Central Auditory Processing Deficits Associated With Blast Exposure: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Central Auditory Processing Deficits Associated With Blast Exposure (NCT01567020), a registered phase not stated study. The primary outcome is Number of Blast-exposed Veterans With Abnormal Abilities in One or More Behavioral Tests of Central Auditory Processing.

2. Clinical Question

3. Trial Design

The registry lists this study as completed, with a start date of 2012-05 and a primary completion date of 2015-12. Enrollment is recorded as 105. The sponsor is the VA Office of Research and Development. The stated research aims are to estimate the prevalence of central auditory dysfunction among Veterans exposed to blasts, identify functional outcomes associated with abnormal central auditory processing tests, and compare patterns in blast exposure with aging and non-blast-related TBI.

The design is organized around groups defined by blast exposure, TBI diagnosis, and age. The Control group consists of non-blast-exposed people without TBI who are younger than 50. The Older group consists of non-blast-exposed people without TBI aged 50 or older. The Blast group includes participants with or without a TBI diagnosis, while the Non-Blast-Exposed TBI group is defined by non-blast exposure and a TBI diagnosis. The registry record explicitly cautions that the arms are not a like-for-like control comparison. It does not state an allocation method, and this is not described as a randomized comparison.

The listed intervention is “Diagnostic,” with type “OTHER,” consistent with an assessment-oriented study rather than an assigned therapy. The record describes a six-month timeframe for the primary outcome and includes additional outcomes concerning self-reported auditory processing, hearing ability in multitalker environments, and an electrophysiological response. It does not report a detailed schedule of assessments or enough information to establish how the groups were matched or adjusted for differences. The statistical analysis plan, including any prespecified group contrasts, is not reported in the registry record.

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: Note that some of the participants finished all of the primary outcome measures but withdrew without finishing all of the secondary tests. They are thus listed as having withdrawn but are still included here for completeness.

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 Number of Blast-exposed Veterans With Abnormal Abilities in One or More Behavioral Tests of Central Auditory Processing, measured over six months.

The primary outcome is titled “Number of Blast-exposed Veterans With Abnormal Abilities in One or More Behavioral Tests of Central Auditory Processing.” Its purpose is to characterize abnormal performance on behavioral assessments of central auditory function among blast-exposed Veterans. The record lists the outcome parameter as a mean and the measure of dispersion as a standard deviation, but does not explain how those summaries correspond to the endpoint title or how multiple test results were combined into an abnormality classification.

The listed tests assess different aspects of auditory processing. The Dichotic Digits Test and Frequency Pattern Test use the percentage of responses reported correctly. The Gaps in Noise Test measures an approximate threshold in milliseconds. The Staggered Spondaic Words Test counts errors, and the Masking Level Differences Test measures a difference in threshold between diotic and dichotic stimuli. The record provides performance ranges for these measures, with the favorable direction varying by test. It also states that results for Adaptive Tests of Temporal Resolution were not reported because of a software error in stimulus presentation.

Using multiple behavioral tests can describe different components of central auditory processing rather than relying on a single task. However, interpretation of an endpoint based on “abnormal” performance requires a stated cutoff and a rule for combining test results. Those details, along with observed values for the primary outcome, are not reported in the registry record. The listed timeframe is six months, but the record does not further clarify the timing of individual test administrations.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record labels the primary measure as continuous, with a mean as the parameter and a standard deviation as the dispersion measure. In general, a mean summarizes the central value of a quantitative measurement, while a standard deviation describes how spread out individual measurements are around that mean. These summaries are most informative when the measure and analysis population are clearly defined. Here, the primary outcome title refers to a number of Veterans with abnormal abilities, but the registry metadata identify a mean and standard deviation. The record does not explain how the two descriptions fit together, how test scores were combined, or what cutoff defined abnormal performance.

What do the behavioral test scales represent?

The tests have different units and directions. The Dichotic Digits Test is scored as the percentage of digits reported correctly, from 0 (worst performance) to 100 (best performance). The Gaps in Noise Test uses an approximate threshold in milliseconds, from 2 (best) to 20 (worst). The Staggered Spondaic Words Test counts errors, from 0 (best) to 40 (worst). The Masking Level Differences Test uses a threshold difference in decibels, from 0 (worst) to 24 (best). The Frequency Pattern Test is scored as the percentage of sequences reported correctly, from 0 (worst performance) to 100 (best performance). Because higher scores do not have the same interpretation across all tests, a combined score or abnormality rule would need to be specified before results could be interpreted consistently. Such a rule is not reported in the registry record.

What would a confidence interval tell a reader?

In general, a confidence interval describes the precision of an estimated quantity under the assumptions of the statistical method. A narrow interval indicates greater precision than a wide interval, while an interval that spans a range of plausible values reflects uncertainty about the estimate. A confidence interval is not a guarantee that the true value lies within a particular observed interval. No primary-outcome confidence interval is reported in this registry record, so its precision cannot be assessed.

What can a group comparison establish?

In general, a comparison between groups describes how their observed measurements differ under the chosen analysis. Random allocation can help balance measured and unmeasured characteristics on average, while a nonrandomized comparison may remain affected by differences between groups. The registry states that the arms are not a like-for-like control comparison and does not state an allocation method. It does not report a statistical model, covariate adjustment, or prespecified contrast. Thus, even if group summaries were available elsewhere, the information in this record would not establish that a difference was caused by blast exposure, TBI, or age.

Why does over-dispersion matter?

In general, over-dispersion occurs when observed variability is greater than a statistical model expects. If a model assumes less variability than is present, its standard errors may be too small and its uncertainty estimates too optimistic. This issue can arise for count outcomes or clustered data, depending on the data structure and model. The registry record does not report a count model or enough information about the analysis to determine whether over-dispersion was assessed. This is a general consideration, not a claim that over-dispersion occurred in this study.

What does the planning illustration represent?

In general, a sample-size planning illustration based on an observed effect asks how many participants per arm might be needed under stated assumptions to detect an effect of a specified fraction of that observed effect. The assumptions recorded for this study include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such an illustration is a planning exercise, not observed power and not evidence that the study was designed around those assumptions. The record provides no numerical planning values in the registry record for this description, and the assumptions are explicitly not the trial’s own design.

The statistical analysis plan and the methods used for the reported outcomes are not reported in the registry record. With no posted primary outcome estimates or analysis results, readers cannot assess model fit, precision, or the sensitivity of conclusions to analytical choices.

10. Multiplicity, Missing Data and Analysis Populations

The study includes several behavioral tests and additional outcomes concerning self-reported auditory processing, functional hearing in multitalker environments, and change in an electrophysiological response. When researchers assess multiple outcomes or multiple group contrasts, the chance of obtaining at least one apparently notable result can increase. Statistical approaches can address this issue by defining a primary comparison in advance or by adjusting interpretation for multiple testing. The registry record does not report a multiplicity strategy, a hierarchy of tests, or the statistical analysis plan. It lists zero analyses, so there are no posted analysis results from which to judge how multiple outcomes were handled.

The record notes that some participants completed all primary outcome measures but withdrew before finishing all secondary tests. It says those participants remain included in the primary-outcome population description. This distinction matters: completion of the primary assessments does not imply completion of every secondary assessment. The record does not state how missing secondary measurements were handled, whether any other primary measurements were missing, or whether analyses used imputation or a complete-case approach. Those details are not reported in the registry record.

The Adaptive Tests of Temporal Resolution were not reported because of a software error in stimulus presentation. This is a measurement-availability issue, rather than an ordinary missing response, and the record does not describe any replacement measure or analysis for that test. Because the primary endpoint’s relationship to individual tests and abnormality rules is not explained, the consequences of unavailable test results for the endpoint cannot be assessed. The record also does not report an analysis population definition beyond its note about participants completing primary measures while withdrawing before secondary tests.

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 reports serious and other adverse-event counts by group. For Control, Blast, Non-Blast-Exposed TBI, and Older, the number at risk is listed as 28, 46, 20, and 11, respectively. In each group, the affected count is recorded as 0 for serious adverse events and 0 for other adverse events. These are registry entries for the reported groups; they are not measures of the primary auditory-processing outcome.

A zero affected count means that the registry lists no affected participants for that event category in the reported group. It does not establish that no event occurred outside the record’s ascertainment or reporting, nor does it show that every possible safety outcome was monitored. Death counts are listed as null rather than as a numerical count. A null entry should not be interpreted as a reported zero. The record does not provide additional detail about event definitions, collection procedures, or observation time for safety reporting, so these entries should be read as limited registry data rather than a complete account of safety.

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

The registry record establishes that this was a completed study focused on central auditory processing and blast exposure, with groups distinguished by blast exposure, TBI diagnosis, and age. It describes behavioral assessments, secondary functional outcomes, and a research aim of estimating abnormal test performance among blast-exposed Veterans. It also records an enrollment of 105 and identifies a six-month timeframe for the primary outcome.

What the record does not establish is the numerical prevalence of abnormal auditory processing, the size or direction of any group differences, or the precision of an estimate. No primary outcome values, confidence intervals, p-values, or analysis results are reported. The study’s stated aims are not results, and the absence of posted estimates cannot be interpreted as evidence that groups were the same or different.

The group structure also limits causal interpretation. The registry says the arms are not a like-for-like control comparison and does not state an allocation method. Group differences could be associated with age, TBI diagnosis, blast exposure, or other differences not described in the record. The registry does not report adjustment methods or an analysis plan that would clarify how these factors were considered.

The endpoint description leaves further uncertainty because the title refers to Veterans with abnormal abilities, while the measurement metadata specify a mean and standard deviation. The record does not state the cutoff for abnormality or how several different test scales were combined. It also notes that one test’s results were unavailable because of a software error. These limitations prevent a clear reconstruction of the primary endpoint from the registry description alone.

Accordingly, the record supports a description of the research question and measurement framework, but not a conclusion about the study’s substantive findings. It should not be used by itself to claim that blast exposure does or does not cause auditory-processing deficits.

13. Why This Trial Matters Statistically

This study is statistically interesting because it brings together several dimensions that can complicate clinical and observational research: exposure history, TBI diagnosis, age, and a set of behavioral measures that use different scales. Comparing these dimensions requires clear definitions of the groups and outcomes. The registry provides group descriptions, but explicitly warns that the groups are not a like-for-like control comparison. That warning is important because descriptive contrasts between groups are not automatically adjusted estimates of an exposure effect.

The endpoint also illustrates why operational definitions matter. The primary outcome title refers to abnormal abilities in one or more tests, while the metadata describe a mean and standard deviation. The listed tests use different units and directions, and one test’s results were not reported because of a software error. Without stated thresholds and a rule for combining results, readers cannot determine exactly how the primary construct was converted into an analysis measure. This is a general challenge in multi-test studies: measurement decisions shape what a reported estimate means.

The registry record also demonstrates the difference between a completed study and a complete statistical record. It lists enrollment, groups, outcomes, and safety counts, yet it reports no analyses or numerical primary-outcome findings. A study can have a documented research aim without the registry record providing enough statistical results to evaluate that aim. Transparent reporting of estimates, uncertainty, analysis populations, and missing-data handling is essential for readers to assess both the size and reliability of findings.

Finally, the record’s note that some participants completed primary measures but not all secondary tests highlights the need to distinguish outcome-specific completion from overall study participation. That distinction affects which observations contribute to each analysis and how missingness should be interpreted. The record does not provide the details needed to evaluate those issues, making the limits of interpretation part of the statistical story.

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 registry record does not report numerical results for the primary outcome, and it lists zero analyses. This prevents assessment of the observed estimate, its precision, or any statistical comparison. The record also does not provide a confidence interval, p-value, or a detailed results account for the listed secondary outcomes.

The primary endpoint is not fully specified. Its title refers to the number of blast-exposed Veterans with abnormal abilities in one or more tests, while its metadata describe a mean and standard deviation. The record does not provide an abnormality threshold, a rule for combining the tests, or an explanation of how the endpoint was represented analytically. The tests use different scales and score directions, so the absence of a stated combination rule is consequential for interpretation.

The groups are not described as randomized or like-for-like. Allocation is not stated, and the registry does not report matching, adjustment, or a statistical model. The group definitions include blast exposure, TBI diagnosis, and age, but the record does not explain how possible differences between groups were addressed. This limits interpretation of any group contrast as attributable to a particular exposure or characteristic.

Missing-data details are limited. Some participants completed primary measures but withdrew before all secondary tests; the record says they are included in the primary-outcome population description. It does not specify how missing secondary measurements or any other missing observations were handled. Results for Adaptive Tests of Temporal Resolution were not reported because of a software error in stimulus presentation. The record does not explain whether that affected any composite or comparison.

The registry also does not report the full statistical analysis plan, multiplicity approach, detailed assessment schedule, or safety ascertainment methods. These omissions do not establish that the study lacked such procedures; they mean they are not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Central Auditory Processing Deficits Associated With Blast Exposure — NCT01567020.
• Registry record last updated 2019-06-14; status last verified 2019-03.
• Results first posted 2017-02-08.
• 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

NCT01567020 is a completed study titled “Central Auditory Processing Deficits Associated With Blast Exposure,” sponsored by the VA Office of Research and Development. The registry lists enrollment of 105, a start date of 2012-05, and a primary completion date of 2015-12. The study’s aims concern abnormal central auditory processing among blast-exposed Veterans and functional outcomes associated with test performance.

The record identifies Control, Blast, Non-Blast-Exposed TBI, and Older groups and lists behavioral and secondary functional outcomes. It cautions that the arms are not a like-for-like control comparison. No statistical analyses or numerical primary-outcome results are reported in the registry record. The primary endpoint’s abnormality rule and the handling of missing measurements are not described. The record notes that Adaptive Tests of Temporal Resolution were not reported because of a software error in stimulus presentation.