified in the title. The principal investigator no longer had the raw data, and efforts to retrieve it were unsuccessful. No endpoint estimate, confidence interval, p-value, or analyzed participant count is reported in the registry record. Thus, the endpoint’s intended subject is clear at a broad level, but its operational definition and result are not available.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization assigns study conditions through a chance-based process, rather than allowing investigators or participants to choose the condition. In this study, the record lists randomized allocation and a crossover model, with high-level and low-level noninvasive ventilation as the conditions. Random assignment can reduce systematic differences in condition assignment, but it does not guarantee that the study will produce a usable analysis. The registry does not report the sequence assignments or the method used to generate them.

What a crossover comparison can estimate

In a crossover design, participants receive each condition, so the comparison can use the difference between measurements from the same person. This can control for characteristics that remain stable within that person during the study. The approach depends on valid measurement and on assumptions about order and carryover. For example, the effect of an earlier condition should not distort the later condition’s measurement in a way that is mistaken for a treatment contrast. The record does not report whether a washout was used, how condition order was handled, or how any possible carryover was assessed.

The registry identifies the study as single-masked, but does not state who was masked. Masking can reduce the influence of expectations on measurement or study conduct, depending on who is unaware of the assigned condition. Because the masked party and procedures are not reported, the practical protection against bias cannot be evaluated from this record.

Why an estimate needs uncertainty

A treatment-effect estimate describes the observed contrast between conditions. A confidence interval is a statistical range that conveys uncertainty around an estimate under the assumptions of the analysis. A narrow interval generally indicates greater precision, while a wide interval indicates less precision. The interval is not a guarantee that the true effect lies within its limits, and it does not replace consideration of study design or measurement quality. In this trial, no primary endpoint estimate or confidence interval is reported, so neither the magnitude nor precision of the contrast can be assessed.

A p-value is calculated from an estimate and a statistical model under a null hypothesis. It does not measure the size or clinical importance of an effect. The registry does not report a primary-outcome p-value. Its note that the sample size did not generate enough statistical significance is not an inferential result and cannot substitute for the estimate, uncertainty interval, or analysis details. The record does not describe a statistical model for the primary endpoint.

Sample-size illustrations and observed results

The record describes planning illustrations based on a stated fraction of an observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It specifies that non-time-to-event illustrations are expressed as participants per arm. These are described as illustrations, not as the trial’s own design justification. Sample-size illustrations are planning tools: they indicate the number of participants that might be needed under specified assumptions about an effect and analysis. They are not observed results, and they are not observed power.

For these illustrations to be interpreted, the effect used as their starting point and its source must be clear. The registry record does not report an analyzed primary effect, and the primary description says the raw data could not be recovered. The numerical details needed to assess an effect-based illustration are not reported in the registry record. Thus, the stated assumptions can be described, but they do not resolve the missing primary analysis or establish what the trial observed.

Why over-dispersion matters in general

Over-dispersion is a general statistical issue that arises when observed variability is greater than a model expects. If a model understates variability, uncertainty intervals can be too narrow and tests can appear more decisive than the data warrant. A suitable analysis may need to account for extra variability, depending on the outcome and data structure. The registry does not identify an outcome distribution, report variability for the primary endpoint, or describe whether over-dispersion was assessed. This general concept therefore explains a possible modeling concern, not a finding about this trial.

The registry lists 0 analyses and does not report a primary endpoint result. It also does not describe the statistical analysis population, handling of incomplete measurements, or model for the crossover comparison. No recalculated result is available in the record. Consequently, statistical methods can be explained in general and the stated design can be identified, but the analysis cannot be reproduced or independently checked from the registry information.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, comparisons, or time points are tested. The more tests considered, the greater the chance that at least one result may appear statistically notable by chance if no adjustment or prespecified hierarchy is used. The registry lists 3 outcome measures, and the primary outcome description refers broadly to pulmonary function and respiratory muscle pressure testing. It does not report the full outcome definitions, the number of planned comparisons, a testing hierarchy, or a multiplicity adjustment. Whether multiplicity was addressed is not reported in the registry record.

The primary outcome is explicitly described as not analyzed as specified in its title. The registry says that data were collected but that the sample size did not generate enough statistical significance, and it reports that the principal investigator no longer had the raw data on file despite efforts to retrieve it. The record therefore does not make it possible to assess missing measurements, exclusions, or the handling of incomplete outcome data. The amount and pattern of missing primary data are not reported in the registry record.

The record does not define an analysis population, such as all randomized participants or those with measurements under both conditions. Nor does it describe whether participants were excluded from an analysis, how deviations from the planned conditions were handled, or whether any sensitivity analysis was performed. These omissions limit assessment of whether the analyzed participants, had an analysis been completed, would represent the randomized enrollment.

The registry’s 0 analyses entry is consistent with the absence of a reported primary analysis, but does not establish the detailed history of any work outside the registry. The analysis population, missing-data methods, and multiplicity strategy are not reported in the registry record. Without the raw data and analysis specification, the robustness of any hypothetical result cannot be evaluated.

11. 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 0% reporting threshold.

The safety record lists separate groups for high-level and low-level ventilation. For high-level ventilation, 8 were at risk for serious adverse events and 0 serious events were reported; 8 were at risk for other adverse events and 0 other events were reported. For low-level ventilation, the corresponding counts are also 8 at risk and 0 events for both categories. Deaths are reported as 0 in each group.

These are counts recorded for the study, not evidence that an event could not occur. With enrollment of 8 and no event counts, the record gives limited information about how precisely the occurrence of uncommon harms can be estimated. A zero count in a small study can coexist with uncertainty about the underlying event risk.

The study used a crossover model, and each subject was scheduled to receive both high-level and low-level ventilation. The group-level counts therefore should not be added and described as a count of distinct participants. The registry does not report the exposure-specific timing or duration for adverse-event ascertainment beyond the arm descriptions, nor does it report event terms because no events are listed. These safety figures should be read as the adverse-event counts posted in the registry, not as a comprehensive comparison of safety between ventilation levels.

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

The registry record supports a narrow description of the study: it was a randomized, single-masked crossover study of high-level and low-level noninvasive ventilation in people with ALS, with 8 enrolled. Each subject was scheduled for 2 hours under each ventilation level. The primary outcome concerned pulmonary function and respiratory muscle pressure testing over a 5-hour timeframe.

The record does not support a conclusion about the direction or size of an acute physiological effect. The primary measurements were collected but were not analyzed as specified, and the raw data could not be retrieved. No primary estimate, uncertainty interval, or p-value is reported. It is therefore not possible to say from this record whether the measurements were higher, lower, or similar between conditions, or how precisely any contrast was estimated.

The lack of a reported significant result should not be interpreted as evidence of no difference. Conversely, the study’s stated expectation that ventilation might change respiratory tests is a hypothesis, not an observed finding. The registry’s note about sample size does not establish whether an effect was present. A design can be appropriate for a question yet still fail to provide a usable result if the outcome data cannot be analyzed or recovered.

The adverse-event counts are also limited in what they establish. The record lists 0 serious adverse events, 0 other adverse events, and 0 deaths for each condition, with 8 at risk in each group. These are reported counts, not proof of zero risk, and they do not answer the primary physiological question.

The most defensible interpretation is that the registry records the intended acute comparison, the crossover design, and limited safety counts, while leaving the primary result unavailable. The record cannot establish treatment benefit, lack of benefit, or a specific physiological consequence.

13. Why This Trial Matters Statistically

This trial is statistically notable because it illustrates the difference between collecting data and reporting an analyzable result. The registry says measurements were collected, but the primary outcome was not analyzed as specified and the raw data were no longer available to the principal investigator. Without the observations, an estimate, or its uncertainty, the central comparison cannot be evaluated.

The crossover design gives the study a clear statistical rationale for an acute comparison: each participant could serve as their own reference across high-level and low-level ventilation. This can reduce the effect of stable between-person differences. At the same time, crossover studies require careful attention to condition order, carryover, and measurement timing. Those design details are not reported, so the potential strengths of the design cannot be fully assessed.

The case also shows why a statement about insufficient sample size is not itself an analysis. Statistical significance depends on the estimated contrast and its variability, as well as the analysis plan. The registry does not report those primary-outcome quantities. A sample-size illustration cannot recover them, and planning calculations should not be mistaken for observed evidence.

Finally, the record separates safety counts from the primary physiological result. The absence of reported events in the listed groups is useful descriptive information, but enrollment was 8 and the record does not provide a precise safety estimate. Overall, the statistical importance lies in recognizing the limits of what a registered design and incomplete outcome reporting can establish.

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 is that the primary outcome has no reported analysis. The registry states that measurements were collected but not analyzed as specified in the title, and that the raw data could not be recovered despite efforts to retrieve them. As a result, no treatment contrast, estimate of uncertainty, or primary-outcome test is available for evaluation.

Enrollment was 8, and the study status is terminated. The registry’s explanation links the absence of the specified analysis to the sample size and statistical significance, but it does not provide the calculations or an analysis that would allow this explanation to be checked. The reason for termination beyond the information in the primary outcome description is not reported in the registry record.

The endpoint description is broad. It does not report units, a summary parameter, dispersion, exact tests, or how measurements were combined. Although the timeframe is 5 hours, the precise measurement schedule and the baseline comparison method are not described. The registry lists 3 outcome measures, but their complete definitions and statistical relationships are not reported in the registry record.

Further design details are absent, including condition order, washout procedures, who was masked, and the analysis method. The analysis population, handling of incomplete observations, and approach to multiple outcomes or comparisons are also not reported in the registry record. These omissions limit assessment of bias, precision, and reproducibility, in addition to the central problem of unavailable primary data.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Noninvasive Ventilation on Lung Function in Amyotrophic Lateral Sclerosis — NCT00537446.
• Registry record last updated 2020-11-27; status last verified 2020-11.
• Results first posted 2020-11-27.
• 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

The registry record describes a randomized, single-masked crossover study sponsored by Columbia University. It enrolled 8 people with amyotrophic lateral sclerosis or motor neuron disease and compared high-level with low-level noninvasive positive pressure ventilation. Each subject was scheduled to receive 2 hours under each condition. The primary outcome concerned pulmonary function and respiratory muscle pressure testing over 5 hours.

The study started in 2007-09, had a primary completion date of 2012-08, and is recorded as terminated. The primary outcome description says measurements were collected but not analyzed as specified; the raw data could not be recovered. The record lists 0 analyses. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths in each ventilation group, with 8 at risk in each. No analyzed primary result is reported in the registry record.