Effectiveness of Standardized Respiratory Physiotherapy in Primary Care (FREAP): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effectiveness of Standardized Respiratory Physiotherapy in Primary Care (FREAP) (NCT01152762), a randomized na study. The primary outcome is St-George Respiratory Questionnaire-SGRQ.

2. Clinical Question

The trial was randomized and parallel-group, with 129 participants enrolled. The primary comparison reports a mean score of 29.6 for the physiotherapy group and 38.0 for the control group. Higher SGRQ scores indicate more limitations, so the posted group means describe fewer measured limitations on average in the physiotherapy arm. The comparison is a group-level result at six months; it does not establish how each participant changed from their own starting score. The registry record does not report baseline SGRQ results or a change-from-baseline analysis.

3. Trial Design

This was a randomized, parallel-group trial with no masking. The registry record lists 129 participants enrolled and identifies COPD as the condition. The trial status is completed. The recorded start was 2007-09 and primary completion was 2008-07. The sponsor was Fundacio d'Investigacio en Atencio Primaria Jordi Gol i Gurina.

One group received Standardized Respiratory Physiotherapy, while the comparator was described as usual clinical practice. The intervention description includes an initial health education session in a primary-care health centre and a course of breathing exercises and aerobic physical training. It states three sessions a week for three weeks, but the remaining intervention description is incomplete in the registry record. The registry intervention label for the comparator says placebo primary-care procedure, whereas its arm description says usual clinical practice. This difference in wording is present in the record and should be kept in mind when characterizing the comparison.

The primary outcome was the St-George Respiratory Questionnaire score at six months, reported as a mean with standard deviation. The primary outcome description states that 7 participants were excluded from the analysis. The posted arm summaries include 62 participants in the physiotherapy group and 60 in the control group. The registry record does not report why participants were excluded, how missing outcome measurements were handled, or whether the analysis followed an intention-to-treat principle.

The registry record lists two outcome measures and no posted secondary results. It also reports no analyses in its analysis count. The original sample-size justification, planned statistical analysis details, and any interim-analysis plan are not reported in the registry record. Consequently, the planning figures associated with the observed difference should be read as illustrations, not as a description of the trial’s original 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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: 7 participants were excluded from the analysis

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 St-George Respiratory Questionnaire-SGRQ, measured over Six months.

The primary endpoint is the St-George Respiratory Questionnaire, or SGRQ, score at six months. The questionnaire is designed to measure the impact of respiratory symptoms and their treatment on daily life. It includes topics related to symptoms, activity limitations, and overall well-being. The registry description says it has 50 items with 76 weighted responses, with scores ranging from 0 to 100; higher scores indicate more limitations.

This endpoint is useful for describing respiratory health from the perspective of its effects on everyday life, rather than relying only on a physiological measurement. A score provides a continuous measure, so results can be summarized using a mean and standard deviation, as they are in the posted arm results. The score’s interpretation depends on its direction: a lower score corresponds to fewer limitations, while a higher score corresponds to more limitations.

The posted endpoint is a score at six months. No baseline score or change-from-baseline result is reported in the registry record. The primary outcome description says that 7 participants were excluded from the analysis, but it does not specify the reasons or the method used to address any missing scores. The registry record also does not report a threshold for a clinically important difference. The result therefore describes the reported group scores and their statistical precision, but the record does not provide a basis for assigning a clinical-importance threshold to the observed contrast.

7. Results Posted in the Registry

• Control Group: mean 38.00 versus 29.60 on control; difference 8.40 (95% CI 1.01 to 15.79), standardized effect d = 0.40; z-test p = 0.026.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant’s SGRQ is a score on a scale. A common way to summarize a continuous outcome is to report a group mean and standard deviation. The mean describes the average score in the group, while the standard deviation describes how dispersed individual scores are around that mean. The posted results use this approach, reporting a mean of 29.6 with a standard deviation of 20.5 for the physiotherapy group and a mean of 38.0 with a standard deviation of 21.1 for the control group.

What does a mean difference represent?

A mean difference compares the average score in one group with the average score in the other. Here, the posted comparison gives a mean difference of 8.4 points. The comparison lists the control group as the comparison arm and the group means as 29.6 and 38.0. Because higher SGRQ scores mean more limitations, the lower average score is in the physiotherapy group. The score-scale difference retains the questionnaire’s original units, making it more directly interpretable than a standardized measure.

The comparison also reports a pooled standard deviation of 20.8 and a standardized effect size of 0.404. Standardization expresses the mean contrast relative to the spread of scores, which can help describe the size of a difference on a scale that is not tied to SGRQ points. It should not be confused with a change in the questionnaire scale or a clinical threshold. No clinical-importance threshold is reported in the registry record.

What does the confidence interval describe?

A confidence interval describes the precision of an estimate under the statistical model and assumptions used. A narrower interval indicates greater precision; a wider interval indicates greater uncertainty about the range of plausible values. The 95% confidence interval for the mean difference is 1.015 to 15.79. It communicates uncertainty around the estimated group contrast, rather than the range of individual participants’ scores. It also does not mean there is a 95% probability that the true value lies in this particular interval.

How should the p-value be read?

The reported p-value is 0.026 and is identified as unadjusted. In general, a p-value measures how incompatible the observed data are with a specified null model, assuming that model and the analysis assumptions hold. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. Because the value is unadjusted, it does not account for possible testing across multiple outcomes or analyses. The registry record does not report a multiplicity-adjustment plan, so the status of any such adjustment cannot be established.

The record does not state the exact test used to produce the posted p-value or confidence interval, nor does it report whether the comparison was adjusted for baseline scores or other variables. The numbers therefore support interpretation of the posted unadjusted comparison, but not assumptions about unreported analysis details. The randomized parallel-group design identifies how groups were assigned; it does not by itself establish every feature of the statistical analysis.

Why can variability matter?

When observations vary substantially within groups, a given difference between group means is harder to estimate precisely than it would be with less variability, all else being equal. The standard deviations of 20.5 and 21.1 describe the observed spread in each group. The confidence interval incorporates uncertainty in the estimated mean difference. These summaries help distinguish the estimated average contrast from the variation among participants.

General statistical context: over-dispersion occurs when data vary more than a chosen statistical model assumes. For a continuous questionnaire score, the reported standard deviations provide a direct description of observed spread; the registry record does not report an over-dispersion analysis or a model requiring such an assessment. In other settings, ignoring extra variation can make standard errors too small and intervals too narrow. That general concern should not be taken as evidence that over-dispersion affected this particular result.

What is not established by these methods?

The posted comparison is an unadjusted group-level result. The registry record does not report a baseline-adjusted model, a missing-data method, or an analysis population definition beyond the note that 7 participants were excluded from the primary outcome analysis. It does not provide participant-level data, so distributional assumptions, outliers, and within-person changes cannot be independently assessed from the posted summaries. It also does not report a protocol-defined threshold for a meaningful SGRQ difference.

These limitations do not erase the reported estimate; they define its scope. The result is a comparison of reported six-month means among the analyzed participants. The confidence interval and p-value quantify uncertainty within the posted comparison, but they do not address uncertainty caused by unreported exclusions, missingness, selective outcome reporting, or differences between the registry entry and the conduct of the trial.

10. Confidence Intervals and Precision

The posted mean difference is 8.4 SGRQ points, and its 95% confidence interval ranges from 1.015 to 15.79. The interval gives a measure of statistical precision around the estimated average contrast. It spans values that differ meaningfully in magnitude, so the point estimate should not be read as the only plausible size of the group difference. Both limits are above zero, which is consistent with a positive control-minus-intervention contrast as reported.

In general, a confidence interval is constructed by a method that, under its assumptions, would cover the true parameter in a specified proportion of repeated studies. It does not describe the spread of individual participant scores, nor does it give a probability for the true effect in this single trial. The interval’s interpretation also depends on the analysis method, which is not described in detail in the registry record.

The group means were 29.6 and 38.0, with standard deviations of 20.5 and 21.1. The spread within each group is relevant because the endpoint varies considerably across participants, while the comparison estimates a difference between averages. The confidence interval captures sampling uncertainty for that comparison, but it cannot resolve limitations arising from the 7 exclusions noted in the endpoint description. Reasons for exclusion and missing-data handling are not reported in the registry record.

The unadjusted p-value is 0.026. It indicates evidence against a no-difference model under the analysis assumptions, but does not measure precision or importance by itself. No clinical-importance threshold is reported. Therefore, the interval can be used to understand the range and precision of the statistical contrast, but it cannot determine whether values within that range would be considered important in practice.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed effect, not the trial’s original design calculations. They are participants per arm, not total event counts. In general, power is the probability that a planned analysis will reject a specified null hypothesis when an effect of the chosen size is present, under the assumptions used for planning. The 80% and 90% columns describe planning for those respective power levels; they do not describe the probability that the observed result is true.

The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set at a stated fraction of the observed effect. The registry record does not report the original trial’s sample-size assumptions or justification. These illustrations should therefore be read only as hypothetical planning scenarios based on the posted comparison.

The rows describe planning for 100%, 75%, and 50% of the observed effect. Smaller effects require more participants to achieve the same planned power, because a smaller group contrast is harder to distinguish from random variation. The required participants per arm also differ between the 80% and 90% power targets: a higher target power requires more participants under the same other assumptions.

This is not observed power. It is a forward-looking illustration of sample sizes under specified assumptions, not a retrospective measure of how much power the completed trial had. It does not account for unreported features of the original design or analysis, and it should not be interpreted as a guarantee that a future study with the listed number of participants would produce a particular result.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 8.400; pooled standard deviation σ = 20.797.
2. n = 2 × (1.96 + 0.842)² × 20.797² / 8.400² = 96.2, rounded up to 97 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 8.4                      # observed difference in means
sigma <- 20.7971632680998                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1152762)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 97 (80% power), 129 (90% power)
 75% of observed effect: n per arm = 172 (80% power), 230 (90% power)
 50% of observed effect: n per arm = 385 (80% power), 516 (90% power)
power.t.test: 97.2 
Simulated power at n = 97 per arm: 0.796 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures, but the posted primary result concerns the SGRQ score at six months. No secondary results are posted, and the record reports zero analyses in its analysis count. These details do not establish how many outcomes or analyses were originally planned, or which comparisons were prespecified. A multiplicity plan—such as a method for controlling the chance of false-positive findings across multiple tests—is not reported in the registry record.

The p-value for the primary comparison is described as unadjusted. It should therefore be interpreted as the result of that reported comparison, without assuming that it accounts for testing other outcomes or analyses. The registry record does not indicate whether other outcomes were measured but not posted, whether any adjustment was planned, or whether the primary endpoint was designated before data collection.

The primary outcome description notes that 7 participants were excluded from the analysis. Reasons for exclusion, the number with missing SGRQ measurements, and the handling of missing data are not reported in the registry record. No imputation strategy, sensitivity analysis, or complete-case definition is described. Without that information, it is not possible to assess whether the analysis depends on assumptions about why outcome data were unavailable.

The record also does not state whether the analysis followed intention-to-treat, per-protocol, or another analysis-population definition. Randomized assignment is reported, but the posted arm counts for the primary outcome do not by themselves establish which randomized participants were included or how exclusions were applied. The registry record does not report baseline outcome values or whether the primary comparison was adjusted for baseline measurements.

These omissions matter when evaluating how robust the estimated contrast may be to outcome selection, exclusions, and analysis choices. They do not change the numerical result that is posted, but they limit the ability to reconstruct the full analysis plan or assess the impact of missingness and multiplicity.

14. 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 2% reporting threshold.

The registry reports serious adverse events for both groups. For Standardized Respiratory Physiotherapy, 0 serious adverse events were reported among 62 participants at risk. For the control group, 0 serious adverse events were reported among 60 participants at risk. The posted death counts are also 0 in each group. The registry lists no top serious-event terms.

These are observed counts in the recorded groups, not evidence that the risk of a serious event is zero. When no events are recorded, the data still leave uncertainty about event rates that could occur in a larger population or over a different period of observation. The registry record does not report an adverse-event follow-up duration or detailed methods for collecting and classifying events, so those aspects cannot be evaluated from the posted figures.

The record also shows 0 other adverse events among 62 participants at risk in the physiotherapy group and among 60 in the control group. These counts should be read as the registry’s reported figures, rather than as a comprehensive description of every possible event. The information does not support a broader safety conclusion beyond the absence of reported events in these recorded counts.

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

The posted results show a lower average six-month SGRQ score in the Standardized Respiratory Physiotherapy group than in the control group: 29.6 compared with 38.0. Because higher scores indicate more limitations, the direction of this observed group difference favors fewer reported limitations on average in the physiotherapy arm. The estimated mean difference is 8.4 points, with a 95% confidence interval from 1.015 to 15.79 and an unadjusted p-value of 0.026.

This is a statistical description of the reported primary outcome, not a recommendation about treatment. The confidence interval reflects uncertainty in the average contrast under the analysis assumptions. It does not show how individual participants responded, establish that all participants benefited, or show that the observed contrast is clinically important. A clinical-importance threshold is not reported in the registry record.

The randomized design supports a comparison between assigned groups, but interpretation also depends on the analysis population and conduct. The primary outcome description says 7 participants were excluded, and the reasons and missing-data procedures are not reported. The registry record does not specify whether all randomized participants were analyzed as assigned or whether baseline measurements were used in an adjusted comparison. Those uncertainties limit the strength of conclusions that can be drawn from the posted summary statistics.

The registry hypothesis mentions additional topics, including mortality-predictive factors and economic impact. The posted primary result is the SGRQ score, and no secondary results are posted. The score result therefore does not answer every question named in the hypothesis. It also cannot establish effects beyond the participants, setting, outcome measure, and six-month timeframe reported in the record. The findings describe this trial’s posted comparison and should not be generalized automatically to other populations or care settings.

16. Why This Trial Matters Statistically

This trial is statistically notable because it evaluates a patient-reported continuous outcome in a randomized primary-care comparison. The SGRQ score captures respiratory symptoms and their impact on daily life, including activity limitations and overall well-being. Reporting group means and standard deviations makes it possible to see both the average contrast and the amount of variation among participants, while the confidence interval communicates uncertainty around the comparison.

The result also illustrates why effect size and statistical evidence answer different questions. The mean difference of 8.4 is expressed on the SGRQ scale, while the unadjusted p-value of 0.026 describes evidence against a no-difference model under the analysis assumptions. Neither alone determines whether a difference is clinically important. The registry record does not report a threshold for that judgment, so the measured contrast should be interpreted statistically and in the context of the score’s direction rather than assigned a clinical label that the record does not support.

Planning illustrations based on the observed effect show how anticipated effect size influences the number of participants needed for a future study under stated assumptions. They are not the original design justification, and they are not observed power. This distinction is important because a completed study’s results cannot substitute for a prospective sample-size rationale.

The record also highlights the value of complete reporting. The note that 7 participants were excluded, without reasons or a missing-data method, leaves uncertainty about the analyzed population. Details of multiplicity, baseline adjustment, and the original statistical plan are not reported. These gaps constrain reproducibility and interpretation even though the primary numerical comparison is available.

17. 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 leaves several trial-specific limitations unresolved. The primary outcome description states that 7 participants were excluded from analysis, but gives no reasons, timing, or account of how the exclusions were handled. The missing-data method and the analysis population definition are not reported. It is therefore unclear from the record whether the posted comparison includes all randomized participants or whether exclusions could have affected comparability between groups.

The title describes participants with mild COPD, while the hypothesis in the summary refers to moderate COPD. The record does not clarify this difference. It also describes the comparator intervention as a placebo primary-care procedure but calls the control-arm treatment usual clinical practice. These differences in wording make it important not to overstate the exact population or comparator beyond what the record says.

The intervention description is incomplete after describing the education session and the schedule of exercise sessions. Further details about delivery, adherence, or intervention fidelity are not reported in the registry record. The record does not report baseline SGRQ values, a change-from-baseline analysis, or a clinical-importance threshold for the score difference. It also does not specify the statistical test, any covariate adjustment, or a multiplicity plan.

The results are limited to the posted primary SGRQ comparison at six months. Although the summary hypothesis mentions additional outcomes and economic impact, no secondary results are posted. The record does not provide enough detail to assess those outcomes or determine whether they were measured as planned. These reporting gaps do not change the posted mean difference and interval, but they limit assessment of bias, reproducibility, and the broader scope of conclusions.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Effectiveness of Standardized Respiratory Physiotherapy in Primary Care (FREAP) — NCT01152762.
• Registry record last updated 2026-08-06; status last verified 2023-02.
• Results first posted 2026-08-06.
• 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.

21. Record Summary

NCT01152762 is a completed randomized, parallel-group trial with no masking, enrolling 129 participants with COPD. It compares Standardized Respiratory Physiotherapy in primary care with a control group described as usual clinical practice. The recorded start was 2007-09, and primary completion was 2008-07.

The primary outcome is the SGRQ score at six months. The reported means were 29.6 for the physiotherapy group and 38.0 for the control group; the mean difference was 8.4, with a 95% confidence interval from 1.015 to 15.79 and an unadjusted p-value of 0.026. The endpoint description notes that 7 participants were excluded from the analysis.

No secondary results are posted. The registry record does not report the original sample-size justification, detailed statistical analysis plan, missing-data approach, or multiplicity plan. Serious adverse-event and death counts were 0 in both groups.