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

1. Trial at a Glance

This page covers the registry results for Central Auditory Processing Disorders Associated With Blast Exposure (NCT00554801), a non-randomized na study. The primary outcome is Audiological Test Results.

2. Clinical Question

3. Trial Design

This completed study is recorded as a non-randomized, parallel-group comparison with no masking. Its listed phase is NA. The intervention is audiological testing, a procedure administered to both the blast-exposed group and the control group. The design is therefore not a comparison of assigned treatments: it compares people grouped according to whether they had been exposed to a blast.

The registry describes the blast-exposed group as soldiers recently exposed to a high-explosive blast while stationed in Iraq or Afghanistan. The control group consists of people matched to that group by age, gender, and hearing loss, but without blast exposure. Both groups were to receive the same audiological testing. The record does not describe the matching procedure, recruitment criteria in detail, or how exposure status was verified.

Enrollment is recorded as 84. The registry lists a study start of 2007-10 and primary completion of 2010-12. These dates and the completed status describe the study record; they do not supply outcome results. The record identifies a primary outcome and a Quality of Life Questionnaire as a secondary outcome, but does not report numerical findings for either.

Because allocation was not randomized, the groups may differ in ways not addressed by the stated matching factors. Matching can make selected characteristics more comparable, but does not by itself eliminate differences in other characteristics or establish that exposure caused an observed outcome. The registry explicitly flags the arms as not being a like-for-like control comparison. Consequently, any interpretation should focus on the design’s limits as well as on what outcome information is actually recorded.

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.

Population: All participants who completed the study

6. Primary Endpoint

The registry lists the primary outcome as Audiological Test Results, measured over three years.

The primary outcome is titled “Audiological Test Results.” It is described as audiometric testing, with results expressed as a mean and standard deviation in decibels Hearing Level (dBHL), over a timeframe of three years. The registry description defines normal hearing as better (lower) than 25 dBHL and mild hearing loss as between 25 to 50 dBHL. These are the stated descriptions of the measure; the registry does not provide observed means, standard deviations, or category counts.

Audiometric thresholds provide a standardized way to describe hearing level. In general, a defined measure can make comparisons between groups easier to interpret than an informal description of symptoms. However, the registered endpoint is audiological test results, not a reported diagnostic count of central auditory processing disorders. The registry does not specify which individual tests were used, how test results were combined, or what value or change would be considered clinically important.

The endpoint is relevant to a study concerning auditory function after blast exposure, but its interpretation depends on the analysis and the particular measurements collected. Since neither group results nor an estimated comparison are reported in the registry record, the endpoint description alone cannot show whether hearing levels differed between groups or how precisely any difference was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary outcome represent?

The primary measure is continuous: the registry describes audiological test results as a mean with standard deviation in dBHL. In general, a mean gives a measure of the center of a set of observations, while the standard deviation describes how spread out observations are around that center. They answer different questions. A similar mean can occur in groups with different levels of variability, and a mean does not reveal every feature of the underlying distribution.

The registry gives threshold descriptions for normal hearing and mild hearing loss, but it does not report the observed measurements or the group summaries. It also does not describe whether the primary analysis was intended to compare means, categories, change over time, or another feature of the data. The record’s description of the measure should therefore not be mistaken for a complete statistical analysis plan.

What would a group comparison tell readers?

In general, an estimated contrast summarizes the observed difference between groups on a defined outcome. A confidence interval expresses uncertainty around an estimate: narrower intervals indicate greater precision under the method’s assumptions, while wider intervals indicate less precision. A confidence interval does not correct for bias from group selection, confounding, or measurement problems. The registry record does not report an estimated contrast or confidence interval for the primary outcome, so neither the size nor precision of a comparison can be evaluated.

A p-value, when reported, addresses compatibility between data and a specified statistical model or null hypothesis. It is not a measure of clinical importance, and it does not by itself establish that an association is causal. No p-value or inferential result is reported in this registry record. There is therefore no basis for describing the primary finding as statistically significant or not statistically significant.

Why does the non-randomized design matter?

Random allocation, when used, helps balance measured and unmeasured characteristics on average. This study is listed as non-randomized, so exposure groups arose from exposure status rather than random assignment. The registry describes matching on age, gender, and hearing loss. In general, matching can improve comparability for the variables used, but it cannot ensure that all relevant differences have been addressed. The record does not report other adjustment methods or an analysis accounting for matching.

The parallel-group label means the record describes separate blast-exposed and control groups. It does not establish that the groups were otherwise equivalent. The registry explicitly cautions that the arms are not a like-for-like control comparison. Thus, a group difference, if reported elsewhere, would need to be interpreted as an association unless the analysis and design justified a stronger conclusion.

How should the planning illustration be read?

The study’s sample-size assumptions are described as a planning illustration computed from the observed effect, rather than the trial’s own design. The stated assumptions include a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. The illustration is not an observed trial result and is not observed power. It cannot replace the study’s actual outcome estimates or show that an analysis was adequately powered.

In general, sample-size planning asks how much information would be needed to detect a specified effect under chosen assumptions. Those assumptions include the effect size, variability, allocation, and statistical test. If an effect is chosen as a fraction of an observed effect, the resulting planning figures depend on that reference effect and should be understood as conditional illustrations. The registry record does not report the primary outcome summaries needed to independently evaluate such a reference effect.

Over-dispersion is a general concern when observed variability exceeds what a statistical model assumes. If a model understates variability, its uncertainty estimates may be too small and its tests may be too optimistic. The registry does not report a model for the primary outcome or information that would allow assessment of over-dispersion. It would therefore be inappropriate to claim that this issue was present or was addressed.

What can be inferred from the analysis listing?

The registry lists zero analyses. This is a description of the analysis information in the record, not proof that researchers did no analysis. The record does not report the statistical model, covariates, handling of repeated measurements, missing-data method, or sensitivity analyses. Since the timeframe for the primary measure is three years, details about the timing and structure of observations would be important for understanding any longitudinal analysis, but those details are not reported in the registry record.

In general, statistical interpretation depends on more than the outcome name and study design. Readers need to know which participants contributed data, how observations were summarized, what comparison was estimated, and how uncertainty was calculated. These details are not reported for the primary outcome in the registry record. The most defensible reading is therefore descriptive: the record specifies the question, groups, and measure, while leaving the outcome analysis and its uncertainty unreported.

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("Blast-exposed", "Control Group")
n   <- c(36, 29)
m   <- c(10.8, 6.6)
sp  <- c(6, 4.2)
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  Blast-exposed  36  10.800  6.000  8.770  12.830
CARM  Control Group  29  6.600  4.200  5.002  8.198

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies two outcome measures: Audiological Test Results as the primary outcome and Quality of Life Questionnaire as a secondary outcome. It does not report a multiplicity plan, including whether or how interpretation would account for examining more than one outcome. In general, testing multiple outcomes can increase the chance of finding an apparently notable result by chance; a prespecified plan helps clarify how such results should be interpreted. No claim about adjustment or its absence in the researchers’ actual analyses can be made from this record.

The registry does not report a missing-data method, the number of participants with available primary outcome data, reasons for missing observations, or an analysis population definition. Enrollment is recorded as 84, but that does not establish how many people contributed to any particular analysis. The separate group denominators reported for adverse events should not be treated as primary-outcome analysis denominators.

These omissions affect the ability to assess risk of bias and precision. If outcome availability differed between groups or was related to hearing status, an analysis of observed data could differ from the result that would have been obtained with complete follow-up. This is a general concern, not a claim that such a pattern occurred in this study. The registry does not state whether participants were analyzed according to any particular population definition, how incomplete follow-up was addressed, or whether sensitivity analyses were performed. Those details are not reported in the registry record.

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 0% reporting threshold.

The adverse-event record lists 55 blast-exposed participants at risk and 29 control participants at risk. It records zero serious adverse events and zero other adverse events in each group. Deaths are listed as null for both groups, which means death counts are not reported in the registry record; null should not be read as zero.

These entries describe what is recorded in the adverse-event fields, not a complete assessment of safety. The registry does not provide an adverse-event collection timeframe, definitions, event-level descriptions, or details about how events were monitored. The listed study procedure is audiological testing; these figures do not establish the safety of other interventions or treatments.

Zero recorded events in the listed fields do not prove that no event occurred outside the registry’s reporting scope, nor do they quantify a comparative risk with uncertainty. The at-risk figures are specific to the adverse-event record and should not be treated as outcome-analysis denominators. The registry lists no top serious-event terms. Interpretation should remain limited to the recorded counts and the missing reporting details.

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

The record establishes that a completed, non-randomized, unmasked parallel-group study was intended to examine auditory outcomes in blast-exposed soldiers compared with controls matched by age, gender, and hearing loss. It identifies audiological testing as the procedure and describes a primary outcome measured in dBHL over three years. These details explain the study’s question and intended measurement, but they are not evidence of a particular outcome.

The registry does not report group results, an estimated association, uncertainty intervals, or statistical tests. It therefore cannot show whether audiological results differed between the groups, how large a difference might have been, or how precise an estimate was. It also cannot establish the incidence, magnitude, or timing of spontaneous recovery mentioned in the study objectives. The secondary Quality of Life Questionnaire is named, but its results are not reported in the registry record.

Even a reported difference in this design would need careful interpretation. Exposure was not randomly assigned, and matching on selected characteristics does not eliminate all possible group differences. An observed association would not, by itself, establish that blast exposure caused the difference. The record itself cautions that the arms are not a like-for-like control comparison.

The study description may help readers understand why audiological measurement was selected for a question about auditory function. It does not provide evidence for a clinical recommendation, nor does it establish that any particular care strategy is effective. The stated aim of informing clinical rehabilitation is an aim, not a result documented in the registry. The narrow conclusion is that the registry describes the design and endpoint but does not report the primary outcome findings needed to answer the stated comparison question.

14. Why This Trial Matters Statistically

This study raises an important statistical distinction between a research objective and evidence that answers it. The registry describes a question about the association between blast exposure and central auditory processing disorders, but the registered primary outcome is audiological test results. A clearly named outcome and unit help identify what was intended to be measured; without group summaries and an analysis, they do not reveal what the study found.

The non-randomized design also matters. Matching on age, gender, and hearing loss signals an effort to make groups more comparable on those characteristics, but the record does not establish balance on other factors. A design description should therefore shape the strength of any possible causal interpretation. The registry’s own caution that the arms are not a like-for-like comparison reinforces this point.

Statistical reporting is central to understanding precision. Means and standard deviations would describe the outcome distributions, while an estimated contrast and uncertainty interval would show the size and precision of the group comparison. None of those results is reported in the registry record. The record lists zero analyses, leaving the methods used to produce an estimate, if one exists elsewhere, unreported.

The planning illustration also illustrates a separate distinction: sample-size planning is not a finding and is not observed power. It rests on assumptions about the effect to detect and the analysis. Treating planning quantities as evidence of an outcome would confuse design calculations with observed data. For this record, the statistical importance lies as much in the limits of the available reporting as in the stated study question.

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 most direct limitation for interpretation is that the registry does not report primary outcome results. It gives the measure’s title, unit, summary format, and timeframe, but no observed means, standard deviations, group contrast, confidence interval, or p-value. As a result, the stated question about association cannot be answered from the registry record.

The group comparison is non-randomized. The control group is described as matched on age, gender, and hearing loss, but the record does not explain the matching method or report group characteristics that would allow readers to judge balance. Other potential differences between groups are not described. The record specifically warns that the arms are not a like-for-like control comparison.

The endpoint description is also limited. It does not identify the specific audiological tests, explain how results were combined, or state how the primary outcome would be analyzed. Although the timeframe is three years, the registry does not report the timing or structure of measurements, follow-up completeness, or handling of repeated observations. The secondary Quality of Life Questionnaire is named without results.

Analysis populations, missing-data methods, multiplicity procedures, and statistical models are not reported in the registry record. The record lists zero analyses, but does not explain whether analyses were conducted elsewhere. These omissions prevent assessment of how participant availability and analytic choices might affect any result. Adverse-event fields also have limited context: deaths are null, and the event collection timeframe and monitoring details are not reported.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Central Auditory Processing Disorders Associated With Blast Exposure — NCT00554801.
• Registry record last updated 2018-08-10; status last verified 2018-07.
• Results first posted 2014-11-13.
• 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

NCT00554801 is a completed, non-randomized, unmasked, parallel-group study titled “Central Auditory Processing Disorders Associated With Blast Exposure.” The sponsor is the VA Office of Research and Development. The record lists phase NA, enrollment of 84, a study start of 2007-10, and primary completion of 2010-12.

The study compares audiological testing in a blast-exposed group and a control group described as matched by age, gender, and hearing loss. The primary outcome is Audiological Test Results, expressed as a mean and standard deviation in dBHL over three years. Quality of Life Questionnaire is listed as a secondary outcome.

The registry record does not report primary or secondary outcome results, statistical estimates, or analysis methods. It lists zero analyses and cautions that the arms are not a like-for-like control comparison. The record supports a description of the intended question and design, but not a conclusion about the outcomes.