Mindfulness-Based Stress Reduction for Adults With Low-Risk Chest Pain Associated With Anxiety: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mindfulness-Based Stress Reduction for Adults With Low-Risk Chest Pain Associated With Anxiety (NCT03365375), a non-randomized na study. The primary outcome is Mean Difference in Generalized Anxiety Disorder -7 (GAD-7).

2. Clinical Question

3. Trial Design

This completed pilot trial was registered as a parallel, single-masked, non-randomized study. The registry lists enrollment of 28, a start date of 2018-01-28, and a primary completion date of 2019-08-01. The listed phase is NA. Indiana University is named as sponsor. These design details describe the registered study; they do not supply the results needed to judge the primary outcome.

The two groups were MBSR Referral and Usual Care Referral. The MBSR group was referred to a local mindfulness-based stress reduction course as well as to a primary care provider. Usual care involved referral to primary care and/or psychiatry for further management of elevated anxiety according to standard of care. The registry’s brief summary uses the word “randomized,” but the allocation field says NON RANDOMIZED, and the record flags the arms as not being a like-for-like control comparison. The non-randomized allocation is the relevant design limitation when interpreting a comparison between arms.

The trial aimed to assess feasibility and effectiveness of referral, with outcomes covering anxiety, quality of life, mindfulness measures, and Emergency Department use. Its primary outcome was GAD-7 at enrollment compared with assessment at 3 months. The record lists secondary outcomes including PROMIS Global Short Form, ED utilization, Cognitive and Affective Mindfulness Scale - Revised, and Toronto Mindfulness Scale. Details of masking, recruitment procedures, referral uptake, follow-up completion, and the statistical plan are 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

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 Mean Difference in Generalized Anxiety Disorder -7 (GAD-7), measured over Measured at 3 months.

The primary outcome is the mean difference in Generalized Anxiety Disorder-7 (GAD-7) score. The registry describes a comparison of GAD-7 score at enrollment with assessment at 3 months and identifies the measure as a score on a scale. GAD-7 is used to quantify anxiety symptoms, allowing investigators to describe symptom levels and their change over time. The record gives a range of 0-21 and describes severity categories, including mild and moderate ranges. The severe category is written as > 15 in the registry.

A continuous score preserves differences across the scale rather than reducing participants to a yes-or-no category. A mean summarizes the group’s average score, while a mean difference expresses a contrast between the values being compared. For a useful interpretation, the direction and size of the observed difference need to be reported alongside its uncertainty and the details of how the change was calculated. Those outcome estimates are not reported in the registry record. The description also does not fully clarify whether the reported primary contrast is a within-arm change, a difference in change between arms, or another specified contrast. The endpoint’s intended timing is stated, but the result and its exact comparative definition remain unavailable in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary measure as a mean difference in GAD-7 score, a continuous score with a stated range of 0-21. Continuous outcomes retain gradations in measured symptoms. A group mean gives a central summary, while the standard deviation describes how dispersed individual scores are around that mean. These quantities answer different questions: the mean describes the average level, and the standard deviation describes variation among participants.

What does a mean difference describe?

A mean difference is a contrast between averages. Its interpretation depends on which averages are contrasted. For this trial, the description refers to GAD-7 at enrollment compared with assessment at 3 months, but the registry record does not fully specify whether the primary estimate is a change within each arm, a contrast in change between arms, or a different comparison. That distinction should be clear in the analysis plan and results because the interpretations are not interchangeable.

In general, an estimate is more informative when accompanied by a confidence interval. A confidence interval describes the range of values reasonably compatible with the observed data under the statistical model. A narrow interval indicates greater precision than a wide interval, while neither width nor statistical significance alone determines clinical importance. No confidence interval for the primary outcome is reported in the registry record. A p value, if reported, would address compatibility with a specified null model; it would not by itself quantify the size or practical importance of a difference. No primary-outcome p value is reported either.

Why does allocation matter?

Random allocation aims to make comparison groups similar, on average, with respect to measured and unmeasured factors at the time of assignment. This trial is registered as non-randomized, and the record explicitly cautions that its arms are not a like-for-like control comparison. Participants entering different referral pathways may differ in ways related to anxiety scores or later outcomes. Statistical adjustment can address measured differences under appropriate assumptions, but it cannot guarantee removal of unmeasured confounding. The registry record does not report whether adjustment was used or which variables, if any, were included.

The record also describes the study as single-masked, but does not identify who was masked or how masking was maintained. This matters because knowledge of group assignment can affect behavior, delivery of an intervention, reporting of symptoms, or outcome assessment, depending on the role of the person who knows the assignment. The registry description alone does not allow readers to assess those possibilities.

How should repeated measurement be understood?

GAD-7 was described at enrollment and at 3 months. When observations are collected from the same participant over time, they are related rather than independent. A statistical method should account for that relationship if it uses both measurements. General approaches can compare change scores or model repeated measurements, but the appropriate choice depends on the analysis question, data structure, and assumptions. The method used for this trial is not reported in the registry record.

For continuous outcomes, model assumptions can include how the outcome is distributed and whether variability is similar across groups. If data are highly skewed or include unusual values, a mean and a model based on it may not fully represent the pattern. Over-dispersion generally means observed variability is greater than a model expects; failing to account for it can make standard errors too small and confidence intervals too narrow. This is a general statistical concern, not a reported finding about this trial. The registry record does not report distributional checks, model diagnostics, or any alternative analysis.

What do the planning illustrations mean?

The registry’s sample-size assumptions describe planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. The listed convention is participants per arm for non-time-to-event outcomes. Such calculations illustrate the sample size associated with a chosen effect under stated assumptions; they are not the trial’s original design justification and do not establish the probability that this completed study detected an effect. They should not be read as observed power. The registry record does not report the trial’s own sample-size justification, target effect, or planned power.

Finally, a statistical analysis depends on who is included and how incomplete observations are handled. Complete-case analysis uses participants with the required measurements, while other approaches may make assumptions about missing values. Those choices can affect estimates, especially when missingness is related to participant characteristics or outcomes. The registry record does not report the analysis population, missing-data method, or outcome-specific number analyzed.

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("Usual Care Referral", "MBSR Referral")
n   <- c(12, 6)
m   <- c(5.3, 3.2)
sp  <- c(5.4, 8.1)
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  Usual Care Referral  12  5.300  5.400  1.869  8.731
CARM  MBSR Referral  6  3.200  8.100  -5.300  11.700

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures, including GAD-7, ED utilization, PROMIS Global Short Form, Cognitive and Affective Mindfulness Scale - Revised, and Toronto Mindfulness Scale. It also lists one analysis, but does not identify the analysis details or explain how it relates to the full set of outcomes. A multiplicity adjustment, hierarchy of outcomes, or other strategy for interpreting multiple comparisons is not reported in the registry record.

As a general statistical principle, examining many outcomes or contrasts creates more opportunities for chance findings. Prespecifying a primary outcome and clarifying which analyses are confirmatory can help distinguish the main question from exploratory work. The primary outcome is named as mean difference in GAD-7, but the record does not report a complete analysis plan, planned contrasts, or any adjustment procedure. It is therefore not possible to assess how multiplicity was handled.

Missing-data handling is also not reported in the registry record. The registered outcome description gives enrollment and 3-month assessment timing, but no counts of participants with observed scores at each time point, reasons for missing assessments, or methods for accounting for missing data. The number enrolled should not be assumed to equal the number analyzed for the primary outcome.

The registry record does not specify the analysis population, such as whether analyses included everyone enrolled, participants who completed follow-up, or another defined group. It also does not report whether any exclusions were made after enrollment. These omissions matter because outcome estimates can depend on which participants contribute data and on assumptions used to handle missing observations. Without those details, readers cannot assess the robustness of the primary analysis or determine whether the posted result reflects all enrolled participants.

12. 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 registry lists serious adverse events and other adverse events separately for each referral group. For Usual Care Referral, 14 participants were at risk for each category; 0 serious events, 0 other events, and 0 deaths are listed. For MBSR Referral, 14 participants were at risk for each category; 0 serious events, 0 other events, and 0 deaths are listed. No top serious-event terms are listed.

These entries mean that the registry reports zero events in the listed categories for the stated at-risk groups. They do not establish that the risk of an event is absent. A zero count in a study of this size can coexist with uncertainty about uncommon events, and the record does not provide further detail on event collection, definitions, follow-up duration for safety, or completeness of reporting. The figures should be read as the recorded safety counts, not as proof of no possible harm.

The registry describes a non-randomized comparison, so the group counts should not be interpreted as a controlled estimate of relative safety. The record does not report a formal statistical comparison of adverse events. These safety summaries provide descriptive information only and do not establish a causal difference between referral strategies.

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

The registry record establishes that this completed pilot trial examined referral to a local mindfulness-based stress reduction course alongside primary care referral, compared with usual-care referral for elevated anxiety. Its primary measure was GAD-7, with enrollment and 3-month assessment described. The record also identifies outcomes spanning quality of life, mindfulness, and Emergency Department use. These details clarify the study question and the range of outcomes considered.

However, the primary GAD-7 result is not reported in the registry record. There is no posted mean difference, arm-specific outcome summary, confidence interval, or p value from which to describe the observed pattern or its precision. It is not possible to say from this record whether the scores changed, how they compared across the referral groups, or whether an estimate was compatible with a range of clinically meaningful effects.

The non-randomized design further limits causal interpretation. People in the MBSR Referral and Usual Care Referral arms may differ in ways that also relate to anxiety, follow-up, or service use. The record itself notes that the arms are not a like-for-like control comparison. Any unadjusted difference, if one were available, would be an association between group membership and outcome rather than a secure estimate of the effect caused by referral.

As a pilot, the study may be relevant to questions about the feasibility of referral and the selection of outcomes for further evaluation. But the registry does not report referral uptake, course attendance, retention, or outcome completion. Nor does it report the statistical plan needed to evaluate the primary contrast. The safety entries list no serious or other adverse events and no deaths in either group, but those counts do not prove absence of risk.

The appropriate reading is therefore limited: the record describes a pilot comparison and its intended outcome framework, while leaving the primary results and important analysis details unreported. It cannot support a conclusion about the effect of MBSR referral on anxiety or other outcomes.

14. Why This Trial Matters Statistically

This trial raises statistical issues that commonly arise when evaluating behavioral referrals in clinical settings. The question involves a continuous symptom measure at enrollment and follow-up, a comparison between referral pathways, and outcomes beyond anxiety. Distinguishing a within-group change from a between-group contrast is essential: improvement over time in one group alone does not show how that group compares with another pathway.

Non-randomized allocation is especially important. In a randomized study, assignment is designed to reduce systematic differences between groups. In this trial, the registry says allocation was non-randomized and warns that the arms are not a like-for-like control comparison. This means that observed group differences could reflect differences in the participants or care context as well as the referral strategy. Clear reporting of baseline characteristics, adjustment methods, and assumptions would help readers judge that concern, but these details are not reported in the registry record.

The trial also illustrates why estimates and uncertainty matter more than a bare statement that an outcome was measured. A mean difference paired with a confidence interval would show both the estimated contrast and how precisely it was estimated. The registry does not report that primary result. Enrollment alone cannot substitute for outcome data, and a planning calculation cannot establish what the completed study observed.

Finally, a pilot’s value may include learning about implementation and measurement, not only estimating an effect. Yet feasibility outcomes such as referral uptake and follow-up completion are not reported in the registry record. Transparent reporting of those measures, along with missing-data handling and the multiplicity approach, would help place any future efficacy estimate in context. These gaps make the registry record informative about the study’s design, but limited for evaluating its statistical findings.

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 principal limitation for interpreting this trial is that the registry record does not report the primary GAD-7 result. Without arm-level scores, a defined contrast, and an uncertainty estimate, the observed anxiety pattern cannot be assessed. The endpoint description gives enrollment and 3-month timing but does not fully clarify whether the primary estimate compares within-arm change or change between arms.

The non-randomized allocation is a further trial-specific limitation. The registry explicitly cautions that the referral arms are not a like-for-like control comparison. Differences in participant characteristics, referral preferences, access to services, or other factors could influence outcomes; whether the analysis accounted for measured differences is not reported in the registry record. The brief summary’s use of “randomized” conflicts with the allocation field’s non-randomized designation, so the registered allocation description and the stated caution should guide interpretation.

The record does not report who was masked, the statistical model, covariate adjustment, distributional checks, outcome-specific analysis counts, or missing-data methods. It also does not report referral uptake, MBSR course attendance, follow-up completion, or the trial’s sample-size justification. Those omissions limit assessment of intervention exposure, analysis reliability, and feasibility.

Although the registry lists several secondary outcomes and one analysis, it does not provide the analysis plan or multiplicity strategy. The safety record lists zero serious events, zero other events, and zero deaths in both arms, but provides no further event-collection details. These limitations mean the registry record supports a description of the registered pilot design, not a complete assessment of its outcome findings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Mindfulness-Based Stress Reduction for Adults With Low-Risk Chest Pain Associated With Anxiety — NCT03365375.
• Registry record last updated 2024-01-24; status last verified 2023-05.
• Results first posted 2024-01-24.
• 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

NCT03365375 is a completed, parallel, single-masked, non-randomized pilot trial sponsored by Indiana University. The registry lists enrollment of 28 and dates of 2018-01-28 for study start and 2019-08-01 for primary completion. It compares referral to a local mindfulness-based stress reduction course plus primary care referral with usual-care referral for adults with low-risk chest pain associated with anxiety.

The primary outcome is mean difference in GAD-7 score, measured at enrollment and assessed at 3 months. Secondary outcomes include ED utilization, PROMIS Global Short Form, Cognitive and Affective Mindfulness Scale - Revised, and Toronto Mindfulness Scale. The registry record does not report the primary outcome estimate or its uncertainty, nor does it detail the analysis plan, missing-data methods, or analysis population. The safety entries list zero serious events, zero other events, and zero deaths in each arm. The registry cautions that the non-randomized arms are not a like-for-like control comparison.