Treatment of Older Veterans With Chronic Posttraumatic Stress Disorder: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Treatment of Older Veterans With Chronic Posttraumatic Stress Disorder (NCT00539279), a randomized na study. The primary outcome is PTSD Checklist (PCL).

2. Clinical Question

The study also set out to examine whether executive functioning modifies response to treatment. Its stated hypothesis was that participants with impaired executive functioning would show a smaller reduction in PTSD symptoms. This is a question about whether treatment-related symptom change differs across levels of executive functioning, not simply whether one group has a lower average score.

The project’s brief summary additionally describes hypotheses concerning depressive symptoms and functional impairment. Those aims sit alongside the primary PCL outcome, but the registry record does not provide their results or explain how they were prioritized in the statistical analysis. The record lists other outcome measures, including posttraumatic cognitions, state anxiety, disability, and a standardized composite of neuropsychological deficits.

Because the primary measure is recorded at multiple time points and the registry does not reduce it to one comparison, the available record does not establish how the observed symptom patterns differed between groups. It supports describing the research question and design, but not concluding whether either treatment had a larger measured effect.

3. Trial Design

This was a randomized, parallel-group trial with single masking. The registry reports enrollment of 87 and lists two behavioral interventions: Prolonged Exposure Therapy (PE) and Relaxation Training (RT). It identifies the US Department of Veterans Affairs as the sponsor. The study status is completed; the start is recorded as 2009-03 and primary completion as 2013-03.

The target population was older veterans with chronic PTSD. The registry record does not report the age threshold used to define older participants, additional inclusion or exclusion criteria, the method used to generate the random sequence, allocation concealment procedures, or which study participants or personnel were masked. “Single” masking identifies the recorded masking category, but does not specify the masked role in the information.

The parallel-group structure means participants were assigned to one of the two treatment conditions rather than crossing between both conditions as part of a crossover design. Random allocation is intended, in general, to make treatment groups comparable on average at the point of assignment. It does not guarantee that every measured or unmeasured characteristic will be balanced in a particular trial. The registry does not report whether allocation was stratified or whether any baseline adjustment was planned.

The primary outcome was the PTSD Checklist (PCL), assessed pre-treatment, post-treatment, and at 6-month follow-up. The record characterizes the primary summary as a median with standard deviation dispersion, but does not give outcome values by group or time point. It lists secondary outcomes of the Posttraumatic Cognitions Inventory, State-Trait Anxiety Inventory State Scale, Sheehan Disability Scale, and Global Neuropsychological Deficits (Standardized, Composite). The registry lists 7 outcome measures, but no analysis entries.

The phase is recorded as NA. The registry record does not report the treatment duration, session schedule, follow-up retention, or details of how therapies were delivered. Those omissions limit interpretation of the practical features of the comparison; they do not change the stated randomized, parallel design.

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.

Treatment

Reasons for not completing this period:

Post-Treatment Assessment

Reasons for not completing this period:

6-Month Follow-Up Assessment

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 PTSD Checklist (PCL), measured over Pre-treatment, post-treatment, and 6-month follow-up.

The primary endpoint is the PTSD Checklist (PCL), a self-report questionnaire about PTSD symptoms. The version used was the PCL-S, which asks participants to respond with a specific traumatic event in mind. It has 17 items, each with response categories from 1 to 5, and a total score ranging from 17 to 85. Higher scores indicate higher levels of PTSD symptoms. A score of 50 or above is commonly interpreted as designating clinically significant PTSD symptoms.

Using a symptom questionnaire provides a defined way to quantify participants’ reported symptoms and compare scores across assessments. The PCL is listed at pre-treatment, post-treatment, and 6-month follow-up, so the stated schedule can describe both immediate post-treatment status and later symptom status. A score threshold can help characterize symptom severity, but crossing or not crossing that threshold is not itself a treatment-effect estimate.

The registry labels the summary parameter as median and the dispersion as standard deviation. These describe different features: the median is a measure of the center of a score distribution, while standard deviation describes spread around the mean. In general, the median and standard deviation do not fully describe a distribution, and their pairing can make interpretation less straightforward than a familiar mean-and-standard-deviation summary. The registry record does not explain the reason for this choice or provide the underlying group values.

No PCL scores, change estimates, confidence intervals, or test results are reported in the registry information summarized for this trial. Therefore, the endpoint definition and schedule can be described, but the magnitude and precision of any group difference cannot.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study is recorded as randomized, single-masked, and parallel-group. These labels describe broad design features; they do not supply all details of how the trial was conducted or analyzed. The registry does not report the randomization procedure, allocation concealment, the masked role, the planned model for repeated PCL measurements, or the statistical analysis plan.

What does randomization contribute?

In general, random assignment is used to reduce systematic differences between treatment groups at the start of a study. It can balance both measured and unmeasured characteristics on average across repeated studies, but chance imbalances can remain in any one trial. Randomization alone does not show that outcome measurement was unbiased, that follow-up was complete, or that an analysis appropriately handled missing observations.

The parallel structure assigns participants to one treatment condition for the comparison. The record lists PE and RT as behavioral interventions. It does not describe treatment dose, adherence, therapist training, treatment fidelity, or whether participants received other care during follow-up. Those details could help explain how the intervention contrast was implemented, but are not reported in the registry information.

How should repeated measurements be understood?

The primary PCL assessment was scheduled pre-treatment, post-treatment, and at 6-month follow-up. Repeated assessments can distinguish baseline symptom levels, post-treatment status, and later status. In general, an analysis may compare groups at a specified time, compare changes from baseline, or model the pattern across all assessments. These approaches answer related but not identical questions, and their estimates can differ. The registry does not identify which approach was used.

The registry explicitly indicates that the primary outcome has several categories or time points and was not reduced to one comparison. Consequently, the record does not supply a single PCL contrast to interpret. It also lists zero analysis entries. That describes the absence of analyses in the registry record; it does not establish that no analysis was conducted outside that record.

What do the summary statistics mean?

The recorded primary parameter is the median, with standard deviation as the dispersion measure. In general, the median marks the middle of an ordered set of scores, whereas standard deviation describes variability around the mean. The median is often useful when distributions are asymmetric or contain extreme values. Standard deviation is most directly interpretable as spread when the mean and distributional shape are also understood. The registry does not explain its choice of summaries, report the score distributions, or provide the group summaries.

For treatment comparisons, an effect estimate should be considered together with its uncertainty. A confidence interval communicates precision and the range of effects compatible with the observed data under the statistical model. A p-value, when reported, addresses compatibility with a null hypothesis under model assumptions; it does not measure clinical importance or the probability that a treatment hypothesis is true. Neither confidence intervals nor p-values for the PCL comparison are reported in the registry information.

Why does over-dispersion matter in general?

For outcomes that are counts, over-dispersion means that variability exceeds what a simple count model assumes. If ignored, standard errors can be too small and intervals too narrow, making uncertainty appear less than it is. The primary outcome in this trial is a questionnaire score, not a count outcome, and the registry does not report an analysis model. This general point should not be read as a statement that over-dispersion was present or relevant to the trial’s analysis.

What do the planning assumptions describe?

The registry describes sample-size calculations as planning illustrations based on the observed effect, not as the trial’s own design. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. Such calculations are prospective planning aids: they estimate the number of participants per arm that might be needed under the stated assumptions to detect a target effect. They are not observed power and do not show that the trial was adequately powered.

In general, planning calculations depend on the target effect, variability, significance level, allocation, and analysis assumptions. If the target is a fraction of an observed effect, the illustration’s interpretation depends on that observed effect and on the calculation method. The registry record does not report the study’s own sample-size justification or establish that these illustrative assumptions guided trial design. Any numeric planning outputs should therefore be read as illustrations rather than as evidence about the trial’s actual power or results.

The summary label “median” alongside standard deviation, the lack of a reduced primary comparison, and the absence of analysis entries mean that the record does not reveal the statistical model or the inferential procedure used for the stated hypothesis. Descriptions of general methods clarify what such analyses could mean, but cannot substitute for a reported analysis.

10. Multiplicity, Missing Data and Analysis Populations

The study names multiple research questions and outcomes. The brief summary describes hypotheses about PTSD symptoms, depressive symptoms, functional impairment, and whether executive functioning modifies treatment response. The registry lists secondary outcomes covering posttraumatic cognitions, state anxiety, disability, and a standardized composite of neuropsychological deficits. It also records 7 outcome measures. Examining multiple outcomes or time points creates a multiplicity concern: the more statistical questions considered, the greater the chance of at least one apparently notable result arising by chance if all are tested without an appropriate plan.

In general, a statistical plan may address multiplicity by identifying a primary comparison, ordering tests, adjusting significance thresholds, or emphasizing estimation and uncertainty rather than a collection of isolated tests. The registry record does not report a multiplicity strategy, a hierarchy of outcomes, or how the stated hypotheses were handled. Since the primary PCL outcome has several categories or time points and is not reduced to one comparison, the record does not identify which contrast should be treated as the primary inferential test.

The registry reports zero analysis entries. It does not report how missing PCL assessments were handled, whether analyses used all randomized participants or another analysis population, or whether exclusions occurred after randomization. The number of participants contributing outcome data at each time point is not reported in the information. Without these details, readers cannot assess the potential influence of attrition or missing-data assumptions on any treatment estimate.

These omissions do not establish that the trial lacked a statistical plan or that analyses were not conducted. They mean only that those methods are not reported in the registry record. The distinction matters because analysis choices, missing-data handling, and outcome prioritization affect how results should be interpreted.

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 serious adverse-event entries report zero affected participants in the PE group, with 41 at risk, and zero affected participants in the RT group, with 46 at risk. The other adverse-event entries likewise report zero affected participants, with 41 at risk in PE and 46 at risk in RT. These are the registry’s recorded counts for the categories shown.

A zero count in a registry entry means that no affected participants were entered for that category in the record; it does not establish that an intervention carries no risk. In general, the ability to interpret event counts depends on what events were sought, how they were defined, the observation period, completeness of reporting, and whether events were considered related to treatment. The registry information does not report these details or list serious-event terms.

The death fields are null. A null entry is not the same as a reported zero, so the record does not establish a death count. The safety figures should be read separately from the primary symptom outcome: they do not indicate whether PCL scores differed, and the absence of recorded events in these categories does not resolve the efficacy question.

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

The registry record establishes that a randomized, parallel-group comparison of PE and RT was conducted in older veterans with chronic PTSD. It identifies the PCL as the primary outcome, describes its score interpretation, and records assessments before treatment, after treatment, and at 6-month follow-up. It also records the study as completed and identifies its sponsor and broad design features.

It does not establish how the two groups’ PTSD symptom scores compared. No group-level PCL values, effect estimate, confidence interval, or test result is reported in the information. The stated primary hypothesis is not a result, and the record’s multiple outcome time points are not reduced to a single comparison. Therefore, readers cannot infer from this record whether scores were higher or lower in either group, whether a difference was precise, or whether a change was clinically meaningful.

The record also cannot establish whether executive functioning modified treatment response, or whether depressive symptoms, functional impairment, or the listed secondary outcomes differed between groups. These are stated aims or registered outcomes, not reported findings in the analysis information.

The safety entries record no affected participants in the reported serious and other adverse-event categories, but null death entries do not provide a death count. The safety information does not establish absence of all adverse events or provide the context needed to assess their ascertainment.

In general, interpretation of a randomized trial requires outcome estimates, uncertainty, analysis methods, and information about missing observations. Those pieces are not reported for the main symptom comparison in this registry record. The appropriate conclusion is limited: the study’s question and design are documented, while its primary comparative result cannot be determined from the registry information presented.

13. Why This Trial Matters Statistically

This trial is statistically notable because its central question involves both a treatment comparison and possible variation in response by executive functioning. A treatment contrast asks whether outcomes differ between PE and RT on average under a defined analysis. Effect modification asks whether that contrast changes across cognitive-function levels. These are distinct statistical questions and generally require distinct estimates and uncertainty measures.

The primary PCL outcome was scheduled at multiple assessments. Such repeated measurements can support several legitimate comparisons, including post-treatment status, change from baseline, or a trajectory across time. The registry’s indication that the outcome was not reduced to one comparison highlights why specifying the estimand—the exact quantity the analysis aims to estimate—is important. Without that specification and the corresponding results, a reader cannot identify which treatment contrast answers the primary question.

The study also lists multiple secondary outcomes and hypotheses. In general, a clear hierarchy and multiplicity strategy help distinguish a principal confirmatory question from additional exploratory questions. The registry record does not report those statistical choices. This is relevant to interpretation because isolated findings across many measures can be difficult to evaluate without prespecified priorities and transparent uncertainty.

The record’s planning illustrations are also distinct from the trial’s design justification. Calculations based on an observed effect can illustrate future study requirements under assumptions, but they do not indicate the trial’s observed power or demonstrate that the original study was planned around those calculations.

Finally, the registry illustrates the difference between registration details and a complete results report. It documents population, interventions, design, outcome definitions, and some adverse-event counts, but does not report the primary outcome analysis. That gap limits statistical conclusions even when the research question and measurement schedule are clear.

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 most consequential trial-specific limitation for interpretation is that the registry record does not report the primary PCL results or a single comparison across its multiple time points. Without group summaries, an effect estimate, and uncertainty, the direction and precision of the treatment contrast cannot be assessed. The record also lists zero analysis entries, so there are no recorded statistical results for the primary or secondary outcomes in the information.

The record does not report the detailed analysis plan, including the model for repeated PCL assessments, the population included in each analysis, or how missing outcome observations were handled. Follow-up completeness and the number contributing data at each assessment are not reported. These omissions prevent assessment of whether missingness or analysis-population choices might affect a result.

Several design and implementation details are also not reported: the age threshold for “older,” detailed eligibility criteria, the randomization method, allocation concealment, the role masked under single masking, intervention dose and delivery, adherence, and treatment fidelity. Their absence from the registry information limits assessment of generalizability and how closely the intervention groups represented the intended treatments; it does not prove these details were absent from trial conduct or other documentation.

The primary summary is described as median with standard deviation dispersion, without an explanation of the choice or reported distributions. This makes it difficult to understand the intended analytic approach. The stated hypotheses span multiple outcomes and effect modification, while a multiplicity strategy is not reported. Finally, adverse-event counts lack reported ascertainment details and observation context, and null death entries cannot be interpreted as zero deaths.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Treatment of Older Veterans With Chronic Posttraumatic Stress Disorder — NCT00539279.
• Registry record last updated 2015-08-19; status last verified 2015-08.
• Results first posted 2015-08-19.
• 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

NCT00539279, “Treatment of Older Veterans With Chronic Posttraumatic Stress Disorder,” is recorded as a completed randomized, single-masked, parallel-group trial sponsored by the US Department of Veterans Affairs. Enrollment is listed as 87. The study compared Prolonged Exposure Therapy (PE) with Relaxation Training (RT) in older veterans with chronic PTSD.

The primary outcome was the PCL, assessed pre-treatment, post-treatment, and at 6-month follow-up. Higher scores indicate greater PTSD symptoms; a score of 50 or above is commonly interpreted as designating clinically significant symptoms. Secondary measures include posttraumatic cognitions, state anxiety, disability, and a standardized neuropsychological-deficit composite.

The registry record states that the primary outcome’s multiple time points were not reduced to one comparison and lists zero analysis entries. It does not report the primary outcome results, a statistical analysis plan, or missing-data methods. Serious and other adverse-event entries list zero affected participants in both groups; death fields are null rather than reported zeros.