Patient Perception Questionnaire Validation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Patient Perception Questionnaire Validation (NCT02067000), a registered phase not stated study. The primary outcome is To Determine the Association of the Participants Baseline PPQ (Patient Perception Questionnaire) Responses to Predict Adherence to CPAP Treatment at 90 Days..

2. Clinical Question

3. Trial Design

The study is titled “Patient Perception Questionnaire Validation.” The registry describes its purpose as validation of a questionnaire relating to CPAP use in people with OSA. The primary outcome asks whether participants’ baseline PPQ responses are associated with adherence to CPAP treatment at 90 days. The record gives the timeframe as baseline and 90 days. It also lists adherence to CPAP treatment and reliability of the PPQ among the secondary outcomes.

The registry lists enrollment as 217 and identifies Fisher and Paykel Healthcare as the sponsor. The study status is completed. The recorded start is 2011-04 and primary completion is 2012-02. These record details do not establish how many participants completed follow-up or contributed data to any particular analysis.

This is not described as a randomized controlled comparison. The registry record does not state allocation, and it does not identify a separate control group. Its intervention entry is “Obstructive Sleep Apnea,” classified as behavioral, while the brief summary focuses on questionnaire validation. That entry alone does not specify a behavioral treatment or establish that participants received a particular intervention.

The registry record does not report a detailed protocol, recruitment setting, eligibility criteria, follow-up procedures, or the statistical analysis plan. Although the record lists three outcome measures, it does not report an analysis for the primary outcome; no analyses are listed. The study design should therefore be read as a registry-described validation question, not as a documented comparative trial with reported estimates.

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

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 To Determine the Association of the Participants Baseline PPQ (Patient Perception Questionnaire) Responses to Predict Adherence to CPAP Treatment at 90 Days., measured over Baseline and 90 days.

The primary endpoint concerns the association between baseline responses to the Patient Perception Questionnaire and adherence to CPAP treatment at 90 days. The registry labels the measure as an “r value.” An association measure can describe how responses or scores vary in relation to an outcome; it does not, by itself, establish that one causes the other or that a questionnaire can accurately classify individual participants.

The PPQ is described as a custom questionnaire with 10 questions about perceptions of OSA and CPAP. The topics include how OSA affects life and is expected to continue, perceived need for CPAP, intention to use CPAP, spouse support or attitude, understanding of CPAP’s benefits, concern about using it, confidence using it, and the expectation that it will help treat OSA. The response ranges vary by question, and the meaning of a high response is not the same for every item. For example, the description assigns high values to both confidence with CPAP and lack of intention to use CPAP. Interpretations therefore require attention to each item’s stated direction rather than assuming that higher scores always represent a more favorable perception.

An association with later adherence is relevant to a validation question because it can indicate whether baseline perceptions relate to a subsequent behavior. However, the registry record does not report how adherence was defined, how questionnaire responses were combined or analyzed, or the observed association. It also does not report reliability results, despite listing reliability as a secondary outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is described as an “r value” for the association between baseline PPQ responses and CPAP adherence at 90 days. The registry record does not specify the exact correlation or association method, whether responses were analyzed item by item or combined, or how adherence was measured. No analysis results are listed. Methodological interpretation must therefore distinguish the stated endpoint from an analysis that can actually be evaluated.

What does an association measure tell the reader?

General statistical explanation: An association measure describes whether two measured characteristics vary together and, depending on the measure, the direction and strength of that relationship. It does not establish that one characteristic caused the other. In a prediction setting, an association can be informative but does not on its own show how accurately a tool predicts outcomes for individuals. Performance can also depend on calibration, discrimination, the definition of the outcome, and validation in an appropriate population.

In this record, the intended relationship is between baseline questionnaire responses and adherence at 90 days. The registry’s “r value” wording is not enough to determine the precise calculation. The record does not say whether adherence was represented as a continuous measure, a category, or another form. It also does not say whether a score was formed from multiple PPQ items. These details affect how an association estimate should be interpreted.

Why do the question-specific scales matter?

The questionnaire description gives different response ranges for its items and different meanings for high responses. Some items concern perceived impact or confidence; others concern intention not to use CPAP, concern, or a spouse’s negative attitude. A general statistical consideration is that combining items into a score may require a specified scoring rule, including decisions about direction and whether items are transformed. The registry record does not report a scoring rule or say whether any items were combined. It is therefore not possible to infer a total score or interpret a higher overall score.

Questionnaire validation can involve several distinct forms of evidence. An association with later adherence addresses one relationship with an external outcome. Reliability concerns consistency of measurement, but the record does not state which reliability procedure was used or report its result. Evidence for one property should not be treated as proof of all other measurement properties. In particular, association alone would not establish that the questionnaire measures every intended concept or performs well in other populations.

How should uncertainty be assessed?

General statistical explanation: A confidence interval expresses a range of estimates compatible with the data and the assumptions of the analysis. It helps readers assess precision, rather than relying only on whether a test crosses a significance threshold. The registry record reports no confidence interval for the primary association. Without an estimate and interval, neither magnitude nor precision can be judged. A p-value, even if one had been reported, would not replace the estimate or describe the practical size of an association.

The registry’s planning assumptions mention a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those assumptions are described for planning illustrations computed from an observed effect, not as a documented analysis plan for this validation study. The record does not report the observed effect needed to interpret such an illustration, nor does it state that the study itself used equal allocation or a two-arm randomized design. No sample-size justification or power calculation for the study is reported in the registry record. Planning illustrations, when present, are not observed power and do not convey the precision of an actual analysis.

What can be said about the statistical plan?

The registry record does not report whether analyses were adjusted, whether assumptions were checked, how repeated or missing measurements were handled, or how outcome definitions were applied. It does not identify a prespecified model, a primary scoring approach, or an analysis population. These omissions do not prove that no such methods were used; they mean that they are not reported in the registry record.

The record’s study description and endpoint label are useful for understanding the intended question. They cannot replace the analysis methods and results required to evaluate it. A reader would need the reported estimate, its uncertainty, the operational definition of adherence, questionnaire scoring details, and the analysis population to assess the strength and applicability of the evidence.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures, including the primary association question and secondary outcomes concerning adherence to CPAP treatment and PPQ reliability. It does not report how many individual statistical tests were conducted, which specific PPQ items were tested, or whether any adjustment for multiple comparisons was planned or used. No analyses are listed in the registry record. It is therefore not possible to assess multiplicity or determine whether any reported statistical significance would have been adjusted for multiple testing.

General statistical explanation: When many outcomes, questionnaire items, or subgroup comparisons are examined, the chance of finding an apparently notable result by chance can increase. A prespecified primary outcome and a transparent account of secondary analyses help readers distinguish confirmatory questions from exploratory ones. The registry record identifies a primary question but does not provide enough analysis detail to determine how it was implemented or how secondary analyses were handled.

Missing-data methods and analysis populations are also not reported. The registry lists enrollment as 217, but it does not state how many participants completed the 90-day assessment, had usable PPQ responses, or contributed to the primary outcome analysis. It does not describe withdrawals, missing questionnaire items, unavailable adherence data, or any method used to handle incomplete records. Enrollment should not be treated as an analysis denominator.

General statistical explanation: Missingness can affect an estimate when the availability of data is related to participant characteristics or outcomes. The appropriate interpretation depends on the amount and pattern of missingness, the analysis population, and the assumptions behind any method used. Since those details are not reported in the registry record, the impact of missing data cannot be assessed.

11. 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’s adverse-event entry lists the OSA group with 217 at risk and 0 affected for serious adverse events. It also lists 217 at risk and 0 affected for other adverse events. No serious adverse-event terms are listed. These are registry entries for the recorded group; they do not establish how adverse events were collected, monitored, defined, or attributed.

A zero in a registry summary means that no affected participants are recorded in that entry. It should not be read as proof that no event occurred outside the record’s collection or reporting process, nor does it demonstrate the absence of risk. The record does not provide event narratives, exposure details, follow-up completeness, or information about adjudication. It also does not explain how the adverse-event group relates to the questionnaire-validation analyses.

These figures should be interpreted separately from the primary endpoint. The primary question concerns association between baseline PPQ responses and adherence at 90 days; the adverse-event entries do not answer that question. Nor do these entries constitute a treatment comparison, since no comparator is described and the study is not reported as a randomized comparison.

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

This registry record is useful for identifying the study’s stated purpose: assessing a custom questionnaire about OSA and CPAP in relation to adherence at 90 days, with reliability also listed as a secondary outcome. It describes the themes covered by the questionnaire and identifies the intended primary association measure as an “r value.” Those details clarify the question the study set out to address.

The record does not report the primary association estimate, its precision, or the results for adherence and reliability. It therefore does not establish whether baseline perceptions were associated with later adherence, how strong any relationship was, or whether the questionnaire was reliable. No conclusion about predictive accuracy or validation success can be reached from the stated objectives alone.

The study also does not provide a randomized comparator or a documented allocation method. Even if an association estimate were available, an observational relationship between baseline perceptions and later behavior would not show that one caused the other. It would not establish that modifying a perception changes adherence, or that CPAP has a particular treatment effect.

The registry entry for enrollment does not tell readers how many participants contributed to each endpoint. The record does not report follow-up completion, missing-data handling, the adherence definition, or the PPQ scoring approach. These details are central to judging what an estimate would represent and how broadly it could be applied.

The adverse-event entries record zero affected participants in the listed categories, but the record does not provide enough collection and follow-up detail to interpret those entries as proof of no risk. More broadly, absence of reported primary results is not evidence that the questionnaire has no relationship with adherence; it means that the registry record does not report the evidence needed to answer the question.

13. Why This Trial Matters Statistically

Questionnaires about beliefs, confidence, concerns, and social support can be used to describe aspects of a participant’s experience that are not captured by a clinical measurement alone. A validation question asks whether those responses behave as expected in relation to an outcome of interest. In this study, the registry’s stated focus is the relationship between baseline perceptions and CPAP adherence at 90 days.

The statistical distinction between a research objective and a reported result is especially important in validation work. Naming an intended association does not show that the measure predicts behavior, and a single association would not establish every aspect of validity or reliability. Clear reporting of item scoring, outcome definitions, estimates, uncertainty, and analysis populations is needed to understand what the evidence supports.

The PPQ description also illustrates why questionnaire items need careful interpretation. The stated direction of high responses differs across topics: high values can correspond to confidence or support, but also to concern or lack of intention to use CPAP. Without a reported scoring rule, readers should not assume that the items form one scale or that higher responses have one consistent meaning.

This record matters statistically as a case in separating design intent from accessible evidence. It identifies a clinically relevant validation question, but the registry does not list the analyses or results required to evaluate the answer. Recognizing that boundary prevents an objective, enrollment entry, or adverse-event summary from being mistaken for evidence about predictive performance.

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 important limitation of the registry record is that it does not report the primary association estimate or any analysis results. The intended “r value” is named, but its value, uncertainty, and statistical interpretation are not available in the registry record. The listed secondary outcomes likewise have no reported results.

The endpoint is not operationally detailed. The record does not define adherence to CPAP, explain how adherence was measured, or state whether the primary analysis used individual PPQ items or a combined score. Although it describes the subject matter and response ranges of the 10 questions, it does not give a scoring algorithm. The differing meanings of high responses make that omission important for interpretation.

The design description does not identify a comparator or allocation method. The registry’s notes specify that the study is not a randomized comparison. The listed intervention entry is named “Obstructive Sleep Apnea” and classified as behavioral, but no behavioral procedure is described. The record therefore does not support interpreting the study as a defined intervention trial.

Participant flow and analysis denominators are not reported. The enrollment entry does not establish how many participants posted complete baseline responses, had adherence information at 90 days, or were included in an analysis. The record also does not describe missing-data procedures, eligibility criteria, participant characteristics, adjustment methods, or handling of multiple outcomes.

Finally, the registry does not report a statistical analysis plan or sample-size justification for the study. The planning assumptions recorded for illustrations are not a substitute for those details. These reporting limitations constrain what can be concluded from the registry record; they do not establish that unreported methods or results do not exist elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Patient Perception Questionnaire Validation — NCT02067000.
• Registry record last updated 2020-07-15; status last verified 2020-07.
• Results first posted 2020-07-15.
• 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

The registry record describes a completed study titled “Patient Perception Questionnaire Validation,” sponsored by Fisher and Paykel Healthcare. It lists OSA as the condition, enrollment of 217, a recorded start of 2011-04, and primary completion in 2012-02.

The primary question concerns association between baseline PPQ responses and CPAP adherence at 90 days. The PPQ is described as a custom 10-question measure covering perceptions of OSA, CPAP, confidence, concern, and social support. Adherence and questionnaire reliability are listed as secondary outcomes.

No comparator or allocation method is reported, and the study is not described as a randomized comparison. The registry record does not list analyses or report the primary estimate, reliability results, analysis populations, or missing-data methods. Its adverse-event entries list 0 affected participants in the serious and other adverse-event categories. The record therefore describes the intended validation question but does not provide results with which to assess it.